Re: [PATCH 1/3] mmc: sdhci-cadence: enable v4_mode to fix ADMA 64-bit addressing

[Ulf Hansson]

On Thu, 29 Aug 2019 at 16:04, Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> wrote:
>
> Hi Ulf,
>
> On Thu, Aug 29, 2019 at 10:27 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> >
> > On Thu, 29 Aug 2019 at 14:05, Masahiro Yamada
> > <yamada.masahiro@xxxxxxxxxxxxx> wrote:
> > >
> > > On Thu, Aug 29, 2019 at 8:48 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> > > >
> > > > On Thu, 29 Aug 2019 at 12:49, Masahiro Yamada
> > > > <yamada.masahiro@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > The IP datasheet says this controller is compatible with SD Host
> > > > > Specification Version v4.00.
> > > > >
> > > > > As it turned out, the ADMA of this IP does not work with 64-bit mode
> > > > > when it is in the Version 3.00 compatible mode; it understands the
> > > > > old 64-bit descriptor table (as defined in SDHCI v2), but the ADMA
> > > > > System Address Register (SDHCI_ADMA_ADDRESS) cannot point to the
> > > > > 64-bit address.
> > > > >
> > > > > I noticed this issue only after commit bd2e75633c80 ("dma-contiguous:
> > > > > use fallback alloc_pages for single pages"). Prior to that commit,
> > > > > dma_set_mask_and_coherent() returned the dma address that fits in
> > > > > 32-bit range, at least for the default arm64 configuration
> > > > > (arch/arm64/configs/defconfig). Now the host->adma_addr exceeds the
> > > > > 32-bit limit, causing the real problem for the Socionext SoCs.
> > > > > (As a side-note, I was also able to reproduce the issue for older
> > > > > kernels by turning off CONFIG_DMA_CMA.)
> > > > >
> > > > > Call sdhci_enable_v4_mode() to fix this.
> > > > >
> > > > > I think it is better to back-port this, but only possible for v4.20+.
> > > > >
> > > > > When this driver was merged (v4.10), the v4 mode support did not exist.
> > > > > It was added by commit b3f80b434f72 ("mmc: sdhci: Add sd host v4 mode")
> > > > > i.e. v4.20.
> > > > >
> > > > > Cc: <stable@xxxxxxxxxxxxxxx> # v4.20+
> > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> > > >
> > > > Applied for fixes, by adding below tag, thanks!
> > > >
> > > > Fixes: b3f80b434f72 ("mmc: sdhci: Add sd host v4 mode")
> > >
> > > This is not a bug commit.
> >
> > Right, but it can't be applied before this commit, hence why I added
> > it. Not sure that it matters, but I can remove the tag if you
> > insists!?
>
> I hesitate to add Fixes to the commit that
> did nothing wrong.
>
>
> I added "Cc: <stable@xxxxxxxxxxxxxxx> # v4.20+"
> so this is enough for the stable kernel maintainers.

Yes, I drop the fixes tag. But as I said, I don't think it's a big deal.

Kind regards
Uffe