From: Sascha Hauer <s.hauer@pengutronix.de>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH] mci: imx-esdhc: send required clock pulses to card on init
Date: Wed, 8 Aug 2018 08:35:44 +0200 [thread overview]
Message-ID: <20180808063544.poxqd77tcskhzgaa@pengutronix.de> (raw)
In-Reply-To: <20180725095728.16369-1-l.stach@pengutronix.de>
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
>
>
> _______________________________________________
> barebox mailing list
> barebox@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/barebox
>
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prev parent reply other threads:[~2018-08-08 6:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-25 9:57 Lucas Stach
2018-08-08 6:35 ` Sascha Hauer [this message]
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