Re: [PATCH V3 4/4] drm/bridge: it66121: Add minimal it66122 support

[Andrew Davis]

On 8/14/25 10:41 PM, Nishanth Menon wrote:

The IT66122 is a pin compatible replacement for the IT66122. Based on
empirical testing, the new device looks to be compatible with IT66121.
However due to a lack of public data sheet at this time beyond overall
feature list[1] (which seems to add additional features vs ITT66121),
it is hard to determine that additional register operations required
to enable additional features.

So, introduce the device as a new compatible that we will detect based
on vid/pid match, with explicit id that can be used to extend the
driver capability as information becomes available later on.

[1] https://www.ite.com.tw/en/product/cate1/IT66122

Signed-off-by: Nishanth Menon <n...@ti.com>
---
Changes in V3:
* Dropped the claim that it is 1-1 replacement of IT66121.
* Based on emperical test result[2], introduce the same configuration of
   IT66121, but provide ID as suggested by Devarsh to allow for future
   expansion of functionality.

NOTE: I did consider the possibility of converting the chip_id into a
bitfield, but decided it is over-engineering, so kept the enum.

But over-engineering is so much more fun :D

Reviewed-by: Andrew Davis <a...@ti.com>

[2] https://github.com/beagleboard/linux/commits/v6.1.83-ti-rt-r40

V2: https://lore.kernel.org/all/20250813204106.580141-4...@ti.com/

  drivers/gpu/drm/bridge/ite-it66121.c | 14 +++++++++-----
  1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it66121.c 
b/drivers/gpu/drm/bridge/ite-it66121.c
index 5ac9631bcd9a..a108d287722d 100644
--- a/drivers/gpu/drm/bridge/ite-it66121.c
+++ b/drivers/gpu/drm/bridge/ite-it66121.c
@@ -287,6 +287,7 @@
  enum chip_id {
        ID_IT6610,
        ID_IT66121,
+       ID_IT66122,
  };

struct it66121_chip_info {

@@ -402,7 +403,7 @@ static int it66121_configure_afe(struct it66121_ctx *ctx,
                if (ret)
                        return ret;

- if (ctx->id == ID_IT66121) {

+               if (ctx->id == ID_IT66121 || ctx->id == ID_IT66122) {
                        ret = regmap_write_bits(ctx->regmap, IT66121_AFE_IP_REG,
                                                IT66121_AFE_IP_EC1, 0);
                        if (ret)
@@ -428,7 +429,7 @@ static int it66121_configure_afe(struct it66121_ctx *ctx,
                if (ret)
                        return ret;

- if (ctx->id == ID_IT66121) {

+               if (ctx->id == ID_IT66121 || ctx->id == ID_IT66122) {
                        ret = regmap_write_bits(ctx->regmap, IT66121_AFE_IP_REG,
                                                IT66121_AFE_IP_EC1,
                                                IT66121_AFE_IP_EC1);
@@ -599,7 +600,7 @@ static int it66121_bridge_attach(struct drm_bridge *bridge,
        if (ret)
                return ret;

- if (ctx->id == ID_IT66121) {

+       if (ctx->id == ID_IT66121 || ctx->id == ID_IT66122) {
                ret = regmap_write_bits(ctx->regmap, IT66121_CLK_BANK_REG,
                                        IT66121_CLK_BANK_PWROFF_RCLK, 0);
                if (ret)
@@ -802,7 +803,7 @@ void it66121_bridge_mode_set(struct drm_bridge *bridge,
        if (regmap_write(ctx->regmap, IT66121_HDMI_MODE_REG, 
IT66121_HDMI_MODE_HDMI))
                goto unlock;

- if (ctx->id == ID_IT66121 &&

+       if ((ctx->id == ID_IT66121 || ctx->id == ID_IT66122) &&
            regmap_write_bits(ctx->regmap, IT66121_CLK_BANK_REG,
                              IT66121_CLK_BANK_PWROFF_TXCLK,
                              IT66121_CLK_BANK_PWROFF_TXCLK)) {
@@ -815,7 +816,7 @@ void it66121_bridge_mode_set(struct drm_bridge *bridge,
        if (it66121_configure_afe(ctx, adjusted_mode))
                goto unlock;

- if (ctx->id == ID_IT66121 &&

+       if ((ctx->id == ID_IT66121 || ctx->id == ID_IT66122) &&
            regmap_write_bits(ctx->regmap, IT66121_CLK_BANK_REG,
                              IT66121_CLK_BANK_PWROFF_TXCLK, 0)) {
                goto unlock;
@@ -1614,12 +1615,14 @@ static void it66121_remove(struct i2c_client *client)
  }

static const struct it66121_chip_info it66xx_chip_info[] = {

+       {.id = ID_IT66122, .vid = 0x4954, .pid = 0x0622 },
        {.id = ID_IT66121, .vid = 0x4954, .pid = 0x0612 },
        {.id = ID_IT6610, .vid = 0xca00, .pid = 0x0611 },
        { }
  };

static const struct of_device_id it66121_dt_match[] = {

+       { .compatible = "ite,it66122", &it66xx_chip_info },
        { .compatible = "ite,it66121", &it66xx_chip_info },
        { .compatible = "ite,it6610", &it66xx_chip_info },
        { }
@@ -1627,6 +1630,7 @@ static const struct of_device_id it66121_dt_match[] = {
  MODULE_DEVICE_TABLE(of, it66121_dt_match);

static const struct i2c_device_id it66121_id[] = {

+       { "it66122", (kernel_ulong_t)&it66xx_chip_info },
        { "it66121", (kernel_ulong_t)&it66xx_chip_info },
        { "it6610", (kernel_ulong_t)&it66xx_chip_info },
        { }