[PATCH] mci: imx-esdhc: send required clock pulses to card on init

[PATCH] mci: imx-esdhc: send required clock pulses to card on init

[Lucas Stach]

MMC cards need at least 74 clock pulses before any bus communication
can occur. The i.MX SDHC controller auto-gates the clock when inactive,
so if the SD enumeration is skipped for slots where we know that only a
MMC card can be present (which is possible since
b5289b742a89 "mmc: allow skipping SD card initialization") those
inititialization clock pulses won't be sent out, resulting in command
timeouts when trying to enumerate the card.

Luckily the eSDHC controller has a hardware feature to send out 80
clock pulses. This has been validated to be available by checking the
reference manual back to i.MX25.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/mci/imx-esdhc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/mci/imx-esdhc.c b/drivers/mci/imx-esdhc.c
index c4daa9d12136..db96a813971a 100644
--- a/drivers/mci/imx-esdhc.c
+++ b/drivers/mci/imx-esdhc.c
@@ -455,10 +455,13 @@ static void set_sysctl(struct mci_host *mci, u32 clock)
 	wait_on_timeout(10 * MSECOND,
 			esdhc_read32(regs + SDHCI_PRESENT_STATE) & PRSSTAT_SDSTB);
 
-	clk = SYSCTL_PEREN | SYSCTL_CKEN;
+	clk = SYSCTL_PEREN | SYSCTL_CKEN | SYSCTL_INITA;
 
 	esdhc_setbits32(regs + SDHCI_CLOCK_CONTROL__TIMEOUT_CONTROL__SOFTWARE_RESET,
 			clk);
+
+	wait_on_timeout(1 * MSECOND,
+			!(esdhc_read32(regs + SDHCI_CLOCK_CONTROL) & SYSCTL_INITA));
 }
 
 static void esdhc_set_ios(struct mci_host *mci, struct mci_ios *ios)
-- 
2.18.0


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Re: [PATCH] mci: imx-esdhc: send required clock pulses to card on init

[Sascha Hauer]

On Wed, Jul 25, 2018 at 11:57:28AM +0200, Lucas Stach wrote:
> MMC cards need at least 74 clock pulses before any bus communication
> can occur. The i.MX SDHC controller auto-gates the clock when inactive,
> so if the SD enumeration is skipped for slots where we know that only a
> MMC card can be present (which is possible since
> b5289b742a89 "mmc: allow skipping SD card initialization") those
> inititialization clock pulses won't be sent out, resulting in command
> timeouts when trying to enumerate the card.
> 
> Luckily the eSDHC controller has a hardware feature to send out 80
> clock pulses. This has been validated to be available by checking the
> reference manual back to i.MX25.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  drivers/mci/imx-esdhc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

Applied, thanks

Sascha

> 
> diff --git a/drivers/mci/imx-esdhc.c b/drivers/mci/imx-esdhc.c
> index c4daa9d12136..db96a813971a 100644
> --- a/drivers/mci/imx-esdhc.c
> +++ b/drivers/mci/imx-esdhc.c
> @@ -455,10 +455,13 @@ static void set_sysctl(struct mci_host *mci, u32 clock)
>  	wait_on_timeout(10 * MSECOND,
>  			esdhc_read32(regs + SDHCI_PRESENT_STATE) & PRSSTAT_SDSTB);
>  
> -	clk = SYSCTL_PEREN | SYSCTL_CKEN;
> +	clk = SYSCTL_PEREN | SYSCTL_CKEN | SYSCTL_INITA;
>  
>  	esdhc_setbits32(regs + SDHCI_CLOCK_CONTROL__TIMEOUT_CONTROL__SOFTWARE_RESET,
>  			clk);
> +
> +	wait_on_timeout(1 * MSECOND,
> +			!(esdhc_read32(regs + SDHCI_CLOCK_CONTROL) & SYSCTL_INITA));
>  }
>  
>  static void esdhc_set_ios(struct mci_host *mci, struct mci_ios *ios)
> -- 
> 2.18.0
> 
> 
> _______________________________________________
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> barebox@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/barebox
> 

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