diff mbox

[v6,03/12] mmc: mmci: Add enough delay between writes to CMD register.

Message ID 1401700137-11547-1-git-send-email-srinivas.kandagatla@linaro.org
State New
Headers show

Commit Message

Srinivas Kandagatla June 2, 2014, 9:08 a.m. UTC 
From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

On Qcom SD Card controller POWER, CLKCTRL, DATACTRL and COMMAND registers
should be updated in MCLK domain, and writes to these registers must be
separated by three MCLK cycles. This resitriction is not applicable for
other registers. Any subsequent writes to these register will be ignored
until 3 MCLK have passed.

One usec delay between two CMD register writes is not sufficient in the
card identification phase where the CCLK is very low. This patch replaces
a static 1 usec delay to use mmci_reg_delay function which can provide
correct delay depending on the cclk frequency.

Without this patch the card is not detected.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
 drivers/mmc/host/mmci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Linus Walleij June 11, 2014, 12:46 p.m. UTC | #1 
On Mon, Jun 2, 2014 at 11:08 AM,  <srinivas.kandagatla@linaro.org> wrote:

> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>
> On Qcom SD Card controller POWER, CLKCTRL, DATACTRL and COMMAND registers
> should be updated in MCLK domain, and writes to these registers must be
> separated by three MCLK cycles. This resitriction is not applicable for
> other registers. Any subsequent writes to these register will be ignored
> until 3 MCLK have passed.
>
> One usec delay between two CMD register writes is not sufficient in the
> card identification phase where the CCLK is very low. This patch replaces
> a static 1 usec delay to use mmci_reg_delay function which can provide
> correct delay depending on the cclk frequency.
>
> Without this patch the card is not detected.
>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij
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diff mbox

Patch

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index a38e714..ed20bf5 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -810,7 +810,7 @@  mmci_start_command(struct mmci_host *host, struct mmc_command *cmd, u32 c)
 
 	if (readl(base + MMCICOMMAND) & MCI_CPSM_ENABLE) {
 		writel(0, base + MMCICOMMAND);
-		udelay(1);
+		mmci_reg_delay(host);
 	}
 
 	c |= cmd->opcode | MCI_CPSM_ENABLE;