Re: [PATCH v2 8/9] drm/i915/dp: Improve intel_dp_aux_is_busy()

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Wed, 2018-04-18 at 15:43 -0700, José Roberto de Souza wrote:
> - Doing earlier return when not busy
> - using u32 instead of uint32_t
> - counting from 3 to 0 as it is is the most common in the driver
Hmm. I see more instances that increment the loop variable than the
opposite.

> - using DRM_WARN() instead of WARN()
Why? WARN and WARN_ON's are common afaict

> - adding aux port name to the debug message
Sounds like a good idea.

> - nuking last_status, it is one static variable to all DP ports
> also 2 different aux transactions with the same message size would
> have the same ch_ctl value, if really desired to reduce the number
> of debug messages it should be implemented a per aux ch last_status
Makes sense to do this.

> - no need to sleep in the last try
> - sleeping for 1 aux ch transaction time
Was this determined based on the clock speed or is it in the spec? I
see numbers for timeout, nothing for the transaction itself.


This patch mixes up functional changes with non-functional ones. I'd
prefer you split these changes.


> 
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> ---
> 
> New patch in this series.
> 
>  drivers/gpu/drm/i915/intel_dp.c | 23 ++++++++---------------
>  1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index a11465c62950..258e23961456 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1068,28 +1068,21 @@ static bool intel_dp_aux_is_busy(struct
> intel_dp *intel_dp)
>  	struct drm_i915_private *dev_priv =
>  			to_i915(intel_dig_port->base.base.dev);
>  	i915_reg_t ch_ctl;
> -	uint32_t status;
> -	int try;
> +	u32 status;
> +	unsigned int try;
>  
>  	ch_ctl = intel_dp->aux_ch_ctl_reg(intel_dp);
>  
> -	for (try = 0; try < 3; try++) {
> +	for (try = 3; try; try--) {
>  		status = I915_READ_NOTRACE(ch_ctl);
>  		if ((status & DP_AUX_CH_CTL_SEND_BUSY) == 0)
> -			break;
> -		msleep(1);
> +			return false;
> +		if (try > 1)
> +			usleep_range(400, 500);
>  	}
>  
> -	if (try == 3) {
> -		static u32 last_status = -1;
> -		const u32 status = I915_READ(ch_ctl);
> -
> -		if (status != last_status) {
> -			WARN(1, "dp_aux_ch not started status
> 0x%08x\n",
> -			     status);
> -			last_status = status;
> -		}
> -	}
> +	DRM_WARN("DP aux %c is busy 0x%08x\n",
> +		 aux_ch_name(intel_dp->aux_ch), status);
>  
>  	return true;
>  }
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx