Re: [PATCH] Revert "firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module"

[Will Deacon <will@xxxxxxxxxx>]

On Thu, Nov 19, 2020 at 06:41:49PM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding@xxxxxxxxxx>
> 
> Commit d0511b5496c0 ("firmware: QCOM_SCM: Allow qcom_scm driver to be
> loadable as a permenent module") causes the ARM SMMU driver to be built
> as a loadable module when using the Aarch64 default configuration. This
> in turn causes problems because if the loadable module is not shipped
> in an initial ramdisk, then the deferred probe timeout mechanism will
> cause all SMMU masters to probe without SMMU support and fall back to
> just plain DMA ops (not IOMMU-backed).
> 
> Once the system has mounted the rootfs, the ARM SMMU driver will then
> be loaded, but since the ARM SMMU driver faults by default, this causes
> a slew of SMMU faults for the SMMU masters that have already been set
> up with plain DMA ops and cause these devices to malfunction.
> 
> Revert that commit to unbreak things while we look for an alternative
> solution.
> 
> Reported-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
> ---
>  drivers/firmware/Kconfig                | 4 ++--
>  drivers/firmware/Makefile               | 3 +--
>  drivers/firmware/qcom_scm.c             | 4 ----
>  drivers/iommu/Kconfig                   | 2 --
>  drivers/net/wireless/ath/ath10k/Kconfig | 1 -
>  5 files changed, 3 insertions(+), 11 deletions(-)

Acked-by: Will Deacon <will@xxxxxxxxxx>

John previously agreed to this here:

https://lore.kernel.org/r/CALAqxLVDm923WRSB+DVxFacmEtmEPS7Qeq+rW_jbCDMNMWw9PQ@xxxxxxxxxxxxxx

so might be worth putting in a Link: tag when it gets applied.

Will