![David Howells](/assets/img/avatar_default.png)
Maintain a per-CPU global "struct pt_regs *" variable which can be used instead of passing regs around manually through all ~1800 interrupt handlers in the Linux kernel. The regs pointer is used in few places, but it potentially costs both stack space and code to pass it around. On the FRV arch, removing the regs parameter from all the genirq function results in a 20% speed up of the IRQ exit path (ie: from leaving timer_interrupt() to leaving do_IRQ()). Where appropriate, an arch may override the generic storage facility and do something different with the variable. On FRV, for instance, the address is maintained in GR28 at all times inside the kernel as part of general exception handling. Having looked over the code, it appears that the parameter may be handed down through up to twenty or so layers of functions. Consider a USB character device attached to a USB hub, attached to a USB controller that posts its interrupts through a cascaded auxiliary interrupt controller. A character device driver may want to pass regs to the sysrq handler through the input layer which adds another few layers of parameter passing. I've build this code with allyesconfig for x86_64 and i386. I've runtested the main part of the code on FRV and i386, though I can't test most of the drivers. I've also done partial conversion for powerpc and MIPS - these at least compile with minimal configurations. This will affect all archs. Mostly the changes should be relatively easy. Take do_IRQ(), store the regs pointer at the beginning, saving the old one: struct pt_regs *old_regs = set_irq_regs(regs); And put the old one back at the end: set_irq_regs(old_regs); Don't pass regs through to generic_handle_irq() or __do_IRQ(). In timer_interrupt(), this sort of change will be necessary: - update_process_times(user_mode(regs)); - profile_tick(CPU_PROFILING, regs); + update_process_times(user_mode(get_irq_regs())); + profile_tick(CPU_PROFILING); I'd like to move update_process_times()'s use of get_irq_regs() into itself, except that i386, alone of the archs, uses something other than user_mode(). Some notes on the interrupt handling in the drivers: (*) input_dev() is now gone entirely. The regs pointer is no longer stored in the input_dev struct. (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does something different depending on whether it's been supplied with a regs pointer or not. (*) Various IRQ handler function pointers have been moved to type irq_handler_t. Signed-Off-By: David Howells <dhowells@redhat.com> (cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
318 lines
8.6 KiB
C
318 lines
8.6 KiB
C
/*
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* USB Serial Converter Generic functions
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*
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* Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version
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* 2 as published by the Free Software Foundation.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/slab.h>
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#include <linux/tty.h>
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#include <linux/tty_flip.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/usb.h>
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#include <linux/usb/serial.h>
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#include <asm/uaccess.h>
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static int debug;
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#ifdef CONFIG_USB_SERIAL_GENERIC
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static __u16 vendor = 0x05f9;
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static __u16 product = 0xffff;
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module_param(vendor, ushort, 0);
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MODULE_PARM_DESC(vendor, "User specified USB idVendor");
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module_param(product, ushort, 0);
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MODULE_PARM_DESC(product, "User specified USB idProduct");
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static struct usb_device_id generic_device_ids[2]; /* Initially all zeroes. */
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/* All of the device info needed for the Generic Serial Converter */
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struct usb_serial_driver usb_serial_generic_device = {
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.driver = {
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.owner = THIS_MODULE,
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.name = "generic",
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},
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.id_table = generic_device_ids,
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.num_interrupt_in = NUM_DONT_CARE,
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.num_bulk_in = NUM_DONT_CARE,
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.num_bulk_out = NUM_DONT_CARE,
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.num_ports = 1,
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.shutdown = usb_serial_generic_shutdown,
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};
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/* we want to look at all devices, as the vendor/product id can change
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* depending on the command line argument */
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static struct usb_device_id generic_serial_ids[] = {
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{.driver_info = 42},
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{}
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};
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static int generic_probe(struct usb_interface *interface,
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const struct usb_device_id *id)
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{
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const struct usb_device_id *id_pattern;
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id_pattern = usb_match_id(interface, generic_device_ids);
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if (id_pattern != NULL)
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return usb_serial_probe(interface, id);
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return -ENODEV;
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}
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static struct usb_driver generic_driver = {
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.name = "usbserial_generic",
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.probe = generic_probe,
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.disconnect = usb_serial_disconnect,
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.id_table = generic_serial_ids,
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.no_dynamic_id = 1,
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};
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#endif
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int usb_serial_generic_register (int _debug)
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{
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int retval = 0;
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debug = _debug;
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#ifdef CONFIG_USB_SERIAL_GENERIC
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generic_device_ids[0].idVendor = vendor;
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generic_device_ids[0].idProduct = product;
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generic_device_ids[0].match_flags = USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_PRODUCT;
