On Tue, May 8, 2012 at 3:47 PM, AnilKumar, Chimata [off-list ref] wrote:

On Mon, May 07, 2012 at 10:51:53, J, KEERTHY wrote:

quoted

On Fri, May 4, 2012 at 2:42 PM, AnilKumar, Chimata [off-list ref] wrote:

quoted

On Thu, Apr 26, 2012 at 23:10:36, J, KEERTHY wrote:

quoted

From: Jean Pihet <redacted>

Now that omap_test_timeout is only accessible from mach-omap2/,
introduce a similar function for SR.

This change makes the SmartReflex implementation ready for the move
to drivers/.

Signed-off-by: Jean Pihet <redacted>
Signed-off-by: J Keerthy <j-keerthy@ti.com>
---
?arch/arm/mach-omap2/smartreflex.c | ? 12 ++++++------
?include/linux/power/smartreflex.h | ? 23 ++++++++++++++++++++++-
?2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/arch/arm/mach-omap2/smartreflex.c b/arch/arm/mach-omap2/smartreflex.c
index d859277..acef08d 100644
--- a/arch/arm/mach-omap2/smartreflex.c
+++ b/arch/arm/mach-omap2/smartreflex.c

@@ -289,9 +289,9 @@ static void sr_v1_disable(struct omap_sr *sr)

? ? ? ?* Wait for SR to be disabled.
? ? ? ?* wait until ERRCONFIG.MCUDISACKINTST = 1. Typical latency is 1us.
? ? ? ?*/
- ? ? omap_test_timeout((sr_read_reg(sr, ERRCONFIG_V1) &
- ? ? ? ? ? ? ? ? ? ? ERRCONFIG_MCUDISACKINTST), SR_DISABLE_TIMEOUT,
- ? ? ? ? ? ? ? ? ? ? timeout);
+ ? ? sr_test_cond_timeout((sr_read_reg(sr, ERRCONFIG_V1) &
+ ? ? ? ? ? ? ? ? ? ? ? ? ?ERRCONFIG_MCUDISACKINTST), SR_DISABLE_TIMEOUT,
+ ? ? ? ? ? ? ? ? ? ? ? ? ?timeout);

? ? ? if (timeout >= SR_DISABLE_TIMEOUT)
? ? ? ? ? ? ? dev_warn(&sr->pdev->dev, "%s: Smartreflex disable timedout\n",

@@ -334,9 +334,9 @@ static void sr_v2_disable(struct omap_sr *sr)

? ? ? ?* Wait for SR to be disabled.
? ? ? ?* wait until IRQSTATUS.MCUDISACKINTST = 1. Typical latency is 1us.
? ? ? ?*/
- ? ? omap_test_timeout((sr_read_reg(sr, IRQSTATUS) &
- ? ? ? ? ? ? ? ? ? ? IRQSTATUS_MCUDISABLEACKINT), SR_DISABLE_TIMEOUT,
- ? ? ? ? ? ? ? ? ? ? timeout);
+ ? ? sr_test_cond_timeout((sr_read_reg(sr, IRQSTATUS) &
+ ? ? ? ? ? ? ? ? ? ? ? ? ?IRQSTATUS_MCUDISABLEACKINT), SR_DISABLE_TIMEOUT,
+ ? ? ? ? ? ? ? ? ? ? ? ? ?timeout);

? ? ? if (timeout >= SR_DISABLE_TIMEOUT)
? ? ? ? ? ? ? dev_warn(&sr->pdev->dev, "%s: Smartreflex disable timedout\n",

diff --git a/include/linux/power/smartreflex.h b/include/linux/power/smartreflex.h
index 884eaee..78b795e 100644
--- a/include/linux/power/smartreflex.h
+++ b/include/linux/power/smartreflex.h

@@ -22,7 +22,7 @@

?#include <linux/types.h>
?#include <linux/platform_device.h>
-
+#include <linux/delay.h>
?#include <plat/voltage.h>

?/*

@@ -168,6 +168,27 @@ struct omap_sr {

?};

?/**
+ * test_cond_timeout - busy-loop, testing a condition
+ * @cond: condition to test until it evaluates to true
+ * @timeout: maximum number of microseconds in the timeout
+ * @index: loop index (integer)
+ *
+ * Loop waiting for @cond to become true or until at least @timeout
+ * microseconds have passed. ?To use, define some integer @index in the
+ * calling code. ?After running, if @index == @timeout, then the loop has
+ * timed out.
+ *
+ * Copied from omap_test_timeout */
+#define sr_test_cond_timeout(cond, timeout, index) ? ? ? ? ? \
+({ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? \
+ ? ? for (index = 0; index < timeout; index++) { ? ? ? ? ? ? \
+ ? ? ? ? ? ? if (cond) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? \
+ ? ? ? ? ? ? ? ? ? ? break; ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?\
+ ? ? ? ? ? ? udelay(1); ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?\
+ ? ? } ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? \
+})

I think we can use time_after()/time_before() APIs for timeout and cpu_relax() for
tight loops instead of udelay().

cpu_relax() changes the priority everytime to low and will yield to
another thread.
Considering that we are checking the condition every microsecond does it make
some saving using cpu_relax().

cpu_relax() does not involve any priority changes or scheduling AFAICS.
Have a look at this thread:

http://www.spinics.net/lists/netdev/msg151699.html

Thanks. My bad. I meant yielding to another thread with in a space
of 1uS.

Regards
AnilKumar

-- 
Regards and Thanks,
Keerthy