linux-kernel - [PATCH] mmc_spi: fail gracefully if host or card do not support the switch command

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Date:	Thu, 11 Jun 2009 16:13:27 +0100
From:	Wolfgang Mües <wolfgang.mues@...rswald.de>
To:	Pierre Ossman <drzeus@...eus.cx>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Matt Fleming" <matt@...sole-pimps.org>,
	"David Brownell" <dbrownell@...rs.sourceforge.net>,
	"Mike Frysinger" <vapier.adi@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mmc_spi: fail gracefully if host or card do not support the switch command

From: Wolfgang Muees <wolfgang.mues@...rswald.de>

The switch command (typically speed switching from 25 to 50 MHz clock)
can be rejected by _both_ the host controller/driver and by the card.
Elder revisions of the SD card do not support speed switching.
Fail gracefully if the reject is comming from the card.

Signed-off-by: Wolfgang Muees <wolfgang.mues@...rswald.de>

---
diff -uprN 2_6_29_rc7_patch_retries/drivers/mmc/core/mmc.c 2_6_29_rc7_patch_switch/drivers/mmc/core/mmc.c
--- 2_6_29_rc7_patch_retries/drivers/mmc/core/mmc.c	2009-03-04 02:05:22.000000000 +0100
+++ 2_6_29_rc7_patch_switch/drivers/mmc/core/mmc.c	2009-06-11 17:09:48.000000000 +0200
@@ -180,11 +180,11 @@ static int mmc_read_ext_csd(struct mmc_c
 
 	err = mmc_send_ext_csd(card, ext_csd);
 	if (err) {
-		/*
-		 * We all hosts that cannot perform the command
-		 * to fail more gracefully
-		 */
-		if (err != -EINVAL)
+		/* If the host or the card can't do the switch,
+		 * fail more gracefully. */
+		if ((err != -EINVAL)
+		 && (err != -ENOSYS)
+		 && (err != -EFAULT))
 			goto out;
 
 		/*
diff -uprN 2_6_29_rc7_patch_retries/drivers/mmc/core/sd.c 2_6_29_rc7_patch_switch/drivers/mmc/core/sd.c
--- 2_6_29_rc7_patch_retries/drivers/mmc/core/sd.c	2009-04-07 15:39:22.000000000 +0200
+++ 2_6_29_rc7_patch_switch/drivers/mmc/core/sd.c	2009-06-11 17:09:43.000000000 +0200
@@ -210,11 +210,11 @@ static int mmc_read_switch(struct mmc_ca
 
 	err = mmc_sd_switch(card, 0, 0, 1, status);
 	if (err) {
-		/*
-		 * We all hosts that cannot perform the command
-		 * to fail more gracefully
-		 */
-		if (err != -EINVAL)
+		/* If the host or the card can't do the switch,
+		 * fail more gracefully. */
+		if ((err != -EINVAL)
+		 && (err != -ENOSYS)
+		 && (err != -EFAULT))
 			goto out;
 
 		printk(KERN_WARNING "%s: problem reading switch "
---
regards

i. A. Wolfgang Mües
-- 
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Hardware Development
Telefon: +49 (0)5306 9219 0
Telefax: +49 (0)5306 9219 94 
E-Mail: Wolfgang.Mues@...rswald.de
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