[PATCH] clocksource: dw_apb_timer_of: support timer-based delay

On 10/30/2015 12:09 PM, Jisheng Zhang wrote:

Dear Daniel,

On Fri, 30 Oct 2015 11:44:46 +0100
Daniel Lezcano <daniel.lezcano@....> wrote:

quoted

On 10/30/2015 09:27 AM, Jisheng Zhang wrote:

quoted

Implement an ARM delay timer to be used for udelay(). This allows us to
skip the delay loop calibration at boot on Marvell BG2, BG2Q, BG2CD
platforms. And after this patch, udelay() will be unaffected by CPU
frequency changes.

Signed-off-by: Jisheng Zhang <redacted>
---
   drivers/clocksource/Kconfig           | 10 ++++++++++
   drivers/clocksource/dw_apb_timer_of.c | 16 ++++++++++++++++
   2 files changed, 26 insertions(+)

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index a7726db..7b081805 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig

@@ -29,6 +29,16 @@ config DW_APB_TIMER_OF
   	select DW_APB_TIMER
   	select CLKSRC_OF

+config DW_APB_TIMER_BASED_DELAY
+	bool "DW APB timer based delay"
+	depends on ARM && DW_APB_TIMER_OF
+	default n
+	help
+	  This option enables support for using the DW APB timer to
+	  implement timer-based delay. It is useful for skiping the
+	  delay loop calibration at boot on some platforms. And the
+	  udelay() will be unaffected by CPU frequency changes.
+

Why do you want it to be optional ?

Because in some platforms which has arm arch timer, this dw apb timer
delay isn't needed, the arch timer is better. So we want it be optional
so that the platforms which need this feature select it manually when config
the kernel.

Correct me if I am wrong. If you have the arch timer, you don't need the 
dw apb timer at all, no ? So the selection would be arch arm timer *or* 
dw_apb_timer ? not arch_arm_timer for delay and dw_apb_timer for 
clockevents, right ?


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