[PATCH] sdhci: add ops to force delay in operations due to silicon issues

* [PATCH] sdhci: add ops to force delay in operations due to silicon issues
@ 2011-02-14  7:21 Philip Rakity
  0 siblings, 0 replies; 3+ messages in thread
From: Philip Rakity @ 2011-02-14  7:21 UTC (permalink / raw)
  To: linux-mmc; +Cc: Mark Brown


PXA168 controller needs at least 8 clocks before it can start the
next transaction.  When the bus speed is slow the CPU can get back
to the controller before the 8 clocks causing SD CRC errors.

Add a new host->op to call into platform specific code to delay
the operation until the time has expired

Signed-off-by: Philip Rakity <prakity@marvell.com>
---
 drivers/mmc/host/sdhci.c |    8 ++++++++
 drivers/mmc/host/sdhci.h |    1 +
 2 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 8bd3e37..fb084c4 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -925,6 +925,14 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
 		mdelay(1);
 	}
 
+	/*
+	 * we cannot talk to controller for 8 bus cycles according to sdio spec
+	 * at lowest speed this is 100,000 HZ per cycle or 800,000 cycles
+	 * which is quite a LONG TIME on a fast cpu -- so delay if needed
+	 */
+	if (host->ops->platform_specific_delay)
+		host->ops->platform_specific_delay(host);
+
 	mod_timer(&host->timer, jiffies + 10 * HZ);
 
 	host->cmd = cmd;
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index abb1170..d2fe13b 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -245,6 +245,7 @@ struct sdhci_ops {
 	unsigned int	(*get_f_max_clock)(struct sdhci_host *host);
 	unsigned int    (*set_signaling_voltage)(struct sdhci_host *host,
 				unsigned int ddr);
+	void	(*platform_specific_delay)(struct sdhci_host *host);
 };
 
 #ifdef CONFIG_MMC_SDHCI_IO_ACCESSORS
-- 
1.7.0.4



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