mmc: use usleep_range() in mmc_delay()

PATCH In review Dmitry Antipov 3 participants 7 messages Dec 21, 2011 – Jan 13, 2012 MMC, SD and SDIO

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Dmitry Antipov

author

2011-12-21 06:55 UTC #0 lore raw

PATCH 1/1 mmc: use usleep_range() in mmc_delay()

From f447d78db65c6675e69466e8ed08364ff065ac08 Mon Sep 17 00:00:00 2001
From: Dmitry Antipov <[email protected]>
Date: Wed, 21 Dec 2011 10:51:03 +0400
Subject: [PATCH] mmc: use usleep_range() in mmc_delay()

---
 drivers/mmc/core/core.h |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)

drivers/mmc/core/core.h +2 -6

index 14664f1..a77851e 100644
@@ -47,12 +47,8 @@ void mmc_power_off(struct mmc_host *host);
 
 static inline void mmc_delay(unsigned int ms)
 {
-	if (ms < 1000 / HZ) {
-		cond_resched();
-		mdelay(ms);
-	} else {
-		msleep(ms);
-	}
+	unsigned long us = ms * USEC_PER_MSEC;
+	usleep_range(us, us + 1000);
 }
 
 void mmc_rescan(struct work_struct *work);

Signature · 1 line

1.7.7.4

Sujit Reddy Thumma

2011-12-21 11:25 UTC #1 lore raw

Quoted 15 lines · Dmitry Antipov

From f447d78db65c6675e69466e8ed08364ff065ac08 Mon Sep 17 00:00:00 2001
From: Dmitry Antipov <[email protected]>
Date: Wed, 21 Dec 2011 10:51:03 +0400
Subject: [PATCH] mmc: use usleep_range() in mmc_delay()
---
drivers/mmc/core/core.h | 8 ++------
1 files changed, 2 insertions(+), 6 deletions(-)
drivers/mmc/core/core.h +0 -0
index 14664f1..a77851e 100644
@@ -47,12 +47,8 @@ void mmc_power_off(struct mmc_host *host);
 

drivers/mmc/core/core.h void mmc_power_off(struct mmc_host *host); · line 51

Quoted 10 lines

drivers/mmc/core/core.h +2 -6

 static inline void mmc_delay(unsigned int ms)
 {
- if (ms < 1000 / HZ) {
- cond_resched();
- mdelay(ms);
- } else {
- msleep(ms);
- }
+ unsigned long us = ms * USEC_PER_MSEC;
+ usleep_range(us, us + 1000);

I have posted similar patch some time back. http://comments.gmane.org/gmane.linux.ports.arm.msm/2119.

Would you like to comment on that?

Thanks,
Sujit

Quoted 3 lines

drivers/mmc/core/core.h +0 -0

 }
 
 void mmc_rescan(struct work_struct *work);

Dmitry Antipov

author

2011-12-21 13:04 UTC #2 lore raw

Quoted 4 lines · Sujit Reddy Thumma

I have posted similar patch some time back.
http://comments.gmane.org/gmane.linux.ports.arm.msm/2119.
Would you like to comment on that?

- I believe we should forget about jiffies, HZ and other similar obsolete timekeeping stuff;

- I have no ideas where did you get 'most typical' 20 ms. MMC subsystem uses mmc_delay() with two compile-time fixed values 1 and 10 ms, with the only exception of card-dependent sleep/awake timeout. I was unable to find a table with typical values, but it's rounded up to >= 1 ms anyway.

Dmitry

Sujit Reddy Thumma

2011-12-27 04:40 UTC #3 lore raw

Hi Antipov,

Sorry for the delayed response. Please find some comments below:

Quoted 10 lines · Dmitry Antipov

Quoted 4 lines · Sujit Reddy Thumma
I have posted similar patch some time back.
http://comments.gmane.org/gmane.linux.ports.arm.msm/2119.
Would you like to comment on that?
- I believe we should forget about jiffies, HZ and other similar obsolete timekeeping stuff;

Quoted 6 lines

- I have no ideas where did you get 'most typical' 20 ms. MMC subsystem uses
mmc_delay() with two compile-time fixed values 1 and 10 ms, with the only exception of card-dependent sleep/awake timeout. I was unable to find a table
with typical values, but it's rounded up to >= 1 ms anyway.