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/* register our generic driver with ourselves */
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retval = usb_serial_register (&usb_serial_generic_device);
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if (retval)
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goto exit;
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retval = usb_register(&generic_driver);
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if (retval)
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usb_serial_deregister(&usb_serial_generic_device);
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exit:
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#endif
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return retval;
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}
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void usb_serial_generic_deregister (void)
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{
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#ifdef CONFIG_USB_SERIAL_GENERIC
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/* remove our generic driver */
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usb_deregister(&generic_driver);
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usb_serial_deregister (&usb_serial_generic_device);
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#endif
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}
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int usb_serial_generic_open (struct usb_serial_port *port, struct file *filp)
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{
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struct usb_serial *serial = port->serial;
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int result = 0;
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dbg("%s - port %d", __FUNCTION__, port->number);
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/* force low_latency on so that our tty_push actually forces the data through,
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otherwise it is scheduled, and with high data rates (like with OHCI) data
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can get lost. */
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if (port->tty)
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port->tty->low_latency = 1;
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/* if we have a bulk interrupt, start reading from it */
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if (serial->num_bulk_in) {
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/* Start reading from the device */
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usb_fill_bulk_urb (port->read_urb, serial->dev,
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usb_rcvbulkpipe(serial->dev, port->bulk_in_endpointAddress),
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port->read_urb->transfer_buffer,
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port->read_urb->transfer_buffer_length,
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((serial->type->read_bulk_callback) ?
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serial->type->read_bulk_callback :
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usb_serial_generic_read_bulk_callback),
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port);
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result = usb_submit_urb(port->read_urb, GFP_KERNEL);
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if (result)
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dev_err(&port->dev, "%s - failed resubmitting read urb, error %d\n", __FUNCTION__, result);
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}
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return result;
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}
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EXPORT_SYMBOL_GPL(usb_serial_generic_open);
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static void generic_cleanup (struct usb_serial_port *port)
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{
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struct usb_serial *serial = port->serial;
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dbg("%s - port %d", __FUNCTION__, port->number);
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if (serial->dev) {
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/* shutdown any bulk reads that might be going on */
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if (serial->num_bulk_out)
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usb_kill_urb(port->write_urb);
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if (serial->num_bulk_in)
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usb_kill_urb(port->read_urb);
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}
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}
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void usb_serial_generic_close (struct usb_serial_port *port, struct file * filp)
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{
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dbg("%s - port %d", __FUNCTION__, port->number);
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generic_cleanup (port);
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}
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int usb_serial_generic_write(struct usb_serial_port *port, const unsigned char *buf, int count)
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{
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struct usb_serial *serial = port->serial;
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int result;
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unsigned char *data;
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dbg("%s - port %d", __FUNCTION__, port->number);
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if (count == 0) {
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dbg("%s - write request of 0 bytes", __FUNCTION__);
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return (0);
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}
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/* only do something if we have a bulk out endpoint */
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if (serial->num_bulk_out) {
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spin_lock_bh(&port->lock);
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if (port->write_urb_busy) {
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spin_unlock_bh(&port->lock);
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dbg("%s - already writing", __FUNCTION__);
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return 0;
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}
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port->write_urb_busy = 1;
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spin_unlock_bh(&port->lock);
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count = (count > port->bulk_out_size) ? port->bulk_out_size : count;
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memcpy (port->write_urb->transfer_buffer, buf, count);
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data = port->write_urb->transfer_buffer;
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usb_serial_debug_data(debug, &port->dev, __FUNCTION__, count, data);
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/* set up our urb */
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usb_fill_bulk_urb (port->write_urb, serial->dev,
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usb_sndbulkpipe (serial->dev,
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port->bulk_out_endpointAddress),
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port->write_urb->transfer_buffer, count,
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((serial->type->write_bulk_callback) ?
