linux-kernel - Re: [PATCH 5/8] drm/bridge: it66121: Add a helper function to read chip id

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Message-ID: <CAA8EJprkDpjuHEi5R01p4XNvFBr94BvXhr7AZCLr6dC8Mk=yPw@mail.gmail.com>
Date:   Tue, 14 Nov 2023 18:06:37 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Sui Jingfeng <sui.jingfeng@...ux.dev>
Cc:     Phong LE <ple@...libre.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Maxime Ripard <mripard@...nel.org>,
        Sui Jingfeng <suijingfeng@...ngson.cn>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH 5/8] drm/bridge: it66121: Add a helper function to read
 chip id

On Tue, 14 Nov 2023 at 17:09, Sui Jingfeng <sui.jingfeng@...ux.dev> wrote:
>
> From: Sui Jingfeng <suijingfeng@...ngson.cn>
>
> Read the required chip id data back by calling regmap_bulk_read() once,
> reduce the number of local variables needed in it66121_probe() function.
> And store its values into struct it66121_ctx, as it will be used latter.
>
> Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
> ---
>  drivers/gpu/drm/bridge/ite-it66121.c | 47 ++++++++++++++++++++--------
>  1 file changed, 34 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/ite-it66121.c b/drivers/gpu/drm/bridge/ite-it66121.c
> index 7e473beefc79..f36d05331f25 100644
> --- a/drivers/gpu/drm/bridge/ite-it66121.c
> +++ b/drivers/gpu/drm/bridge/ite-it66121.c
> @@ -313,6 +313,9 @@ struct it66121_ctx {
>                 bool auto_cts;
>         } audio;
>         const struct it66121_chip_info *info;
> +       u16 vender_id;
> +       u16 device_id;
> +       u8 revision;

There is no need to store them, they are not used by the driver anywhere.

>  };
>
>  static inline struct it66121_ctx *bridge_to_it66121(struct drm_bridge *bridge)
> @@ -399,6 +402,30 @@ static void it66121_hw_reset(struct it66121_ctx *ctx)
>         gpiod_set_value(ctx->gpio_reset, 0);
>  }
>
> +static int it66121_read_chip_id(struct it66121_ctx *ctx, bool verbose)
> +{
> +       u8 id[4];
> +       int ret;
> +
> +       ret = regmap_bulk_read(ctx->regmap, IT66121_VENDOR_ID0_REG, id, 4);
> +       if (ret < 0) {
> +               dev_err(ctx->dev, "Failed to read chip ID: %d\n", ret);
> +               return ret;
> +       }
> +
> +       ctx->vender_id = (u16)id[1] << 8 | id[0];
> +       ctx->device_id = ((u16)(id[3] & IT66121_DEVICE_ID1_MASK) << 8 | id[2]);
> +       /* Revision is shared with DEVICE_ID1 */
> +       ctx->revision = FIELD_GET(IT66121_REVISION_MASK, id[3]);
> +
> +       if (verbose) {
> +               dev_info(ctx->dev, "Found ITE66121: 0x%x%x, revision: %u\n",
> +                        ctx->vender_id, ctx->device_id, ctx->revision);
> +       }
> +
> +       return 0;
> +}
> +
>  static inline int it66121_preamble_ddc(struct it66121_ctx *ctx)
>  {
>         return regmap_write(ctx->regmap, IT66121_MASTER_SEL_REG, IT66121_MASTER_SEL_HOST);
> @@ -1561,7 +1588,6 @@ static const char * const it66121_supplies[] = {
>
>  static int it66121_probe(struct i2c_client *client)
>  {
> -       u32 revision_id, vendor_ids[2] = { 0 }, device_ids[2] = { 0 };
>         int ret;
>         struct it66121_ctx *ctx;
>         struct device *dev = &client->dev;
> @@ -1603,19 +1629,13 @@ static int it66121_probe(struct i2c_client *client)
>         if (IS_ERR(ctx->regmap))
>                 return PTR_ERR(ctx->regmap);
>
> -       regmap_read(ctx->regmap, IT66121_VENDOR_ID0_REG, &vendor_ids[0]);
> -       regmap_read(ctx->regmap, IT66121_VENDOR_ID1_REG, &vendor_ids[1]);
> -       regmap_read(ctx->regmap, IT66121_DEVICE_ID0_REG, &device_ids[0]);
> -       regmap_read(ctx->regmap, IT66121_DEVICE_ID1_REG, &device_ids[1]);
> -
> -       /* Revision is shared with DEVICE_ID1 */
> -       revision_id = FIELD_GET(IT66121_REVISION_MASK, device_ids[1]);
> -       device_ids[1] &= IT66121_DEVICE_ID1_MASK;
> +       ret = it66121_read_chip_id(ctx, false);
> +       if (ret)
> +               return ret;
>
> -       if ((vendor_ids[1] << 8 | vendor_ids[0]) != ctx->info->vid ||
> -           (device_ids[1] << 8 | device_ids[0]) != ctx->info->pid) {
> +       if (ctx->vender_id != ctx->info->vid ||
> +           ctx->device_id != ctx->info->pid)
>                 return -ENODEV;
> -       }
>
>         ctx->bridge.funcs = &it66121_bridge_funcs;
>         ctx->bridge.of_node = dev->of_node;
> @@ -1633,7 +1653,8 @@ static int it66121_probe(struct i2c_client *client)
>
>         drm_bridge_add(&ctx->bridge);
>
> -       dev_info(dev, "IT66121 revision %d probed\n", revision_id);
> +       dev_info(dev, "IT66121 probed, chip id: 0x%x:0x%x, revision: %u\n",
> +                ctx->vender_id, ctx->device_id, ctx->revision);
>
>         return 0;
>  }
> --
> 2.34.1
>


-- 
With best wishes
Dmitry