Re: [PATCH] arm64: dts: qcom: sc7180: Mark SCM as dma-coherent for trogdor

[Doug Anderson]

Hi,

On Thu, Jun 15, 2023 at 2:59 PM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote:
>
> Trogdor devices use firmware backed by TF-A instead of Qualcomm's
> normal TZ. On TF-A we end up mapping memory as cachable. Specifically,
> you can see in Trogdor's TF-A code [1] in qti_sip_mem_assign() that we
> call qti_mmap_add_dynamic_region() with MT_RO_DATA. This translates
> down to MT_MEMORY instead of MT_NON_CACHEABLE or MT_DEVICE. Apparently
> Qualcomm's normal TZ implementation maps the memory as non-cachable.
>
> Let's add the "dma-coherent" attribute to the SCM for trogdor.
>
> Adding "dma-coherent" like this fixes WiFi on sc7180-trogdor
> devices. WiFi was broken as of commit 7bd6680b47fa ("Revert "Revert
> "arm64: dma: Drop cache invalidation from
> arch_dma_prep_coherent()"""). Specifically at bootup we'd get:
>
>  qcom_scm firmware:scm: Assign memory protection call failed -22
>  qcom_rmtfs_mem 94600000.memory: assign memory failed
>  qcom_rmtfs_mem: probe of 94600000.memory failed with error -22
>
> From discussion on the mailing lists [2] and over IRC [3], it was
> determined that we should always have been tagging the SCM as
> dma-coherent on trogdor but that the old "invalidate" happened to make
> things work most of the time. Tagging it properly like this is a much
> more robust solution.
>
> [1] https://chromium.googlesource.com/chromiumos/third_party/arm-trusted-firmware/+/refs/heads/firmware-trogdor-13577.B/plat/qti/common/src/qti_syscall.c
> [2] https://lore.kernel.org/r/20230614165904.1.I279773c37e2c1ed8fbb622ca6d1397aea0023526@changeid
> [3] https://oftc.irclog.whitequark.org/linux-msm/2023-06-15
>
> Fixes: 7bd6680b47fa ("Revert "Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()""")
> Fixes: 7ec3e67307f8 ("arm64: dts: qcom: sc7180-trogdor: add initial trogdor and lazor dt")
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> ---
>
>  arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 4 ++++
>  arch/arm64/boot/dts/qcom/sc7180.dtsi         | 2 +-
>  2 files changed, 5 insertions(+), 1 deletion(-)

Shoot. I just realized I probably need a bindings update too. If this
looks good other than that, I'll post a v2 tomorrow.

-Doug