On Sun, Oct 27, 2024 at 11:35:47PM +0530, Akhil P Oommen wrote:
> Clang-19 and above sometimes end up with multiple copies of the large
> a6xx_hfi_msg_bw_table structure on the stack. The problem is that
> a6xx_hfi_send_bw_table() calls a number of device specific functions to
> fill the structure, but these create another copy of the structure on
> the stack which gets copied to the first.
>
> If the functions get inlined, that busts the warning limit:
>
> drivers/gpu/drm/msm/adreno/a6xx_hfi.c:631:12: error: stack frame size (1032) exceeds limit (1024) in 'a6xx_hfi_send_bw_table' [-Werror,-Wframe-larger-than]
>
> Fix this by kmalloc-ating struct a6xx_hfi_msg_bw_table instead of using
> the stack. Also, use this opportunity to skip re-initializing this table
> to optimize gpu wake up latency.
>
> Cc: Arnd Bergmann <arnd@xxxxxxxxxx>
>
> Signed-off-by: Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/msm/adreno/a6xx_gmu.h | 1 +
> drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 34 ++++++++++++++++++++++------------
> 2 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> index 94b6c5cab6f4..b4a79f88ccf4 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> @@ -99,6 +99,7 @@ struct a6xx_gmu {
> struct completion pd_gate;
>
> struct qmp *qmp;
> + struct a6xx_hfi_msg_bw_table *bw_table;
> };
>
> static inline u32 gmu_read(struct a6xx_gmu *gmu, u32 offset)
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> index cdb3f6e74d3e..55e51c81be1f 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> @@ -630,32 +630,42 @@ static void a6xx_build_bw_table(struct a6xx_hfi_msg_bw_table *msg)
>
> static int a6xx_hfi_send_bw_table(struct a6xx_gmu *gmu)
> {
> - struct a6xx_hfi_msg_bw_table msg = { 0 };
> + struct a6xx_hfi_msg_bw_table *msg;
> struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu, gmu);
> struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
>
> + if (gmu->bw_table)
> + goto send;
> +
> + msg = devm_kzalloc(gmu->dev, sizeof(*msg), GFP_KERNEL);
Is it necessary after being sent? Isn't it better to just kzalloc() it
and then kfree() it at the end of the function?
> + if (!msg)
> + return -ENOMEM;
> +
> if (adreno_is_a618(adreno_gpu))
> - a618_build_bw_table(&msg);
> + a618_build_bw_table(msg);
> else if (adreno_is_a619(adreno_gpu))
> - a619_build_bw_table(&msg);
> + a619_build_bw_table(msg);
> else if (adreno_is_a640_family(adreno_gpu))
> - a640_build_bw_table(&msg);
> + a640_build_bw_table(msg);
> else if (adreno_is_a650(adreno_gpu))
> - a650_build_bw_table(&msg);
> + a650_build_bw_table(msg);
> else if (adreno_is_7c3(adreno_gpu))
> - adreno_7c3_build_bw_table(&msg);
> + adreno_7c3_build_bw_table(msg);
> else if (adreno_is_a660(adreno_gpu))
> - a660_build_bw_table(&msg);
> + a660_build_bw_table(msg);
> else if (adreno_is_a690(adreno_gpu))
> - a690_build_bw_table(&msg);
> + a690_build_bw_table(msg);
> else if (adreno_is_a730(adreno_gpu))
> - a730_build_bw_table(&msg);
> + a730_build_bw_table(msg);
> else if (adreno_is_a740_family(adreno_gpu))
> - a740_build_bw_table(&msg);
> + a740_build_bw_table(msg);
> else
> - a6xx_build_bw_table(&msg);
> + a6xx_build_bw_table(msg);
> +
> + gmu->bw_table = msg;
>
> - return a6xx_hfi_send_msg(gmu, HFI_H2F_MSG_BW_TABLE, &msg, sizeof(msg),
> +send:
> + return a6xx_hfi_send_msg(gmu, HFI_H2F_MSG_BW_TABLE, gmu->bw_table, sizeof(*(gmu->bw_table)),
> NULL, 0);
> }
>
>
> ---
> base-commit: 74c374648ed08efb2ef339656f2764c28c046956
> change-id: 20241024-stack-size-fix-28af7abd3fab
>
> Best regards,
> --
> Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx>
>
--
With best wishes
Dmitry
