[U-Boot] [PATCH] mmc: sdhci: Fix the SD clock stop sequence

[Yang, Wenyou]

Hi Pantelis,

> -----Original Message-----
> From: Pantelis Antoniou [mailto:panto at antoniou-consulting.com]
> Sent: 2015年9月21日 23:36
> To: Yang, Wenyou
> Cc: U-Boot Mailing List
> Subject: Re: [PATCH] mmc: sdhci: Fix the SD clock stop sequence
> 
> Hi Wenyou,
> 
> > On Sep 16, 2015, at 11:22 , Wenyou Yang <wenyou.yang at atmel.com> wrote:
> >
> > According to the SDHC specification, stopping the SD Clock is by
> > setting the SD Clock Enable bit in the Clock Control register at 0,
> > instead of setting all bits at 0.
> >
> > Before stopping the SD clock, we need to make sure all SD transactions
> > to complete, so add checking the CMD and DAT bits in the Presen State
> > register, before stopping the SD clock.
> >
> > Signed-off-by: Wenyou Yang <wenyou.yang at atmel.com>
> > ---
> >
> > drivers/mmc/sdhci.c |   10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mmc/sdhci.c b/drivers/mmc/sdhci.c index
> > d89e302..f02db4e 100644
> > --- a/drivers/mmc/sdhci.c
> > +++ b/drivers/mmc/sdhci.c
> > @@ -286,9 +286,15 @@ static int sdhci_send_command(struct mmc *mmc,
> > struct mmc_cmd *cmd, static int sdhci_set_clock(struct mmc *mmc,
> > unsigned int clock) {
> > 	struct sdhci_host *host = mmc->priv;
> > -	unsigned int div, clk, timeout;
> > +	unsigned int div, clk, timeout, reg;
> >
> > -	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> > +	while (sdhci_readl(host, SDHCI_PRESENT_STATE) &
> > +			   (SDHCI_CMD_INHIBIT | SDHCI_DATA_INHIBIT))
> > +		;
> > +
> 
> Put a timeout here in case something is broken.
The timeout is added in the version 2.


> 
> > +	reg = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > +	reg &= ~SDHCI_CLOCK_CARD_EN;
> > +	sdhci_writew(host, reg, SDHCI_CLOCK_CONTROL);
> >
> > 	if (clock == 0)
> > 		return 0;
> > --
> > 1.7.9.5
> >
> 
> Regards
> 
> — Pantelis

Best Regards,
Wenyou Yang