Re: [PATCH] drm/i915/display: Implement wa_14024400148

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 15 Apr 2025, Nemesa Garg <nemesa.garg@intel.com> wrote:
> Workaround recommend use polling method
> for pm_demand to finish as to avoid timeout.
>
> Signed-off-by: Nemesa Garg <nemesa.garg@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_pmdemand.c | 27 +++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_pmdemand.c b/drivers/gpu/drm/i915/display/intel_pmdemand.c
> index d22b5469672d..610d05b73b99 100644
> --- a/drivers/gpu/drm/i915/display/intel_pmdemand.c
> +++ b/drivers/gpu/drm/i915/display/intel_pmdemand.c
> @@ -478,6 +478,22 @@ static bool intel_pmdemand_req_complete(struct intel_display *display)
>  		 XELPDP_PMDEMAND_REQ_ENABLE);
>  }
>  
> +static void intel_pmdemand_poll(struct intel_display *display)
> +{
> +	const unsigned int timeout_ms = 10;
> +	u32 status;
> +	int ret;
> +
> +	ret = intel_de_wait_custom(display, XELPDP_INITIATE_PMDEMAND_REQUEST(1),
> +				   XELPDP_PMDEMAND_REQ_ENABLE, 0,
> +				   50, timeout_ms, &status);
> +
> +	if (ret == -ETIMEDOUT)
> +		drm_err(display->drm,
> +			"timeout within %ums (status 0x%08x)\n",
> +			timeout_ms, status);

Imagine seeing "timeout within 10ms" in dmesg.

Timeout of what? 

> +}
> +
>  static void intel_pmdemand_wait(struct intel_display *display)
>  {
>  	if (!wait_event_timeout(display->pmdemand.waitqueue,
> @@ -508,7 +524,11 @@ void intel_pmdemand_program_dbuf(struct intel_display *display,
>  	intel_de_rmw(display, XELPDP_INITIATE_PMDEMAND_REQUEST(1), 0,
>  		     XELPDP_PMDEMAND_REQ_ENABLE);
>  
> -	intel_pmdemand_wait(display);
> +	/* Wa_14024400148 For lnl use polling method */
> +	if (DISPLAY_VER(display) == 20)
> +		intel_pmdemand_poll(display);
> +	else
> +		intel_pmdemand_wait(display);

Please just hide this within intel_pmdemand_wait() instead of
duplicating it everywhere.

>  
>  unlock:
>  	mutex_unlock(&display->pmdemand.lock);
> @@ -617,7 +637,10 @@ intel_pmdemand_program_params(struct intel_display *display,
>  	intel_de_rmw(display, XELPDP_INITIATE_PMDEMAND_REQUEST(1), 0,
>  		     XELPDP_PMDEMAND_REQ_ENABLE);
>  
> -	intel_pmdemand_wait(display);
> +	if (DISPLAY_VER(display) == 20)
> +		intel_pmdemand_poll(display);
> +	else
> +		intel_pmdemand_wait(display);
>  
>  unlock:
>  	mutex_unlock(&display->pmdemand.lock);

-- 
Jani Nikula, Intel