On Tue, Sep 16, 2025 at 12:47:43PM +0800, Hermes Wu via B4 Relay wrote:
> From: Hermes Wu <hermes...@ite.com.tw>
>
> IT6505 supports HW link training which will write DPCD and check
> training status automatically.
>
> In the case that driver set link rate at 2.7G and HW fail to training,
> it will change link configuration and try 1.65G. And this will cause
> INT_VID_FIFO_ERROR triggered when link clock is changed.
>
> When video error occurs, video logic is reset and link training restart,
> this will cause endless auto link training.
>
> Modify link auto training with disable INT_VID_FIFO_ERROR to avoid loop
> and check INT_LINK_TRAIN_FAIL event to abort wait training done.
>
> Signed-off-by: Hermes Wu <hermes...@ite.com.tw>
> ---
> drivers/gpu/drm/bridge/ite-it6505.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c
> b/drivers/gpu/drm/bridge/ite-it6505.c
> index
> 7f6227c278a51358c70a3de93454aafeef64f2bb..f9b99c70789eea6beb3c6513155c9a4ca103d219
> 100644
> --- a/drivers/gpu/drm/bridge/ite-it6505.c
> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> @@ -1806,6 +1806,13 @@ static bool it6505_link_start_auto_train(struct it6505
> *it6505)
> struct device *dev = it6505->dev;
>
> mutex_lock(&it6505->aux_lock);
> +
> + /* Disable FIFO error interrupt trigger */
> + /* to prevent training fail loop issue */
> + it6505_set_bits(it6505, INT_MASK_03, BIT(INT_VID_FIFO_ERROR), 0);
> +
> + it6505_write(it6505, INT_STATUS_03,
> + BIT(INT_LINK_TRAIN_FAIL) | BIT(INT_VID_FIFO_ERROR));
> it6505_set_bits(it6505, REG_TRAIN_CTRL0,
> FORCE_CR_DONE | FORCE_EQ_DONE, 0x00);
> /* reset link state machine and re start training*/
> @@ -1818,8 +1825,10 @@ static bool it6505_link_start_auto_train(struct it6505
> *it6505)
> link_training_state = it6505_read(it6505, REG_LINK_TRAIN_STS);
> int03 = it6505_read(it6505, INT_STATUS_03);
> if (int03 & BIT(INT_LINK_TRAIN_FAIL)) {
> + /* Ignore INT_VID_FIFO_ERROR when auto training fail*/
> it6505_write(it6505, INT_STATUS_03,
> - BIT(INT_LINK_TRAIN_FAIL));
> + BIT(INT_LINK_TRAIN_FAIL) |
> + BIT(INT_VID_FIFO_ERROR));
I'm really unusure about this change. Judging by the description of the
problem, it's fix for the issue, but the issue gets introduced in the
previous patch.
>
> DRM_DEV_DEBUG_DRIVER(dev,
> "INT_LINK_TRAIN_FAIL(%x)!",
> @@ -1837,6 +1846,9 @@ static bool it6505_link_start_auto_train(struct it6505
> *it6505)
> timeout--;
> }
> unlock:
> + /* recover interrupt trigger*/
> + it6505_set_bits(it6505, INT_MASK_03,
> + BIT(INT_VID_FIFO_ERROR), BIT(INT_VID_FIFO_ERROR));
> mutex_unlock(&it6505->aux_lock);
>
> return state;
>
> --
> 2.34.1
>
>
--
With best wishes
Dmitry
