linux-kernel - Re: [PATCH 4/8] soc: mediatek: mtk-cmdq: Add unsupported subsys ID programing flow

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Message-ID: <f637f72960e84efb88dc6ed8482ea7a0d6bfcd25.camel@mediatek.com>
Date: Thu, 21 Nov 2024 06:38:07 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>, "mchehab@...nel.org"
	<mchehab@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
	"robh@...nel.org" <robh@...nel.org>, "matthias.bgg@...il.com"
	<matthias.bgg@...il.com>, "jassisinghbrar@...il.com"
	<jassisinghbrar@...il.com>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	Singo Chang (張興國) <Singo.Chang@...iatek.com>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, "simona@...ll.ch"
	<simona@...ll.ch>, Moudy Ho (何宗原)
	<Moudy.Ho@...iatek.com>, Nancy Lin (林欣螢)
	<Nancy.Lin@...iatek.com>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>, "airlied@...il.com"
	<airlied@...il.com>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 4/8] soc: mediatek: mtk-cmdq: Add unsupported subsys ID
 programing flow

Hi, Jason:

On Thu, 2024-11-21 at 12:25 +0800, Jason-JH.Lin wrote:
> When GCE executes instructions, the corresponding hardware register
> can be found through the subsys ID.
> For unsupported subsys ID hardware, the physical address need to be used
> to generate GCE instructions.
> 
> Add the pa_base interface to the instruction programming flow for these
> unsupported subsys ID hardware.
> 
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> ---

[snip]

> -int cmdq_pkt_write(struct cmdq_pkt *pkt, u8 subsys, u16 offset, u32 value)
> +int cmdq_pkt_write(struct cmdq_pkt *pkt, u8 subsys, u32 pa_base, u16 offset, u32 value)
>  {
> +	struct cmdq_client *cl = (struct cmdq_client *)pkt->cl;
>  	struct cmdq_instruction inst = {
>  		.op = CMDQ_CODE_WRITE,
>  		.value = value,
>  		.offset = offset,
>  		.subsys = subsys
>  	};
> -	return cmdq_pkt_append_command(pkt, inst);
> +	int err;
> +
> +	if (!cl) {
> +		pr_err("%s %d: pkt->cl is NULL!\n", __func__, __LINE__);
> +		return -EINVAL;
> +	}
> +
> +	if (cmdq_subsys_is_valid(cl->chan, subsys)) {

I would like to have a new API for no subsys. Maybe cmdq_pkt_write_pa().
If some client driver always have subsys, it could use cmdq_pkt_write().
If some client driver have no subsys, it could use cmdq_pkt_write_pa().
This would prevent frequently conditional jump in this function.
If some client driver have subsys in some SoC and have no subsys in other SoC,
let the conditional jump happen in that client driver.
(The client driver could use 'likely' or 'unlikely' to uptimize)
In the view point to let client driver have fine-grained control,
maybe client could use cmdq_pkt_assign() and cmdq_pkt_write_s_value() to achieve this so it's not necessary to invent new API.

Regards,
CK

> +		err = cmdq_pkt_append_command(pkt, inst);
> +	} else {
> +		err = cmdq_pkt_assign(pkt, 0, CMDQ_ADDR_HIGH(pa_base));
> +		if (err < 0)
> +			return err;
> +
> +		err = cmdq_pkt_write_s_value(pkt, 0, CMDQ_ADDR_LOW(offset), value);
> +	}
> +
> +	return err;
>  }
>  EXPORT_SYMBOL(cmdq_pkt_write);
>