linux-kernel - Re: [PATCH v4 5/8] drm/mediatek: hdmi: add v2 support

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Message-ID: <72a13a42260d39c2495c59241d661f3a7a18c492.camel@mediatek.com>
Date:   Tue, 13 Jun 2023 02:19:10 +0000
From:   CK Hu (胡俊光) <ck.hu@...iatek.com>
To:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "kishon@...com" <kishon@...com>,
        Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        Jitao Shi (石记涛) <jitao.shi@...iatek.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "granquet@...libre.com" <granquet@...libre.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "airlied@...il.com" <airlied@...il.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Mac Shen (沈俊) <Mac.Shen@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        Stuart Lee (李翰) <Stuart.Lee@...iatek.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v4 5/8] drm/mediatek: hdmi: add v2 support

Hi, Guillaume:

On Mon, 2023-05-29 at 16:31 +0200, Guillaume Ranquet wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  Adds hdmi and hdmi-ddc support for v2 IP.
> 
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> ---

[snip]

> +
> +static bool fg_ddc_data_read(struct mtk_hdmi_ddc *ddc,
> +      unsigned char b_dev,
> +      unsigned char b_data_addr,
> +      unsigned char b_data_count,
> +      unsigned char *pr_data)
> +{
> +int ret;
> +
> +mutex_lock(&ddc->mtx);

Why do you need this mutex? fg_ddc_data_read() and fg_ddc_data_write()
are called by mtk_hdmi_ddc_xfer() which is the callback function of
master_xfer. In original hdmi driver, it's not necessary to use a mutex
to protect master_xfer, so I think this is not necessary.

Regards,
CK

> +
> +hdmi_ddc_request(ddc);
> +ret = vddc_read(ddc, DDC2_CLOK, b_dev, b_data_addr, SIF_8_BIT_HDMI,
> +      pr_data, b_data_count);
> +mutex_unlock(&ddc->mtx);
> +
> +return ret == b_data_count;
> +}
> +
> +static void fg_ddc_data_write(struct mtk_hdmi_ddc *ddc,
> +       unsigned char b_dev,
> +       unsigned char b_data_addr,
> +       unsigned char b_data_count,
> +       unsigned char *pr_data)
> +{
> +unsigned int i;
> +
> +mutex_lock(&ddc->mtx);
> +
> +hdmi_ddc_request(ddc);
> +for (i = 0; i < b_data_count; i++)
> +mtk_ddc_wr_one(ddc, b_dev, b_data_addr + i, *(pr_data + i));
> +
> +mutex_unlock(&ddc->mtx);
> +}
> +
> +static int mtk_hdmi_ddc_xfer(struct i2c_adapter *adapter, struct
> i2c_msg *msgs,
> +     int num)
> +{
> +struct mtk_hdmi_ddc *ddc = adapter->algo_data;
> +struct device *dev = adapter->dev.parent;
> +bool ret;
> +int i;
> +unsigned char offset;
> +
> +if (!ddc)
> +return -EINVAL;
> +
> +for (i = 0; i < num; i++) {
> +struct i2c_msg *msg = &msgs[i];
> +
> +if (msg->flags & I2C_M_RD) {
> +/* The underlying DDC hardware always issue a write request
> + * that assigns the read offset as part of the read operation.
> + * Therefore we need to use the offset value assigned
> + * in the previous write request from the drm_edid.c
> + */
> +ret = fg_ddc_data_read(ddc, msg->addr,
> +       offset, /* determined by previous write requests */
> +       (msg->len), &msg->buf[0]);
> +if (!ret) {
> +dev_err(dev, "ddc read failed : %d\n", ret);
> +return ret;
> +}
> +} else {
> +fg_ddc_data_write(ddc, msg->addr, msg->buf[0],
> +(msg->len - 1), &msg->buf[1]);
> +
> +/* we store the offset value requested by drm_edid framework
> + * to use in subsequent read requests.
> + */
> +if (DDC_ADDR == msg->addr && 1 == msg->len)
> +offset = msg->buf[0];
> +}
> +}
> +
> +return i;
> +}
> +