Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) client-ip=2620:137:e000::3:5;
MIME-Version: 1.0
References: <20231114150130.497915-1-sui.jingfeng@linux.dev>
 <20231114150130.497915-6-sui.jingfeng@linux.dev> <CAA8EJprkDpjuHEi5R01p4XNvFBr94BvXhr7AZCLr6dC8Mk=yPw@mail.gmail.com>
 <7602cd83-0e05-4e11-9bd1-10eb1d48a507@linux.dev> <CAA8EJprFjdrQtegJd5HyzGYQaMawwQOhvkE=SNqsdsBCrtfDTA@mail.gmail.com>
 <14f859f2-6661-4955-932b-1ae22ae134fe@linux.dev>
In-Reply-To: <14f859f2-6661-4955-932b-1ae22ae134fe@linux.dev>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Thu, 23 Nov 2023 09:48:43 +0200
Message-ID: <CAA8EJppnB-FbnS20eJg1jwKP7pQwV_etYkQg2YW75SEO8kF9MA@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, 23 Nov 2023 at 07:37, Sui Jingfeng <sui.jingfeng@linux.dev> wrote:
>
> Hi,
>
>
> On 2023/11/16 21:00, Dmitry Baryshkov wrote:
> > 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.
>
> Sinceit6610 was introduced, how do you know what the device it66121 driver is
> binding? Printing model specific information is common practice for a
> large driver. Especially if you can only able to debug remotely where
> only a SSH is given.

cat /sys/bus/i2c/devices/.../name

> You could see debugfs of drm/etnaviv for a
> reference. It is common to testing a large driver running on 20+
> machines with various hardware model.
>
>
> >>
> >>>>                   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