Re: [PATCH 4/4] drm/i915: fix link rates reported for SKL

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On 8/17/2015 6:11 PM, Ville Syrjälä wrote:
On Mon, Aug 17, 2015 at 05:45:11PM +0530, Sivakumar Thulasimani wrote:
From: "Thulasimani,Sivakumar" <sivakumar.thulasimani@xxxxxxxxx>

This patch fixes the bug that SKL SKUs before B0 might return
HBR2 as supported even though it is not supposed to be enabled
on such platforms.

Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@xxxxxxxxx>
---
  drivers/gpu/drm/i915/intel_dp.c |   14 ++++++++------
  1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 03523b3..963fdae 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1224,21 +1224,23 @@ static bool intel_dp_is_hbr2_supported(struct drm_device *dev)
  static int
  intel_dp_source_rates(struct drm_device *dev, const int **source_rates)
  {
+	int size = 0;
  	if (IS_BROXTON(dev)) {
  		*source_rates = bxt_rates;
-		return ARRAY_SIZE(bxt_rates);
+		size = ARRAY_SIZE(bxt_rates);
  	} else if (IS_SKYLAKE(dev)) {
  		*source_rates = skl_rates;
-		return ARRAY_SIZE(skl_rates);
+		size = ARRAY_SIZE(skl_rates);
+	} else {
+		*source_rates = default_rates;
+		size = ARRAY_SIZE(default_rates);
  	}
- *source_rates = default_rates;
-
  	/* This depends on the fact that 5.4 is last value in the array */
  	if (intel_dp_is_hbr2_supported(dev))
-		return (DP_LINK_BW_5_4 >> 3) + 1;
+		return size;
  	else
-		return (DP_LINK_BW_2_7 >> 3) + 1;
+		return size - 1;
Maybe we should use rate_to_index() here? Should be a bit more
future proof for when we get HBR3. So, perhaps something like this?

{
	...
		*source_rates = bxt_rates;
		size_rates = ARRAY_SIZE(bxt_rates);
	...

	if (intel_dp_is_hbr2_supported)
		max_rate = 540000;
	else
		max_rate = 270000;

	size = rate_to_index(max_rate, *source_rates) + 1;
	if (WARN_ON(size > size_rates))
		size = size_rates;

	return size;
}

But that could be a followup patch.

Otherwise the series looks good so:
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
thanks for the review :)
  }
static void
--
1.7.9.5

--
regards,
Sivakumar

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