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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Thu, 16 Nov 2023 15:00:55 +0200
Message-ID: <CAA8EJprFjdrQtegJd5HyzGYQaMawwQOhvkE=SNqsdsBCrtfDTA@mail.gmail.com>
Subject: Re: [PATCH 5/8] drm/bridge: it66121: Add a helper function to read
 chip id
To:     Sui Jingfeng <sui.jingfeng@linux.dev>
Cc:     Phong LE <ple@baylibre.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Maxime Ripard <mripard@kernel.org>,
        Sui Jingfeng <suijingfeng@loongson.cn>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Thomas Zimmermann <tzimmermann@suse.de>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, 16 Nov 2023 at 14:18, Sui Jingfeng <sui.jingfeng@linux.dev> wrote:
>
> Hi,
>
>
> On 2023/11/15 00:06, Dmitry Baryshkov wrote:
> > On Tue, 14 Nov 2023 at 17:09, Sui Jingfeng <sui.jingfeng@linux.dev> wrote:
> >> From: Sui Jingfeng <suijingfeng@loongson.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@loongson.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)
>
> Q: There is no need to store them, they are not used by the driver anywhere.
>
> A: Here it is used, it is also used by the 0007-patch to get the entity(instance)-specific data.

And the patch 7 will be changed once you have proper i2c client struct
registered.

>
>
> Since it6610 was introduced, this is used for chip identifying.
> It can also be used with in debugfs context, to show who I am.

I'd say, there is little point in whoami debugfs files. Debugfs is for
the useful information.

>
>
> >>                  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