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ARM: 6376/1: plat-nomadik: MTU: Change prescaler limit and comment updates 

The prescaler 16 is now used only when the timer runs at 32 MHz
or more. Some comment updates as well.

Acked-by: Alessandro Rubini <rubini@unipv.it>
Signed-off-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
hifive-unleashed-5.1
Linus Walleij 2010-09-13 13:40:04 +01:00 committed by Russell King
parent 99f76891a3
commit a0719f52d9
1 changed files with 10 additions and 7 deletions
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17
arch/arm/plat-nomadik/timer.c
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@ -1,5 +1,5 @@
/*
* linux/arch/arm/mach-nomadik/timer.c
* linux/arch/arm/plat-nomadik/timer.c
*
* Copyright (C) 2008 STMicroelectronics
* Copyright (C) 2010 Alessandro Rubini
@ -75,7 +75,7 @@ static void nmdk_clkevt_mode(enum clock_event_mode mode,
cr = readl(mtu_base + MTU_CR(1));
writel(0, mtu_base + MTU_LR(1));
writel(cr | MTU_CRn_ENA, mtu_base + MTU_CR(1));
writel(0x2, mtu_base + MTU_IMSC);
writel(1 << 1, mtu_base + MTU_IMSC);
break;
case CLOCK_EVT_MODE_SHUTDOWN:
case CLOCK_EVT_MODE_UNUSED:
@ -131,7 +131,7 @@ void __init nmdk_timer_init(void)
{
unsigned long rate;
struct clk *clk0;
u32 cr;
u32 cr = MTU_CRn_32BITS;
clk0 = clk_get_sys("mtu0", NULL);
BUG_ON(IS_ERR(clk0));
@ -139,12 +139,15 @@ void __init nmdk_timer_init(void)
clk_enable(clk0);
/*
* Tick rate is 2.4MHz for Nomadik and 110MHz for ux500:
* use a divide-by-16 counter if it's more than 16MHz
* Tick rate is 2.4MHz for Nomadik and 2.4Mhz, 100MHz or 133 MHz
* for ux500.
* Use a divide-by-16 counter if the tick rate is more than 32MHz.
* At 32 MHz, the timer (with 32 bit counter) can be programmed
* to wake-up at a max 127s a head in time. Dividing a 2.4 MHz timer
* with 16 gives too low timer resolution.
*/
cr = MTU_CRn_32BITS;;
rate = clk_get_rate(clk0);
if (rate > 16 << 20) {
if (rate > 32000000) {
rate /= 16;
cr |= MTU_CRn_PRESCALE_16;
} else {