[Intel-gfx] [PATCH 10/15] drm/i915: Sprinkle a few missing locks around shared DDI clock registers

[Lucas De Marchi]

On Mon, Feb 01, 2021 at 08:33:38PM +0200, Ville Syrjälä wrote:
>From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
>The current code attempts to protect the RMWs into global
>clock routing registers with a mutex, but forgets to do so
>in a few places. Let's remedy that.

Forgets or doesn't do on purpose? In the first patches in this series I
was actually wondering why do we even have to take the lock you were
adding for some platforms.

>
>Note that at the moment we serialize all modesets onto single
>wq, so this shouldn't actually matter. But maybe one day we
>wish to attempt parallel modesets again...

and this answers that. But why don't we just stop getting the lock and
reintroduce them if/when we attempt parallel modeset?

Lucas De Marchi

>
>Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>---
> drivers/gpu/drm/i915/display/intel_ddi.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
>diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
>index 7137929f58bd..93552f3c2c43 100644
>--- a/drivers/gpu/drm/i915/display/intel_ddi.c
>+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
>@@ -3463,8 +3463,12 @@ static void cnl_ddi_disable_clock(struct intel_encoder *encoder)
> 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> 	enum port port = encoder->port;
>
>+	mutex_lock(&dev_priv->dpll.lock);
>+
> 	intel_de_rmw(dev_priv, DPCLKA_CFGCR0,
> 		     0, DPCLKA_CFGCR0_DDI_CLK_OFF(port));
>+
>+	mutex_unlock(&dev_priv->dpll.lock);
> }
>
> static void skl_ddi_enable_clock(struct intel_encoder *encoder,
>@@ -3493,8 +3497,12 @@ static void skl_ddi_disable_clock(struct intel_encoder *encoder)
> 	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
> 	enum port port = encoder->port;
>
>+	mutex_lock(&dev_priv->dpll.lock);
>+
> 	intel_de_rmw(dev_priv, DPLL_CTRL2,
> 		     0, DPLL_CTRL2_DDI_CLK_OFF(port));
>+
>+	mutex_unlock(&dev_priv->dpll.lock);
> }
>
> static void hsw_ddi_enable_clock(struct intel_encoder *encoder,
>-- 
>2.26.2
>
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