[RFC] mmc: fsl_esdhc_imx: Use esdhc_soc_data flags to set host caps

[Adam Ford]

On Wed, Jan 6, 2021 at 7:06 PM Tim Harvey <tharvey at gateworks.com> wrote:
>
> On Tue, Jan 5, 2021 at 2:20 PM Adam Ford <aford173 at gmail.com> wrote:
> >
> > On Tue, Jan 5, 2021 at 4:07 PM Jaehoon Chung <jh80.chung at samsung.com> wrote:
> > >
> > > Hi Adam,
> > >
> > +CC: Tim Harvey,
> >
> > > On 12/31/20 2:39 AM, Adam Ford wrote:
> > > > The Linux driver automatically can detect and enable UHS, HS200, HS400
> > > > and HS400_ES automatically without extra flags being placed into the
> > > > device tree.
> > > >
> > > > Right now, for U-Boot to use UHS, HS200 or HS400, the extra flags are
> > > > needed.  Let's go through the esdhc_soc_data flags and enable the
> > > > host caps where applicable.
> > > >
> > > > Suggested-by: Fabio Estevam <festevam at gmail.com>
> > > > Signed-off-by: Adam Ford <aford173 at gmail.com>
> > > > ---
> > > > I am not an expert on the SD/MMC standards, but I used the Linux
> > > > driver as a model, and made the assumption that the USDHC flag needs
> > > > to be set in order to use the extra speeds.
> > >
> > > Looks good to me. If it can't parse property from device-tree, it needs to set host_caps as proper mode.
> > > Does it work fine about UHS mode? AFAIK, there was an issue about not detecting host capabilities.
> >
> > From the troubleshooting I've done, without this patch the host didn't
> > show it was capable of UHS, but with this patch, the card doesn't show
> > UHS, so I think there is something wrong still, but this at least gets
> > us past it being a host caps issue.
> > I was able to get it working with HS400ES.
> >
> > If you want me to hold off until we get UHS working, I can hold off.
> > I know Tim was having issues as well.
> >
> > I was able to confirm the UHS SDR104 works on the Renesas RZ/G2H board
> > that I have using the same care, so I think the issue may be unique to
> > the esdhc driver.
> >
>
> I'm all for this patch and getting rid of the custom u-boot props that
> were added to enable UHS.
>
> I don't think there is any need to wait as this patch does not cause
> any issue with microSD, just exposes something and if you hit the
> issue we are hitting with the microSD failing to acknowledge the
> voltage switch at least it falls back to legacy mode so it doesn't
> hurt to have this in place, esp given the benefit of enabling
> HS200/HS400/HS400ES. I could use some help understanding the microSD
> failing to acknowledge the voltage switch as I'm completely out of
> ideas.
>
> The IMX6 SDHC supports UHS as well but it isn't enabled by this patch
> - have you tried enabling UHS for IMX6?

I have an i.MX6Q laying around somewhere, but I haven't tested it.  I
would expect the patch to enable the settings based on the host caps.
If they're not set in the host flag, I think a separate patch would be
appropriate to update the i.MX6 flags regardless of whether or not
this patch gets accepted. There are so many variants of i.MX6, I am
reluctant to do it for fear of breaking something.

adam
>
> Best regards,
>
> Tim