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@xxxxxxxxxxx>
---
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 6486009..ff9d5f0 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -922,6 +922,14 @@ 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 a8c43c9..91749dc 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -225,6 +225,7 @@ struct sdhci_ops {
void (*platform_reset_enter)(struct sdhci_host *host, u8 mask);
void (*platform_reset_exit)(struct sdhci_host *host, u8 mask);
unsigned int (*get_f_max_clock)(struct sdhci_host *host);
+ void (*platform_specific_delay)(struct sdhci_host *host);
};
#ifdef CONFIG_MMC_SDHCI_IO_ACCESSORS
--
1.7.0.4
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
