Re: [PATCH 1/3] memory: tegra186-emc: stop borrowing MC aggregate hook for EMC

[Krzysztof Kozlowski <krzk@kernel.org>]

On 27/05/2026 16:01, Sumit Gupta wrote:
> tegra186_emc_interconnect_init() copies the MC's ICC aggregate hook
> into the EMC provider.  That hook (tegra234_mc_icc_aggregate /
> tegra264_mc_icc_aggregate) uses container_of() to recover 'mc',
> which is only valid when the icc_provider is embedded in struct
> tegra_mc.  For an EMC node the provider is embedded in struct
> tegra186_emc, so 'mc' points into unrelated memory.
> 
> This stayed harmless until commit faafd6ca7e6e ("memory: tegra:
> make icc_set_bw return zero if BWMGR not supported") added an
> unconditional read of mc->bwmgr_mrq_supported at the top of the
> hook.  UBSAN catches the stray load on every EMC aggregation:
> 
>   UBSAN: invalid-load in drivers/memory/tegra/tegra234.c:1104:9
>   load of value 112 is not a valid value for type '_Bool'
> 
> No functional impact in practice, since the hook's only other mc
> dereference (mc->num_channels) sits inside a
> TEGRA_ICC_MC_CPU_CLUSTER* branch that EMC nodes never enter.
> 
> Fix this by setting the EMC provider's aggregate hook to
> icc_std_aggregate, instead of borrowing the MC's hook.  The MC
> providers continue using their own aggregate hooks, where
> container_of() correctly resolves to struct tegra_mc.
> 
> Reported-by: Jon Hunter <jonathanh@nvidia.com>

I assume these reports were offlist. Otherwise this has a valid
checkpatch warning.

Best regards,
Krzysztof