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mmc: sdhci: Use Auto CMD Auto Select only when v4_mode is true

PATCH In review Jisheng Zhang 3 participants 3 messages Oct 15, 2020

Subsystems (2)
MMC, SD and SDIO Secure digital host controller interface (SDHCI) driver
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Jisheng Zhang

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#0 lore raw

PATCH v2 1/1 mmc: sdhci: Use Auto CMD Auto Select only when v4_mode is true

sdhci-of-dwcmshc meets an eMMC read performance regression with below command after commit 427b6514d095 ("mmc: sdhci: Add Auto CMD Auto Select support"):

dd if=/dev/mmcblk0 of=/dev/null bs=8192 count=100000

Before the commit, the above command gives 120MB/s After the commit, the above command gives 51.3 MB/s

So it looks like sdhci-of-dwcmshc expects Version 4 Mode for Auto CMD Auto Select. Fix the performance degradation by ensuring v4_mode is true to use Auto CMD Auto Select.

Fixes 427b6514d095 ("mmc: sdhci: Add Auto CMD Auto Select support")
Signed-off-by Jisheng Zhang <[email protected]>

---
Since v1:
- add the performance degradation on sdhci-of-dwcmshc explanation in commit msg
- add a comment in the code explaining we require Version 4 Mode because some controllers(e.g sdhci-of-dwcmshc) expect it that way.

 drivers/mmc/host/sdhci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
drivers/mmc/host/sdhci.c +4 -2
index 592a55a34b58..3561ae8a481a 100644
@@ -1384,9 +1384,11 @@ static inline void sdhci_auto_cmd_select(struct sdhci_host *host,
 	/*
 	 * In case of Version 4.10 or later, use of 'Auto CMD Auto
 	 * Select' is recommended rather than use of 'Auto CMD12
-	 * Enable' or 'Auto CMD23 Enable'.
+	 * Enable' or 'Auto CMD23 Enable'. We require Version 4 Mode
+	 * here because some controllers (e.g sdhci-of-dwmshc) expect it.
 	 */
-	if (host->version >= SDHCI_SPEC_410 && (use_cmd12 || use_cmd23)) {
+	if (host->version >= SDHCI_SPEC_410 && host->v4_mode &&
+	    (use_cmd12 || use_cmd23)) {
 		*mode |= SDHCI_TRNS_AUTO_SEL;
 
 		ctrl2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
Signature · 1 line
2.28.0
maintainer Acked-by on v2 1/1
#1 lore raw
Quoted 9 lines · Jisheng Zhang

sdhci-of-dwcmshc meets an eMMC read performance regression with below command after commit 427b6514d095 ("mmc: sdhci: Add Auto CMD Auto Select support"):

dd if=/dev/mmcblk0 of=/dev/null bs=8192 count=100000

Before the commit, the above command gives 120MB/s After the commit, the above command gives 51.3 MB/s

Quoted 6 lines

So it looks like sdhci-of-dwcmshc expects Version 4 Mode for Auto CMD Auto Select. Fix the performance degradation by ensuring v4_mode is true to use Auto CMD Auto Select.

Fixes 427b6514d095 ("mmc: sdhci: Add Auto CMD Auto Select support")
Signed-off-by Jisheng Zhang <[email protected]>
Acked-by Adrian Hunter <[email protected]>
Quoted 29 lines

---
Since v1:
- add the performance degradation on sdhci-of-dwcmshc explanation in commit msg
- add a comment in the code explaining we require Version 4 Mode because some controllers(e.g sdhci-of-dwcmshc) expect it that way.

 drivers/mmc/host/sdhci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
drivers/mmc/host/sdhci.c +4 -2
index 592a55a34b58..3561ae8a481a 100644
@@ -1384,9 +1384,11 @@ static inline void sdhci_auto_cmd_select(struct sdhci_host *host,
 	/*
 	 * In case of Version 4.10 or later, use of 'Auto CMD Auto
 	 * Select' is recommended rather than use of 'Auto CMD12
-	 * Enable' or 'Auto CMD23 Enable'.
+	 * Enable' or 'Auto CMD23 Enable'. We require Version 4 Mode
+	 * here because some controllers (e.g sdhci-of-dwmshc) expect it.
 	 */
-	if (host->version >= SDHCI_SPEC_410 && (use_cmd12 || use_cmd23)) {
+	if (host->version >= SDHCI_SPEC_410 && host->v4_mode &&
+	    (use_cmd12 || use_cmd23)) {
 		*mode |= SDHCI_TRNS_AUTO_SEL;
 
 		ctrl2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
#2 lore raw
In reply to Jisheng Zhang
Quoted 10 lines · Jisheng Zhang

sdhci-of-dwcmshc meets an eMMC read performance regression with below command after commit 427b6514d095 ("mmc: sdhci: Add Auto CMD Auto Select support"):

dd if=/dev/mmcblk0 of=/dev/null bs=8192 count=100000

Before the commit, the above command gives 120MB/s After the commit, the above command gives 51.3 MB/s

Quoted 6 lines

So it looks like sdhci-of-dwcmshc expects Version 4 Mode for Auto CMD Auto Select. Fix the performance degradation by ensuring v4_mode is true to use Auto CMD Auto Select.

Fixes 427b6514d095 ("mmc: sdhci: Add Auto CMD Auto Select support")
Signed-off-by Jisheng Zhang <[email protected]>

Applied for fixes and by adding a stable tag, thanks!

Kind regards
Uffe

Quoted 31 lines

---
Since v1:
- add the performance degradation on sdhci-of-dwcmshc explanation in commit msg
- add a comment in the code explaining we require Version 4 Mode because some controllers(e.g sdhci-of-dwcmshc) expect it that way.

 drivers/mmc/host/sdhci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
drivers/mmc/host/sdhci.c +4 -3
index 592a55a34b58..3561ae8a481a 100644
@@ -1384,9 +1384,11 @@ static inline void sdhci_auto_cmd_select(struct sdhci_host *host,
        /*
         * In case of Version 4.10 or later, use of 'Auto CMD Auto
         * Select' is recommended rather than use of 'Auto CMD12
-        * Enable' or 'Auto CMD23 Enable'.
+        * Enable' or 'Auto CMD23 Enable'. We require Version 4 Mode
+        * here because some controllers (e.g sdhci-of-dwmshc) expect it.
         */
-       if (host->version >= SDHCI_SPEC_410 && (use_cmd12 || use_cmd23)) {
+       if (host->version >= SDHCI_SPEC_410 && host->v4_mode &&
+           (use_cmd12 || use_cmd23)) {
                *mode |= SDHCI_TRNS_AUTO_SEL;
 
                ctrl2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
--

2.28.0