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

[Sui Jingfeng]

Hi,


On 2023/11/16 21:00, Dmitry Baryshkov wrote:
> On Thu, 16 Nov 2023 at 14:18, Sui Jingfeng <sui.jingfeng@xxxxxxxxx> wrote:
> > Hi,
> >
> >
> > On 2023/11/15 00:06, Dmitry Baryshkov wrote:
> > > On Tue, 14 Nov 2023 at 17:09, Sui Jingfeng <sui.jingfeng@xxxxxxxxx> wrote:
> > > > From: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
> > > >
> > > > 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@xxxxxxxxxxx>
> > > > ---
> > > >    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. 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