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serial->type->write_bulk_callback :
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usb_serial_generic_write_bulk_callback), port);
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/* send the data out the bulk port */
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port->write_urb_busy = 1;
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result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
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if (result) {
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dev_err(&port->dev, "%s - failed submitting write urb, error %d\n", __FUNCTION__, result);
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/* don't have to grab the lock here, as we will retry if != 0 */
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port->write_urb_busy = 0;
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} else
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result = count;
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return result;
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}
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/* no bulk out, so return 0 bytes written */
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return 0;
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}
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int usb_serial_generic_write_room (struct usb_serial_port *port)
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{
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struct usb_serial *serial = port->serial;
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int room = 0;
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dbg("%s - port %d", __FUNCTION__, port->number);
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if (serial->num_bulk_out) {
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if (!(port->write_urb_busy))
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room = port->bulk_out_size;
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}
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dbg("%s - returns %d", __FUNCTION__, room);
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return (room);
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}
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int usb_serial_generic_chars_in_buffer (struct usb_serial_port *port)
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{
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struct usb_serial *serial = port->serial;
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int chars = 0;
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dbg("%s - port %d", __FUNCTION__, port->number);
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if (serial->num_bulk_out) {
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if (port->write_urb_busy)
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chars = port->write_urb->transfer_buffer_length;
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}
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dbg("%s - returns %d", __FUNCTION__, chars);
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return (chars);
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}
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void usb_serial_generic_read_bulk_callback (struct urb *urb)
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{
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struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
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struct usb_serial *serial = port->serial;
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struct tty_struct *tty;
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unsigned char *data = urb->transfer_buffer;
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int result;
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dbg("%s - port %d", __FUNCTION__, port->number);
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if (urb->status) {
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dbg("%s - nonzero read bulk status received: %d", __FUNCTION__, urb->status);
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return;
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}
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usb_serial_debug_data(debug, &port->dev, __FUNCTION__, urb->actual_length, data);
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tty = port->tty;
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if (tty && urb->actual_length) {
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tty_buffer_request_room(tty, urb->actual_length);
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tty_insert_flip_string(tty, data, urb->actual_length);
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tty_flip_buffer_push(tty);
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}
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/* Continue trying to always read */
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usb_fill_bulk_urb (port->read_urb, serial->dev,
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usb_rcvbulkpipe (serial->dev,
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port->bulk_in_endpointAddress),
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port->read_urb->transfer_buffer,
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port->read_urb->transfer_buffer_length,
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((serial->type->read_bulk_callback) ?
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serial->type->read_bulk_callback :
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usb_serial_generic_read_bulk_callback), port);
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result = usb_submit_urb(port->read_urb, GFP_ATOMIC);
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if (result)
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dev_err(&port->dev, "%s - failed resubmitting read urb, error %d\n", __FUNCTION__, result);
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}
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EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);
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void usb_serial_generic_write_bulk_callback (struct urb *urb)
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{
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struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
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dbg("%s - port %d", __FUNCTION__, port->number);
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port->write_urb_busy = 0;
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if (urb->status) {
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dbg("%s - nonzero write bulk status received: %d", __FUNCTION__, urb->status);
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return;
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}
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usb_serial_port_softint(port);
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}
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EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback);
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void usb_serial_generic_shutdown (struct usb_serial *serial)
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{
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int i;
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dbg("%s", __FUNCTION__);
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/* stop reads and writes on all ports */
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for (i=0; i < serial->num_ports; ++i) {
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generic_cleanup(serial->port[i]);
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}
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}
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