linux-kernel - [PATCH 9/7] mmc_spi: speedup for slow cards

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Date:	Thu, 12 Mar 2009 15:45:15 +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 9/7] mmc_spi: speedup for slow cards

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

o Speedup for slow cards by transfering more data at once.  

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

---

diff -uprN 2_6_29_rc7_patch8_documentation/drivers/mmc/host/mmc_spi.c 2_6_29_rc7_patch9_speedup/drivers/mmc/host/mmc_spi.c
--- 2_6_29_rc7_patch8_documentation/drivers/mmc/host/mmc_spi.c	2009-03-12 10:54:24.000000000 +0100
+++ 2_6_29_rc7_patch9_speedup/drivers/mmc/host/mmc_spi.c	2009-03-12 14:35:27.000000000 +0100
@@ -111,6 +111,14 @@
  */
 #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
 
 /****************************************************************************/
 
@@ -1381,6 +1389,10 @@ 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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