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acpi-dma: Add support for "dma-names" device property 

The current implementation hard codes the two supported channels so that
"tx" is always 0 and "rx" is always 1. This is because there has been no
suitable way in ACPI to name resources.

With _DSD device properties we can finally do this:

	Device (SPI1) {
	    Name (_CRS, ResourceTemplate () {
	        ...
	        FixedDMA (0x0000, 0x0000, Width32bit)
	        FixedDMA (0x0001, 0x0001, Width32bit)
	    })

	    Name (_DSD, Package () {
	        ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
	        Package () {
	            Package () {"dma-names", Package () {"tx", "rx"}}
	        },
	    })
	}

The names "tx" and "rx" now provide index of the FixedDMA resource in
question.

Modify acpi_dma_request_slave_chan_by_name() so that it looks for
"dma-names" property first and only then fall back using hardcoded indices.

The DT "dma-names" binding that we reuse for ACPI is documented in
Documentation/devicetree/bindings/dma/dma.txt.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
hifive-unleashed-5.1
Mika Westerberg 2015-09-14 17:37:36 +03:00 committed by Rafael J. Wysocki
parent 3f5c8d3187
commit 3f4232ee8b
1 changed files with 16 additions and 7 deletions
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23
drivers/dma/acpi-dma.c
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@ -21,6 +21,7 @@
#include <linux/ioport.h>
#include <linux/acpi.h>
#include <linux/acpi_dma.h>
#include <linux/property.h>
static LIST_HEAD(acpi_dma_list);
static DEFINE_MUTEX(acpi_dma_lock);
@ -413,21 +414,29 @@ EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_index);
* translate the names "tx" and "rx" here based on the most common case where
* the first FixedDMA descriptor is TX and second is RX.
*
* If the device has "dma-names" property the FixedDMA descriptor indices
* are retrieved based on those. Otherwise the function falls back using
* hardcoded indices.
*
* Return:
* Pointer to appropriate dma channel on success or an error pointer.
*/
struct dma_chan *acpi_dma_request_slave_chan_by_name(struct device *dev,
const char *name)
{
size_t index;
int index;
if (!strcmp(name, "tx"))
index = 0;
else if (!strcmp(name, "rx"))
index = 1;
else
return ERR_PTR(-ENODEV);
index = device_property_match_string(dev, "dma-names", name);
if (index < 0) {
if (!strcmp(name, "tx"))
index = 0;
else if (!strcmp(name, "rx"))
index = 1;
else
return ERR_PTR(-ENODEV);
}
dev_dbg(dev, "found DMA channel \"%s\" at index %d\n", name, index);
return acpi_dma_request_slave_chan_by_index(dev, index);
}
EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_name);