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

Dmitry Baryshkov
2023-11-16T13:01:14Z

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