linux-kernel - Re: [PATCH v25 2/2] soc: mediatek: Add Mediatek CMDQ helper

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Message-ID: <7040427b-f580-ec33-8afa-35dcf5735abb@gmail.com>
Date:   Sat, 29 Sep 2018 14:50:35 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Houlong Wei <houlong.wei@...iatek.com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Daniel Kurtz <djkurtz@...omium.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        Sascha Hauer <kernel@...gutronix.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Nicolas Boichat <drinkcat@...omium.org>,
        CK HU <ck.hu@...iatek.com>,
        Bibby Hsieh <bibby.hsieh@...iatek.com>,
        YT Shen <yt.shen@...iatek.com>,
        Daoyuan Huang <daoyuan.huang@...iatek.com>,
        Jiaguang Zhang <jiaguang.zhang@...iatek.com>,
        Dennis-YC Hsieh <dennis-yc.hsieh@...iatek.com>,
        Monica Wang <monica.wang@...iatek.com>,
        HS Liao <hs.liao@...iatek.com>, ginny.chen@...iatek.com,
        enzhu.wang@...iatek.com
Subject: Re: [PATCH v25 2/2] soc: mediatek: Add Mediatek CMDQ helper



On 29/09/2018 11:21, Houlong Wei wrote:
[...]

> +static int cmdq_pkt_append_command(struct cmdq_pkt *pkt, enum cmdq_code code,
> +				   u32 arg_a, u32 arg_b)
> +{
> +	u64 *cmd_ptr;
> +
> +	if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE > pkt->buf_size)) {
> +		pkt->cmd_buf_size += CMDQ_INST_SIZE;

Can you plesae provide some example code of a driver that will use this API, I
still don't understand why you need to update the cmd_buf_size here.

> +		WARN_ON(1);

can we add some debug information:
WARN_ON(1, "%s: buffer size too small for the amount of commands", __func__);

Would it make sense to use WARN_ONCE()?

> +		return -ENOMEM;
> +	}
> +	cmd_ptr = pkt->va_base + pkt->cmd_buf_size;
> +	(*cmd_ptr) = (u64)((code << CMDQ_OP_CODE_SHIFT) | arg_a) << 32 | arg_b;
> +	pkt->cmd_buf_size += CMDQ_INST_SIZE;
> +
> +	return 0;
> +}

Thanks,
Matthias