The main aim of my patch was to fix mmc_delay() to give accurate delay.
You might want to refer to Documentation/timers/timers-howto.txt (Section: SLEEPING FOR ~USECS OR SMALL MSECS) to know why usleep_range() must be used instead of msleep for delays less than 20ms (or more accurately two jiffies, since in HZ=100 systems this comes to 20ms).

Also, in the documentation it is suggested that for delays greater than 10ms+ use msleep(). Although MMC subsystem doesn't use mmc_delay() for greater than 10ms today but I guess we should keep it for future purpose and just not have only usleep_range() as your patch did.

Quoted 2 lines

Dmitry

Aaro Koskinen

2012-01-13 13:24 UTC #4 lore raw

In reply to Dmitry Antipov

Hi,

Quoted 6 lines · Dmitry Antipov

From f447d78db65c6675e69466e8ed08364ff065ac08 Mon Sep 17 00:00:00 2001
From: Dmitry Antipov <[email protected]>
Date: Wed, 21 Dec 2011 10:51:03 +0400
Subject: [PATCH] mmc: use usleep_range() in mmc_delay()
---

Shouldn't you add a proper patch description and a signed-off-by line?

Quoted 10 lines

drivers/mmc/core/core.h | 8 ++------

1 files changed, 2 insertions(+), 6 deletions(-)

drivers/mmc/core/core.h +0 -0

index 14664f1..a77851e 100644
@@ -47,12 +47,8 @@ void mmc_power_off(struct mmc_host *host);
 
 static inline void mmc_delay(unsigned int ms)

drivers/mmc/core/core.h void mmc_power_off(struct mmc_host *host); · line 52

Quoted 10 lines

drivers/mmc/core/core.h +2 -6

 {
-	if (ms < 1000 / HZ) {
-		cond_resched();
-		mdelay(ms);
-	} else {
-		msleep(ms);
-	}
+	unsigned long us = ms * USEC_PER_MSEC;
+	usleep_range(us, us + 1000);
 }

Anyway, I think the change is good. On systems with multiple MMC devices the boot/probe can spend 100-200 ms alone just doing busylooping delays. I think e.g. in mmc_rescan() the code uses frequently mmc_delay(10).

Quoted 3 lines

drivers/mmc/core/core.h +0 -0
 void mmc_rescan(struct work_struct *work);
Signature · 1 line
1.7.7.4

Dmitry Antipov

author

2012-01-13 13:50 UTC #5 lore raw

Quoted 3 lines · Aaro Koskinen

Anyway, I think the change is good. On systems with multiple MMC devices the boot/probe can spend 100-200 ms alone just doing busylooping delays. I think e.g. in mmc_rescan() the code uses frequently mmc_delay(10).

I'm worrying about this:

mmc_delay(DIV_ROUND_UP(card->ext_csd.sa_timeout, 10000))

since I have no ideas about typical values for this timeout. If it may be too small (<=10 us), using usleep_range() makes no sense.

Dmitry

Aaro Koskinen

2012-01-13 14:55 UTC #6 lore raw

Hi,

Quoted 6 lines · Dmitry Antipov

Quoted 3 lines · Aaro Koskinen
Anyway, I think the change is good. On systems with multiple MMC devices the boot/probe can spend 100-200 ms alone just doing busylooping delays. I think e.g. in mmc_rescan() the code uses frequently mmc_delay(10).

Quoted 6 lines

I'm worrying about this:
mmc_delay(DIV_ROUND_UP(card->ext_csd.sa_timeout, 10000))
since I have no ideas about typical values for this timeout. If it may be too small (<=10 us), using usleep_range() makes no sense.

Hmm, but the code above is rounding it up to at least 1 ms?