linux-kernel - [PATCH 2/7] mmc_spi: wait more bytes for card response

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Date:	Wed, 11 Mar 2009 14:17:43 +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 2/7] mmc_spi: wait more bytes for card response

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

o some cards are slower than the standard allows and need more
  time to respond to a command. Max. observed number of bytes
  was 12.

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

---
This is one of a line of patches to enhance the usability of
the mmc spi host port driver from "don't work with most SD cards"
to "work with nearly all SD cards" (including those ugly cards
with non-byte-aligned responses).

diff -uprN 2_6_29_rc7_patch1_spi_mode_3/drivers/mmc/host/mmc_spi.c 2_6_29_rc7_patch2_wait_16bytes_response/drivers/mmc/host/mmc_spi.c
--- 2_6_29_rc7_patch1_spi_mode_3/drivers/mmc/host/mmc_spi.c	2009-03-11 12:58:47.000000000 +0100
+++ 2_6_29_rc7_patch2_wait_16bytes_response/drivers/mmc/host/mmc_spi.c	2009-03-11 13:00:06.000000000 +0100
@@ -279,8 +279,11 @@ static int mmc_spi_response_get(struct m
 		 * so it can always DMA directly into the target buffer.
 		 * It'd probably be better to memcpy() the first chunk and
 		 * avoid extra i/o calls...
+		 *
+		 * Note we check for more than 8 bytes, because in practice,
+		 * some SD cards are slow...
 		 */
-		for (i = 2; i < 9; i++) {
+		for (i = 2; i < 16; i++) {
 			value = mmc_spi_readbytes(host, 1);
 			if (value < 0)
 				goto done;

---
regards

i. A. Wolfgang Mües
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