linux-kernel - Re: [PATCH v2 10/11] drm/mediatek: Add cmdq_insert_backup

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Date:   Thu, 26 Oct 2023 02:26:54 +0000
From:   CK Hu (胡俊光) <ck.hu@...iatek.com>
To:     "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        Jason-JH Lin (林睿祥) 
        <Jason-JH.Lin@...iatek.com>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Jason-ch Chen (陳建豪) 
        <Jason-ch.Chen@...iatek.com>,
        Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
        Johnson Wang (王聖鑫) 
        <Johnson.Wang@...iatek.com>,
        "jkardatzke@...gle.com" <jkardatzke@...gle.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 10/11] drm/mediatek: Add cmdq_insert_backup_cookie
 before secure pkt finalize

Hi, Jason:

On Mon, 2023-10-23 at 12:45 +0800, Jason-JH.Lin wrote:
> Add cmdq_insert_backup_cookie to append some commands before EOC:
> 1. Get GCE HW thread execute count from the GCE HW register.
> 2. Add 1 to the execute count and then store into a shared memory.

I think when cmdq driver handler interrupt, it could simply call into
TEE with an API to query status. The status not only the execute count,
but also other message including error information. So it's not
necessary to use such non-tricky way to get execute count.

One more question. The command buffer is not secure. Does the GCE
hardware execute this non-secure command buffer?

Regards,
CK

> 3. Set a software event siganl as secure irq to GCE HW.
> 
> Since the value of execute count + 1 is stored in a shared memory,
> CMDQ driver in the normal world can use it to handle task done in irq
> handler and CMDQ driver in the secure world will use it to schedule
> the task slot for each secure thread.
> 
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index 6c2cf339b923..399aa6bb2f8d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -177,7 +177,7 @@ void mtk_crtc_disable_secure_state(struct
> drm_crtc *crtc)
>  		sec_scn = CMDQ_SEC_SUB_DISP_DISABLE;
>  
>  	cmdq_sec_pkt_set_data(&mtk_crtc->sec_cmdq_handle, sec_engine,
> sec_engine, sec_scn);
> -
> +	cmdq_sec_insert_backup_cookie(&mtk_crtc->sec_cmdq_handle);
>  	cmdq_pkt_finalize(&mtk_crtc->sec_cmdq_handle);
>  	dma_sync_single_for_device(mtk_crtc->sec_cmdq_client.chan-
> >mbox->dev,
>  				   mtk_crtc->sec_cmdq_handle.pa_base,
> @@ -786,6 +786,8 @@ static void mtk_drm_crtc_update_config(struct
> mtk_drm_crtc *mtk_crtc,
>  		cmdq_pkt_clear_event(cmdq_handle, mtk_crtc-
> >cmdq_event);
>  		cmdq_pkt_wfe(cmdq_handle, mtk_crtc->cmdq_event, false);
>  		mtk_crtc_ddp_config(crtc, cmdq_handle);
> +		if (cmdq_handle->sec_data)
> +			cmdq_sec_insert_backup_cookie(cmdq_handle);
>  		cmdq_pkt_finalize(cmdq_handle);
>  		dma_sync_single_for_device(cmdq_client.chan->mbox->dev,
>  					   cmdq_handle->pa_base,