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linux/arch/arm
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Uwe Kleine-König fb3174e4ad ARM: ixp4xx: fix timer latch calculation 
In commit f0402f9b47 ("ARM: ixp4xx: stop using <mach/timex.h>")
I didn't intend to implement a functional change, but as Olof noticed I
failed---at least a bit. Before this commit the following was used to
determine the latch value used:

	#define IXP4XX_TIMER_FREQ 66666000
	#define CLOCK_TICK_RATE \
		(((IXP4XX_TIMER_FREQ / HZ & ~IXP4XX_OST_RELOAD_MASK) + 1) * HZ)
	#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ)

The complicated calculation was done "b/c the timer register ignores the
bottom 2 bits of the LATCH value." With HZ=100 CLOCK_TICK_RATE used to
calculate to 66666100 and so LATCH to 666661. In ixp4xx_set_mode the
term

	LATCH & ~IXP4XX_OST_RELOAD_MASK

was used to write to the relevant register (with IXP4XX_OST_RELOAD_MASK
being 3) and so effectively 666660 was used.

In commit f0402f9b47 I translated that to:

	#define IXP4XX_TIMER_FREQ 66666000
	#define IXP4XX_LATCH DIV_ROUND_CLOSEST(IXP4XX_TIMER_FREQ, HZ)

which results in the same register writes, but still doesn't bear in
mind that the two least significant bits cannot be specified (which is
relevant only when HZ or IXP4XX_TIMER_FREQ are changed).

Instead of reverting back to the old approach use a more obvious and
also more correct way to calculate LATCH. (Regarding the more
correct claim: With IXP4XX_TIMER_FREQ == 66665999, the old code resulted
in LATCH = 666657 corresponding to a cycle time of 0.009999940149400597
seconds (error: -6.0e-8 s) while the new approach results in LATCH =
666660 and so a cycle time of 0.010000000150001503 seconds
(error: 1.5e-10 s).)

Fixes: f0402f9b47 ("ARM: ixp4xx: stop using <mach/timex.h>")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
2014-02-18 21:23:19 +01:00
..
boot ARM: u300: Remove '0x's from U300 DTS file 2013-11-26 21:00:21 +01:00
common Merge branch 'next' of git://git.infradead.org/users/vkoul/slave-dma 2013-11-20 13:20:24 -08:00
configs watchdog: sirf: add watchdog driver of CSR SiRFprimaII and SiRFatlasVI 2013-11-17 19:37:23 +01:00
crypto ARM: add .gitignore entry for aesbs-core.S 2013-10-07 15:43:53 +01:00
include ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
kernel ARM: 7892/1: Fix warning for V7M builds 2013-11-19 00:41:03 +00:00
kvm Fix percpu vmalloc allocations 2013-11-19 10:43:05 +02:00
lib ARM: 7893/1: bitops: only emit .arch_extension mp if CONFIG_SMP 2013-11-20 23:05:53 +00:00
mach-at91 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-bcm BCM changes for 3.13/soc. A number of cleanup related changes. 2013-10-30 14:03:39 -07:00
mach-bcm2835 Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-11-12 10:02:59 +09:00
mach-clps711x ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-cns3xxx
mach-davinci ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-dove ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-ebsa110 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-ep93xx ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-exynos ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-footbridge ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-gemini ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-highbank ARM: SoC fixes for 3.13 merge window 2013-11-16 12:45:55 -08:00
mach-imx Merge branch 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2013-11-18 15:50:07 -08:00
mach-integrator ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-iop13xx ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-iop32x ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-iop33x ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-ixp4xx ARM: ixp4xx: fix timer latch calculation 2014-02-18 21:23:19 +01:00
mach-keystone DeviceTree updates for 3.13. This is a bit larger pull request than 2013-11-12 16:52:17 +09:00
mach-kirkwood ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-ks8695 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-lpc32xx ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-mmp ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-msm ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-mv78xx0 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-mvebu ARM: mvebu: support running big-endian 2013-10-19 20:46:34 +01:00
mach-mxs ARM: SoC DT updates for 3.13 2013-11-11 17:34:56 +09:00
mach-netx ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-nomadik Merge branch 'clk-of-init-v2_for-3.13' of https://github.com/shesselba/linux-dove into next/cleanup 2013-10-07 09:47:31 -07:00
mach-nspire ARM: nspire: remove custom .init_time hook 2013-09-29 21:09:37 +02:00
mach-omap1 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-omap2 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-orion5x ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-picoxcell
mach-prima2 ARM: prima2: remove custom .init_time hook 2013-09-29 21:09:38 +02:00
mach-pxa ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-realview ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-rockchip ARM: SoC board updates for 3.13 2013-11-11 16:57:16 +09:00
mach-rpc ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-s3c24xx ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-s3c64xx ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-s5p64x0 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-s5pc100 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-s5pv210 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-sa1100 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-shmobile ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-socfpga ARM: drop explicit selection of HAVE_CLK and CLKDEV_LOOKUP 2013-10-07 10:41:32 -07:00
mach-spear ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-sti ARM: SoC fixes for 3.13 merge window 2013-11-16 12:45:55 -08:00
mach-sunxi ARM: sunxi: remove .init_time hooks 2013-10-28 10:19:45 -07:00
mach-tegra ARM: SoC fixes for 3.13 merge window 2013-11-16 12:45:55 -08:00
mach-u300 ARM: u300: fix timekeeping when periodic mode is used 2013-11-26 21:00:21 +01:00
mach-ux500 ACPI and power management updates for 3.13-rc1 2013-11-14 13:41:48 +09:00
mach-versatile ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-vexpress ACPI and power management updates for 3.13-rc1 2013-11-14 13:41:48 +09:00
mach-virt
mach-vt8500 ARM: drop explicit selection of HAVE_CLK and CLKDEV_LOOKUP 2013-10-07 10:41:32 -07:00
mach-w90x900 ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
mach-zynq ACPI and power management updates for 3.13-rc1 2013-11-14 13:41:48 +09:00
mm Merge branch 'fixes' of git://git.linaro.org/people/rmk/linux-arm 2013-11-22 09:56:51 -08:00
net Merge branch 'devel-stable' into for-next 2013-11-12 10:58:59 +00:00
nwfpe
oprofile
plat-iop ARM: plat-iop: move the GPIO driver to drivers/gpio 2013-09-20 23:03:36 +02:00
plat-omap ARM: drop <mach/timex.h> for !ARCH_MULTIPLATFORM, too 2013-12-20 17:17:16 +01:00
plat-orion
plat-pxa
plat-samsung pwm: Changes for v3.13-rc1 2013-11-16 12:21:40 -08:00
plat-versatile ARM: vexpress: add big endian support 2013-10-19 20:46:34 +01:00
tools
vfp ARM: 7873/1: vfp: clear vfp_current_hw_state for dying cpu 2013-10-30 22:10:10 +00:00
xen Merge remote-tracking branch 'stefano/swiotlb-xen-9.1' into stable/for-linus-3.13 2013-11-08 16:10:48 -05:00
Kconfig Merge branch 'fixes' of git://git.linaro.org/people/rmk/linux-arm 2013-11-22 09:56:51 -08:00
Kconfig-nommu
Kconfig.debug Merge branch 'for-linus' of git://git.linaro.org/people/rmk/linux-arm 2013-11-14 08:51:29 +09:00
Makefile Merge branch 'for-linus' of git://git.linaro.org/people/rmk/linux-arm 2013-11-14 08:51:29 +09:00