linux-kernel - Re: [PATCH v4 7/8] drm/mediatek: Add programming flow for unsupported subsys ID hardware

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Message-ID: <d1c2dfa8-c7e0-40b2-8b39-c04854e3ee24@collabora.com>
Date: Thu, 6 Mar 2025 10:47:47 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Jason-JH Lin <jason-jh.lin@...iatek.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Jassi Brar <jassisinghbrar@...il.com>,
 Chun-Kuang Hu <chunkuang.hu@...nel.org>,
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Matthias Brugger <matthias.bgg@...il.com>,
 Nancy Lin <nancy.lin@...iatek.com>, Singo Chang <singo.chang@...iatek.com>,
 Moudy Ho <moudy.ho@...iatek.com>, Xavier Chang <xavier.chang@...iatek.com>,
 Xiandong Wang <xiandong.wang@...iatek.com>,
 Sirius Wang <sirius.wang@...iatek.com>, Fei Shao <fshao@...omium.org>,
 Pin-yen Lin <treapking@...omium.org>,
 Project_Global_Chrome_Upstream_Group@...iatek.com,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
 CK Hu <ck.hu@...iatek.com>
Subject: Re: [PATCH v4 7/8] drm/mediatek: Add programming flow for unsupported
 subsys ID hardware

Il 18/02/25 06:41, Jason-JH Lin ha scritto:
> To support hardware without subsys IDs on new SoCs, add a programming
> flow that checks whether the subsys ID is valid. If the subsys ID is
> invalid, the flow will call 2 alternative CMDQ APIs:
> cmdq_pkt_assign() and cmdq_pkt_write_s_value() to achieve the same
> functionality.
> 
> Signed-off-by: Jason-JH Lin <jason-jh.lin@...iatek.com>
> Reviewed-by: CK Hu <ck.hu@...iatek.com>
> ---
>   drivers/gpu/drm/mediatek/mtk_ddp_comp.c | 33 ++++++++++++++++++++-----
>   1 file changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_ddp_comp.c b/drivers/gpu/drm/mediatek/mtk_ddp_comp.c
> index edc6417639e6..219d67735a54 100644
> --- a/drivers/gpu/drm/mediatek/mtk_ddp_comp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_ddp_comp.c
> @@ -66,14 +66,37 @@ struct mtk_ddp_comp_dev {
>   	struct cmdq_client_reg cmdq_reg;
>   };
>   
> +#if IS_REACHABLE(CONFIG_MTK_CMDQ)
> +static void mtk_ddp_write_cmdq_pkt(struct cmdq_pkt *cmdq_pkt, struct cmdq_client_reg *cmdq_reg,
> +				   unsigned int offset, unsigned int value, unsigned int mask)
> +{
> +	offset += cmdq_reg->offset;
> +
> +	if (cmdq_reg->subsys != CMDQ_SUBSYS_INVALID) {
> +		if (mask == GENMASK(31, 0))
> +			cmdq_pkt_write(cmdq_pkt, cmdq_reg->subsys, offset, value);
> +		else
> +			cmdq_pkt_write_mask(cmdq_pkt, cmdq_reg->subsys, offset, value, mask);

Sorry but this is pointless, really...

Function cmdq_pkt_write_mask() in mtk-cmdq-helper is doing:

	if (mask != GENMASK(31, 0)) {
		err = cmdq_pkt_mask(pkt, mask);
		if (err < 0)
			return err;

		offset_mask |= CMDQ_WRITE_ENABLE_MASK;
	}
	return cmdq_pkt_write(pkt, subsys, offset_mask, value);

here you're doing the exact inverse check.

At this point you can just do:

static int mtk_ddp_write_cmdq_pkt(struct cmdq_pkt *cmdq_pkt, struct cmdq_client_reg 
*cmdq_reg,
				  u16 offset, u32 value, u32 mask)
{
	u16 gce_offset = cmdq_reg->offset + offset;

	if (cmdq_reg->subsys != CMDQ_SUBSYS_INVALID)
		return cmdq_pkt_write_mask(pkt, cmdq_reg->subsys, gce_offset, value, mask);

	return cmdq_pkt_write_mask_pa(cmdq_pkt, cmdq_reg->pa_base, gce_offset, value, mask);
}

Cheers,
Angelo

> +	} else {
> +		/* only MMIO access, no need to check mminfro_offset */
> +		cmdq_pkt_assign(cmdq_pkt, 0, CMDQ_ADDR_HIGH(cmdq_reg->pa_base));
> +		if (mask == GENMASK(31, 0))
> +			cmdq_pkt_write_s_value(cmdq_pkt, CMDQ_THR_SPR_IDX0,
> +					       CMDQ_ADDR_LOW(offset), value);
> +		else
> +			cmdq_pkt_write_s_mask_value(cmdq_pkt, CMDQ_THR_SPR_IDX0,
> +						    CMDQ_ADDR_LOW(offset), value, mask);
> +	}
> +}
> +#endif
> +
>   void mtk_ddp_write(struct cmdq_pkt *cmdq_pkt, unsigned int value,
>   		   struct cmdq_client_reg *cmdq_reg, void __iomem *regs,
>   		   unsigned int offset)
>   {
>   #if IS_REACHABLE(CONFIG_MTK_CMDQ)
>   	if (cmdq_pkt)
> -		cmdq_pkt_write(cmdq_pkt, cmdq_reg->subsys,
> -			       cmdq_reg->offset + offset, value);
> +		mtk_ddp_write_cmdq_pkt(cmdq_pkt, cmdq_reg, offset, value, GENMASK(31, 0));
>   	else
>   #endif
>   		writel(value, regs + offset);
> @@ -85,8 +108,7 @@ void mtk_ddp_write_relaxed(struct cmdq_pkt *cmdq_pkt, unsigned int value,
>   {
>   #if IS_REACHABLE(CONFIG_MTK_CMDQ)
>   	if (cmdq_pkt)
> -		cmdq_pkt_write(cmdq_pkt, cmdq_reg->subsys,
> -			       cmdq_reg->offset + offset, value);
> +		mtk_ddp_write_cmdq_pkt(cmdq_pkt, cmdq_reg, offset, value, GENMASK(31, 0));
>   	else
>   #endif
>   		writel_relaxed(value, regs + offset);
> @@ -98,8 +120,7 @@ void mtk_ddp_write_mask(struct cmdq_pkt *cmdq_pkt, unsigned int value,
>   {
>   #if IS_REACHABLE(CONFIG_MTK_CMDQ)
>   	if (cmdq_pkt) {
> -		cmdq_pkt_write_mask(cmdq_pkt, cmdq_reg->subsys,
> -				    cmdq_reg->offset + offset, value, mask);
> +		mtk_ddp_write_cmdq_pkt(cmdq_pkt, cmdq_reg, offset, value, mask);
>   	} else {
>   #endif
>   		u32 tmp = readl(regs + offset);