| Message ID | 20240612-dense-resample-563f07c30185@spud |
|---|---|
| State | New |
| Headers | show |
| Series | mmc-spi - support controllers incapable of getting as low as 400KHz | expand |
On Wed, 12 Jun 2024 at 17:48, Conor Dooley <conor@kernel.org> wrote: > > From: Conor Dooley <conor.dooley@microchip.com> > > 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@microchip.com> 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 >
On Thu, Jun 20, 2024 at 02:50:15PM +0200, Ulf Hansson wrote: > On Wed, 12 Jun 2024 at 17:48, Conor Dooley <conor@kernel.org> wrote: > > > > From: Conor Dooley <conor.dooley@microchip.com> > > > > 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@microchip.com> > > Looks reasonable to me. I assume you intend to send a non-RFC for > this, that I can pick up? I do intend doing that. How soon depends on whether or not you are willing to take it on its own, or require it to come in a series with the spi driver changes. Thanks, Conor.
On Thu, 20 Jun 2024 at 16:12, Conor Dooley <conor@kernel.org> wrote: > > On Thu, Jun 20, 2024 at 02:50:15PM +0200, Ulf Hansson wrote: > > On Wed, 12 Jun 2024 at 17:48, Conor Dooley <conor@kernel.org> wrote: > > > > > > From: Conor Dooley <conor.dooley@microchip.com> > > > > > > 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@microchip.com> > > > > Looks reasonable to me. I assume you intend to send a non-RFC for > > this, that I can pick up? > > I do intend doing that. How soon depends on whether or not you are > willing to take it on its own, or require it to come in a series with > the spi driver changes. I can pick it separately, if that makes sense to you. Kind regards Uffe
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);