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    Subject[PATCH 5.10 221/545] media: platform: mtk-mdp: Fix mdp_ipi_comm structure alignment
    Date
    From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

    [ Upstream commit ab14c99c035da7156a3b66fa171171295bc4b89a ]

    The mdp_ipi_comm structure defines a command that is either
    PROCESS (start processing) or DEINIT (destroy instance); we
    are using this one to send PROCESS or DEINIT commands from Linux
    to an MDP instance through a VPU write but, while the first wants
    us to stay 4-bytes aligned, the VPU instead requires an 8-bytes
    data alignment.

    Keeping in mind that these commands are executed immediately
    after sending them (hence not chained with others before the
    VPU/MDP "actually" start executing), it is fine to simply add
    a padding of 4 bytes to this structure: this keeps the same
    performance as before, as we're still stack-allocating it,
    while avoiding hackery inside of mtk-vpu to ensure alignment
    bringing a definitely bigger performance impact.

    Fixes: c8eb2d7e8202 ("[media] media: Add Mediatek MDP Driver")
    Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
    Reviewed-by: Houlong Wei <houlong.wei@mediatek.com>
    Reviewed-by: Irui Wang <irui.wang@mediatek.com>
    Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
    Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/media/platform/mtk-mdp/mtk_mdp_ipi.h | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_ipi.h b/drivers/media/platform/mtk-mdp/mtk_mdp_ipi.h
    index 2cb8cecb3077..b810c96695c8 100644
    --- a/drivers/media/platform/mtk-mdp/mtk_mdp_ipi.h
    +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_ipi.h
    @@ -40,12 +40,14 @@ struct mdp_ipi_init {
    * @ipi_id : IPI_MDP
    * @ap_inst : AP mtk_mdp_vpu address
    * @vpu_inst_addr : VPU MDP instance address
    + * @padding : Alignment padding
    */
    struct mdp_ipi_comm {
    uint32_t msg_id;
    uint32_t ipi_id;
    uint64_t ap_inst;
    uint32_t vpu_inst_addr;
    + uint32_t padding;
    };

    /**
    --
    2.35.1


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