Re: [PATCH 13/20] drm/i915/dp: use generic poll_timeout_us() instead of wait_for() in link training

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Thu, 2025-08-28 at 15:20 +0300, Jani Nikula wrote:
> Prefer generic poll helpers over i915 custom helpers.
> 
> The functional change is losing the exponentially growing sleep of
> wait_for(), which used to be 10, 20, 40, ..., 640, and 1280 us.
> 
> Use an arbitrary constant 500 us sleep instead. The timeout remains
> at
> 500 ms.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>

> ---
>  .../drm/i915/display/intel_dp_link_training.c   | 17 +++++++++++++--
> --
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> index 9d14b4e59545..27f3716bdc1f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -22,6 +22,7 @@
>   */
>  
>  #include <linux/debugfs.h>
> +#include <linux/iopoll.h>
>  
>  #include <drm/display/drm_dp_helper.h>
>  #include <drm/drm_print.h>
> @@ -1135,15 +1136,19 @@ void intel_dp_stop_link_train(struct intel_dp
> *intel_dp,
>  {
>  	struct intel_display *display = to_intel_display(intel_dp);
>  	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)-
> >base;
> +	int ret;
>  
>  	intel_dp->link.active = true;
>  
>  	intel_dp_program_link_training_pattern(intel_dp, crtc_state,
> DP_PHY_DPRX,
>  					      
> DP_TRAINING_PATTERN_DISABLE);
>  
> -	if (intel_dp_is_uhbr(crtc_state) &&
> -	    wait_for(intel_dp_128b132b_intra_hop(intel_dp,
> crtc_state) == 0, 500)) {
> -		lt_dbg(intel_dp, DP_PHY_DPRX, "128b/132b intra-hop
> not clearing\n");
> +	if (intel_dp_is_uhbr(crtc_state)) {
> +		ret = poll_timeout_us(ret =
> intel_dp_128b132b_intra_hop(intel_dp, crtc_state),
> +				      ret == 0,
> +				      500, 500 * 1000, false);
> +		if (ret)
> +			lt_dbg(intel_dp, DP_PHY_DPRX, "128b/132b
> intra-hop not clearing\n");
>  	}
>  
>  	intel_hpd_unblock(encoder);
> @@ -1581,8 +1586,12 @@ intel_dp_128b132b_link_train(struct intel_dp
> *intel_dp,
>  			     int lttpr_count)
>  {
>  	bool passed = false;
> +	int ret;
>  
> -	if (wait_for(intel_dp_128b132b_intra_hop(intel_dp,
> crtc_state) == 0, 500)) {
> +	ret = poll_timeout_us(ret =
> intel_dp_128b132b_intra_hop(intel_dp, crtc_state),
> +			      ret == 0,
> +			      500, 500 * 1000, false);
> +	if (ret) {
>  		lt_err(intel_dp, DP_PHY_DPRX, "128b/132b intra-hop
> not clear\n");
>  		goto out;
>  	}