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

Sui Jingfeng
2023-11-16T18:29:41Z

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.
>
We will create a "wrong"i2c client intentionally by calling i2c_new_client_device, the "wrong"
here means that 'board_info.type' is not equal to "it66121" or "it6610".

I probably know what you means, but please note that we are not object you at here.
The reason why we prefer theit66121_get_match_data() over the i2c_get_match_data() is that our
it66121_get_match_data() works with *the least dependency*. Ourversion
don't rely on the DT to provide compatible strings. Because the it66121 itself already
provided constant hard-coded vender id and device id on-chip register. This is a bit
similar with the PCIe devices. This chip id speak everything about chip identify.
By re-arranging the variants into array, searching and matching against became
straight-forward. We can also utilize the vender id and device id information to
dynamic bind the instance specific functions *at the setup(probe) time*. Which helps
to untangle the it66121 and it6610 cases with function object. Currently they are
tangled. This is not a problem simply because the model supported is too small(less).

>>
>> 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
>>>>
>
>