On Wed, 12 Jun 2024 at 17:48, Conor Dooley <conor@xxxxxxxxxx> wrote: > > From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx> > > Some controllers may not be able to reach a bus clock as low as 400 KHz > due to a lack of sufficient divisors. In these cases, the SD card slot > becomes non-functional as Linux continuously attempts to set the bus > clock to 400 KHz. If the controller is incapable of getting that low, > set its minimum frequency instead. While this may eliminate some SD > cards, it allows those capable of operating at the controller's minimum > frequency to be used. > > Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx> Looks reasonable to me. I assume you intend to send a non-RFC for this, that I can pick up? Kind regards Uffe > --- > drivers/mmc/host/mmc_spi.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c > index 09d7a6a0dc1a..c9caa1ece7ef 100644 > --- a/drivers/mmc/host/mmc_spi.c > +++ b/drivers/mmc/host/mmc_spi.c > @@ -1208,7 +1208,10 @@ static int mmc_spi_probe(struct spi_device *spi) > * that's the only reason not to use a few MHz for f_min (until > * the upper layer reads the target frequency from the CSD). > */ > - mmc->f_min = 400000; > + if (spi->controller->min_speed_hz > 400000) > + dev_warn(&spi->dev,"Controller unable to reduce bus clock to 400 KHz\n"); > + > + mmc->f_min = max(spi->controller->min_speed_hz, 400000); > mmc->f_max = spi->max_speed_hz; > > host = mmc_priv(mmc); > -- > 2.43.0 >
