| Message ID | 20220307155653.460910-1-angelogioacchino.delregno@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | media: platform: mtk-mdp: Fix mdp_ipi_comm structure alignment | expand |
Il 07/03/22 16:56, AngeloGioacchino Del Regno ha scritto: > 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> Hello, is there any issue with this patch? Regards, Angelo > --- > > This patch has been tested on Acer Chromebook R 13 (MT8173 Elm) on Debian Sid. > > This is an alternative solution to the mtk-vpu approach, found here: > https://lore.kernel.org/all/20210920170408.1561-1-dafna.hirschfeld@collabora.com > > 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; > }; > > /**
Dear Angelo, On Thu, 2022-04-21 at 13:03 +0200, AngeloGioacchino Del Regno wrote: > Il 07/03/22 16:56, AngeloGioacchino Del Regno ha scritto: > > 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> > > Hello, > is there any issue with this patch? > > Regards, > Angelo > > > --- > > > > This patch has been tested on Acer Chromebook R 13 (MT8173 Elm) on > > Debian Sid. > > > > This is an alternative solution to the mtk-vpu approach, found > > here: > > https://lore.kernel.org/all/20210920170408.1561-1-dafna.hirschfeld@collabora.com > > > > 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; > > }; > > > > /** The struct definition should be keep align between Kernel and User(sizeof(kernel) == sizeof(md32)), for backward compatible, the new "padding" variable can't be accessed by Kernel and md32, just for alignment padding in kernel side. Reviewed-by: Irui Wang <irui.wang@mediatek.com> >
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; }; /**
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> --- This patch has been tested on Acer Chromebook R 13 (MT8173 Elm) on Debian Sid. This is an alternative solution to the mtk-vpu approach, found here: https://lore.kernel.org/all/20210920170408.1561-1-dafna.hirschfeld@collabora.com drivers/media/platform/mtk-mdp/mtk_mdp_ipi.h | 2 ++ 1 file changed, 2 insertions(+)