Re: [PATCH RFC 4/4] mmc: sdhci-of-dwcmshc: Add support for T-Head TH1520

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On Tue, Jul 25, 2023 at 11:03:44PM +0800, Jisheng Zhang wrote:
> On Mon, Jul 24, 2023 at 05:59:18PM -0700, Drew Fustini wrote:
> > Add basic support for the T-Head TH1520 SoC mmc controller. The new
> > compatible "thead,th1520-dwcmshc" enables basic support by:
> Hi Drew,
> > 
> >  - Enabling v4 mode to properly communicate with the mmc device
> >  - Setting quirk to disable ADMA
> >  - Setting flag to disable SDMA and force PIO mode
> >  - Turing .reset op into a no-op as the driver does not yet know how to
> >    configure the phy. Rely on the vendor u-boot to have configured the
> >    phy and do not reset the controller in Linux.
> The last three itmes are not acceptable. The controller supports ADMA
> well, can you plz bring in the phy driver? We can't rely on bootloader to
> configure phy.

Yes, that makes sense that this is not acceptable. The T-Head vendor
kernel seems to contain all the necessary information needed to add the
phy configuration to sdhci-of-dwcmshc.

The shipping kernel for the BeagleV Ahead [1] is based on the T-Head SDK
releases. I looked at changes to drivers/mmc and found that key changes
are from Linux_SDK_V0.9.5 [2] and Linux_SDK_V1.0.2 [3].

That kernel contains drivers/mmc/host/sdhci-of-dwcmshc.h [4] which seems
to define information about the phy registers. The version of
drivers/mmc/host/sdhci-of-dwcmshc.h in that kernel defines several
functions for the phy config and controller reset:


I'll look into adapting that code into the upstream sdhci-of-dwcmshc.



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