Re: [SKL-DMC-BUGFIX 3/5] drm/i915/skl: Do not disable cdclk PLL if csr firmware is present.

Daniel Vetter
2015-08-05T09:12:39Z

On Mon, Aug 03, 2015 at 09:55:34PM +0530, Animesh Manna wrote:
> While display engine entering into low power state no need to disable
> cdclk pll as CSR firmware of dmc will take care. If pll is already
> enabled firmware execution sequence will be blocked. This is one
> of the criteria for dmc to work properly.
>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Damien Lespiau <damien.lespiau@intel.com>
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Sunil Kamath <sunil.kamath@intel.com>
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> Signed-off-bt: Vathsala Nagaraju <vathsala.nagaraju@intel.com>
> Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>
> ---
> drivers/gpu/drm/i915/intel_display.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index af0bcfe..ef2ef4d 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5675,10 +5675,13 @@ void skl_uninit_cdclk(struct drm_i915_private *dev_priv)
> if (I915_READ(DBUF_CTL) & DBUF_POWER_STATE)
> DRM_ERROR("DBuf power disable timeout\n");
>
> - /* disable DPLL0 */
> - I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) & ~LCPLL_PLL_ENABLE);
> - if (wait_for(!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK), 1))
> - DRM_ERROR("Couldn't disable DPLL0\n");
> + if (dev_priv->csr.dmc_payload) {
> + /* disable DPLL0 */

Imo this needs a proper comment (and the current one is useless since it
just states exactly what the code does and is redundant). What about

/* DMC assumes ownership of LCPLL and will get confused if we
* touch it. */

instead before the if?
-Daniel

> + I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) &
> + ~LCPLL_PLL_ENABLE);
> + if (wait_for(!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK), 1))
> + DRM_ERROR("Couldn't disable DPLL0\n");
> + }
>
> intel_display_power_put(dev_priv, POWER_DOMAIN_PLLS);
> }
> --
> 2.0.2
>
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--
Daniel Vetter
Software Engineer, Intel Corporation