Re: [PATCH 4/5] drm/i915: Use ilk_wm_max_level() in latency debugfs files

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, May 13, 2014 at 03:30:27PM +0100, Damien Lespiau wrote:
> Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 18b3565..6801987 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -3084,7 +3084,7 @@ static const struct file_operations i915_display_crc_ctl_fops = {
>  static void wm_latency_show(struct seq_file *m, const uint16_t wm[5])
>  {
>  	struct drm_device *dev = m->private;
> -	int num_levels = IS_HASWELL(dev) || IS_BROADWELL(dev) ? 5 : 4;
> +	int num_levels = ilk_wm_max_level(dev) + 1;
>  	int level;
>  
>  	drm_modeset_lock_all(dev);
> @@ -3167,7 +3167,7 @@ static ssize_t wm_latency_write(struct file *file, const char __user *ubuf,
>  	struct seq_file *m = file->private_data;
>  	struct drm_device *dev = m->private;
>  	uint16_t new[5] = { 0 };
> -	int num_levels = IS_HASWELL(dev) || IS_BROADWELL(dev) ? 5 : 4;
> +	int num_levels = ilk_wm_max_level(dev) + 1;

One idea that has been rattling in my head would be to introduce
dev_priv->wm.max_level or some such thing that would be computed
dynamically like so:
dev_priv->wm.max_level = min(hw_max, last_level_with_valid_latency_value);

This way we could actually disable some of the deeper levels without
worrying that the watermark code will encounter a zero latency value
somewhere. We could even do other crazy things like trying out LP3
on ILK ;)

But that's a bit orthogonal, and even then this patch does make sense.

For patches 3-5:
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

I'll let someone else bikeshed the for_each_crtc macros.

>  	int level;
>  	int ret;
>  	char tmp[32];
> -- 
> 1.8.3.1
> 
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-- 
Ville Syrjälä
Intel OTC