linux-kernel - [PATCH] mmc_spi: speedup for slow cards, less wear-out

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Date:	Wed, 8 Apr 2009 10:14:07 +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: speedup for slow cards, less wear-out

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

o Speedup for slow cards by transfering more data at once.
  This patch also reduces the amount of wear-out of the flash
  blocks because fewer partial blocks are written.  

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

---

diff -uprN 2_6_29_rc7_patch1253467/drivers/mmc/host/mmc_spi.c 2_6_29_rc7_patch_wearout_speedup/drivers/mmc/host/mmc_spi.c
--- 2_6_29_rc7_patch1253467/drivers/mmc/host/mmc_spi.c	2009-04-07 17:19:21.000000000 +0200
+++ 2_6_29_rc7_patch_wearout_speedup/drivers/mmc/host/mmc_spi.c	2009-04-08 11:11:20.000000000 +0200
@@ -97,6 +97,14 @@
  */
 #define r1b_timeout		(HZ * 3)
 
+/* One of the critical speed parameters is the amount of data which may
+ * be transfered in one command. If this value is too low, the SD card
+ * controller has to do multiple partial block writes (argggh!). With
+ * today (2008) SD cards there is little speed gain if we transfer more
+ * than 64 KBytes at a time. So use this value until there is any indication
+ * that we should do more here.
+ */
+#define MMC_SPI_BLOCKSATONCE	128
 
 /****************************************************************************/
 
@@ -1366,6 +1374,10 @@ static int mmc_spi_probe(struct spi_devi
 
 	mmc->ops = &mmc_spi_ops;
 	mmc->max_blk_size = MMC_SPI_BLOCKSIZE;
+	mmc->max_hw_segs = MMC_SPI_BLOCKSATONCE;
+	mmc->max_phys_segs = MMC_SPI_BLOCKSATONCE;
+	mmc->max_req_size = MMC_SPI_BLOCKSATONCE * MMC_SPI_BLOCKSIZE;
+	mmc->max_blk_count = MMC_SPI_BLOCKSATONCE;
 
 	mmc->caps = MMC_CAP_SPI;
 
---
regards

i. A. Wolfgang Mües
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