On Tue, Nov 04, 2014 at 09:06:07AM +0100, Ulf Hansson wrote:
> On 7 October 2014 10:11, Ludovic Desroches <ludovic.desroches@xxxxxxxxx> wrote:
> > In programmable mode, if the clock frequency is too high, the divider
> > can be too small to meet the clock frequency requirement especially to
> > init the SD card. In this case, switch to the divided clock mode.
> >
> > Signed-off-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
> > ---
> >
> > Hi all,
> >
> > I would like to know if this patch can be accepted. Use case, I have a base
> > clock at 12 MHz, M is 40. So in programmable mode, using the greater divider,
> > minimum clock frequency will be higher than 400 KHz so it could cause issues to
> > init the card.
> >
> > Thanks for your feedback.
> >
> > Ludovic
>
> It would be nice if some of the senior sdhci developers could help out
> review patches likes this.
>
> It touches the core of sdhci, thus affecting many of the sdhci drivers.
>
> Anybody?
>
Ping, any feedback?
Regards
Ludovic
> Kind regards
> Uffe
>
> >
> > drivers/mmc/host/sdhci.c | 29 ++++++++++++++++++++---------
> > 1 file changed, 20 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index df0e7e1..70d4c18 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -1126,6 +1126,7 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
> > int real_div = div, clk_mul = 1;
> > u16 clk = 0;
> > unsigned long timeout;
> > + bool switch_base_clk = false;
> >
> > host->mmc->actual_clock = 0;
> >
> > @@ -1163,15 +1164,25 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
> > <= clock)
> > break;
> > }
> > - /*
> > - * Set Programmable Clock Mode in the Clock
> > - * Control register.
> > - */
> > - clk = SDHCI_PROG_CLOCK_MODE;
> > - real_div = div;
> > - clk_mul = host->clk_mul;
> > - div--;
> > - } else {
> > + if ((host->max_clk * host->clk_mul / div) <= clock) {
> > + /*
> > + * Set Programmable Clock Mode in the Clock
> > + * Control register.
> > + */
> > + clk = SDHCI_PROG_CLOCK_MODE;
> > + real_div = div;
> > + clk_mul = host->clk_mul;
> > + div--;
> > + } else {
> > + /*
> > + * Divisor can be too small to reach clock
> > + * speed requirement. Then use the base clock.
> > + */
> > + switch_base_clk = true;
> > + }
> > + }
> > +
> > + if (!host->clk_mul || switch_base_clk) {
> > /* Version 3.00 divisors must be a multiple of 2. */
> > if (host->max_clk <= clock)
> > div = 1;
> > --
> > 2.0.3
> >
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