[PATCH v2 1/5] drm/bridge: it6505: fix link training state HW register reset

[Dmitry Baryshkov]

On Wed, Mar 26, 2025 at 01:34:13PM +0800, Hermes Wu via B4 Relay wrote:
> From: Hermes Wu <Hermes.wu at ite.com.tw>
> 
> In order to reset HW link auto training state,
> bits FORCE_RETRAIN and MANUAL_TRAIN at REG_TRAIN_CTRL1 must be set
> at the same time.

Nit: please start by describing the problem that the patch attempts to
solve.

> 
> Signed-off-by: Hermes Wu <Hermes.wu at ite.com.tw>
> ---
>  drivers/gpu/drm/bridge/ite-it6505.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
> index 88ef76a37fe6accacdd343839ff2569b31b18ceb..b47042dc06bb1e1dfd92bc0dc6d69dc918a140ba 100644
> --- a/drivers/gpu/drm/bridge/ite-it6505.c
> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> @@ -1806,7 +1806,9 @@ static bool it6505_link_start_auto_train(struct it6505 *it6505)
>  	mutex_lock(&it6505->aux_lock);
>  	it6505_set_bits(it6505, REG_TRAIN_CTRL0,
>  			FORCE_CR_DONE | FORCE_EQ_DONE, 0x00);
> -	it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
> +	/* reset link state machine and re start training*/
> +	it6505_write(it6505, REG_TRAIN_CTRL1,
> +		     FORCE_RETRAIN | MANUAL_TRAIN);
>  	it6505_write(it6505, REG_TRAIN_CTRL1, AUTO_TRAIN);
>  
>  	while (timeout > 0) {
> @@ -2377,7 +2379,7 @@ static void it6505_stop_link_train(struct it6505 *it6505)
>  {
>  	it6505->link_state = LINK_IDLE;
>  	cancel_work_sync(&it6505->link_works);
> -	it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN);
> +	it6505_write(it6505, REG_TRAIN_CTRL1, FORCE_RETRAIN | MANUAL_TRAIN);
>  }
>  
>  static void it6505_link_train_ok(struct it6505 *it6505)
> 
> -- 
> 2.34.1
> 
> 

-- 
With best wishes
Dmitry