Re: [PATCH] mmc: sdhci-iproc: Add ACPI bindings for the rpi4

[Jeremy Linton]

Hi,

On 1/11/21 6:23 AM, Stefan Wahren wrote:
> Hi,
>
> Am 11.01.21 um 04:39 schrieb Jeremy Linton:
> > Hi,
> >
> > On 1/9/21 5:07 AM, Stefan Wahren wrote:
> > > Hi Jeremy,
> > >
> > > +add Nicolas
> > >
> > > Am 08.01.21 um 22:13 schrieb Jeremy Linton:
> > > > The rpi4 has a Arasan controller it carries over
> > > > from the rpi3, and a newer eMMC2 controller.
> > > > Because of a couple "quirks" it seems wiser to bind
> > > > these controllers to the same driver that DT is using
> > > > on this platform rather than the generic sdhci_acpi
> > > > driver with PNP0D40.
> > > >
> > > > So, we use BCM2847 for the older Arasan and BRCME88C
> > > > for the newer eMMC2.
> > > >
> > > > With this change linux is capable of utilizing the
> > > > SD card slot, and the wifi on this platform
> > > > with linux.
> > > >
> > > > Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> > > > ---
> > > >    drivers/mmc/host/sdhci-iproc.c | 14 ++++++++++++++
> > > >    1 file changed, 14 insertions(+)
> > > >
> > > > diff --git a/drivers/mmc/host/sdhci-iproc.c
> > > > b/drivers/mmc/host/sdhci-iproc.c
> > > > index c9434b461aab..f79d97b41805 100644
> > > > --- a/drivers/mmc/host/sdhci-iproc.c
> > > > +++ b/drivers/mmc/host/sdhci-iproc.c
> > > > @@ -250,6 +250,14 @@ static const struct sdhci_pltfm_data
> > > > sdhci_bcm2835_pltfm_data = {
> > > >        .ops = &sdhci_iproc_32only_ops,
> > > >    };
> > > >    +static const struct sdhci_pltfm_data sdhci_bcm_arasan_data = {
> > > > +    .quirks = SDHCI_QUIRK_BROKEN_CARD_DETECTION |
> > > > +          SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK |
> > > > +          SDHCI_QUIRK_NO_HISPD_BIT,
> > > > +    .quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN,
> > > > +    .ops = &sdhci_iproc_32only_ops,
> > > > +};
> >
> > First, thanks for taking a look at this!
> >
> >
> > > Why do we need an almost exact copy of bcm2835_data which works fine for
> > > all Raspberry Pi boards?
> >
> > The short answer to the remainder of this email is that i'm trying to
> > continue supporting existing OSs (windows) using the ACPI tables on
> > the rpi3/rpi4 while adding rpi4+Linux support.
> >
> > An even shorter answer is they don't work because ACPI doesn't provide
> > the same clock/attributes/etc controls that exist with DT.
> >
> > So, what happened here is that I got this controller "working" with
> > the generic PNP0D40 sdhci_acpi driver. I managed this only by
> > controlling the sdhci_caps/masks in the firmware. In theory this
> > minimizes the amount of work needed on the other OS which are booting
> > on the same ACPI tables (*bsds). They should only need to quirk the
> > bcm/arasan specific functionality, rather than some of the quirking
> > which change the caps behavior. But because we don't know which if any
> > of the older rpi/arasan quirks are still needed the safest solution is
> > to use the _iproc driver and just drop the quirk flags known to be
> > worked around by the firmware caps override.
>
> okay, thanks for the explanation. I was also confused by bcm_arasan,
> because there is already an Arasan specific sdhci driver. But now it's
> clear to me.
>
> Could you please add a short comment (above sdhci_bcm_arasan_data) why
> we cannot use bcm2835_data?

Sure.

> Btw the subject isn't complete. The patch is also related to the rpi3.

Only via the historical ACPI tables. There isn't any attempt to get 
ACPI+Linux working on the rpi3. Its to far away from BSA. For starters 
it doesn't have a GIC. So while one could bind this driver on the rpi3, 
that would require being able to boot Linux on the rpi3 in ACPI mode.

Thanks again!



> Best regards
> Stefan