Re: [PATCH 5/9] drm/i915: Clear out DPLL state from pipe config in DSI get config

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jul 10, 2015 at 05:37:07PM +0530, Sivakumar Thulasimani wrote:
> 
> 
> On 7/1/2015 6:12 PM, Daniel Vetter wrote:
> >On Tue, Jun 30, 2015 at 02:50:33PM +0300, Ville Syrjälä wrote:
> >>On Tue, Jun 30, 2015 at 12:13:37PM +0200, Daniel Vetter wrote:
> >>>On Mon, Jun 29, 2015 at 08:08:27PM +0300, Ville Syrjälä wrote:
> >>>>On Mon, Jun 29, 2015 at 07:56:05PM +0300, Ville Syrjälä wrote:
> >>>>>On Mon, Jun 29, 2015 at 06:42:11PM +0200, Daniel Vetter wrote:
> >>>>>>On Mon, Jun 29, 2015 at 03:25:52PM +0300, ville.syrjala@linux.intel.com wrote:
> >>>>>>>From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>>>>>>
> >>>>>>>VLV/CHV don't use the DPLL with DSI, so just clear out the DPLL state
> >>>>>>>from the pipe_config in intel_dsi_get_config(). This avoids spurious
> >>>>>>>state checker warnings. We already did it this way for DPLL_MD, but do
> >>>>>>>it for DPLL too.
> >>>>>>>
> >>>>>>>Toss in a WARN to intel_dsi_pre_enable() to make sure the ref clocks
> >>>>>>>are enabled however. Supposedly they have some meaning to DSI too.
> >>>>>>>We now keep the ref clocks always enabled while the disp2d well is
> >>>>>>>enabled.
> >>>>>>>
> >>>>>>>Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>>>>>>---
> >>>>>>>  drivers/gpu/drm/i915/intel_dsi.c | 15 +++++----------
> >>>>>>>  1 file changed, 5 insertions(+), 10 deletions(-)
> >>>>>>>
> >>>>>>>diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> >>>>>>>index 36e2148..92bb252 100644
> >>>>>>>--- a/drivers/gpu/drm/i915/intel_dsi.c
> >>>>>>>+++ b/drivers/gpu/drm/i915/intel_dsi.c
> >>>>>>>@@ -421,18 +421,12 @@ static void intel_dsi_pre_enable(struct intel_encoder *encoder)
> >>>>>>>  	/* Disable DPOunit clock gating, can stall pipe
> >>>>>>>  	 * and we need DPLL REFA always enabled */
> >>>>>>>-	tmp = I915_READ(DPLL(pipe));
> >>>>>>>-	tmp |= DPLL_REF_CLK_ENABLE_VLV;
> >>>>>>>-	I915_WRITE(DPLL(pipe), tmp);
> >>>>>>>-
> >>>>>>>-	/* update the hw state for DPLL */
> >>>>>>>-	intel_crtc->config->dpll_hw_state.dpll = DPLL_INTEGRATED_REF_CLK_VLV |
> >>>>>>>-		DPLL_REF_CLK_ENABLE_VLV | DPLL_VGA_MODE_DIS;
> >>>>>>>-
> >>>>>>>  	tmp = I915_READ(DSPCLK_GATE_D);
> >>>>>>>  	tmp |= DPOUNIT_CLOCK_GATE_DISABLE;
> >>>>>>>  	I915_WRITE(DSPCLK_GATE_D, tmp);
> >>>>>>>+	WARN_ON((I915_READ(DPLL(pipe)) & DPLL_REF_CLK_ENABLE_VLV) == 0);
> >>>>>>>+
> >>>>>>>  	/* put device in ready state */
> >>>>>>>  	intel_dsi_device_ready(encoder);
> >>>>>>>@@ -635,9 +629,10 @@ static void intel_dsi_get_config(struct intel_encoder *encoder,
> >>>>>>>  	DRM_DEBUG_KMS("\n");
> >>>>>>>  	/*
> >>>>>>>-	 * DPLL_MD is not used in case of DSI, reading will get some default value
> >>>>>>>-	 * set dpll_md = 0
> >>>>>>>+	 * DPLL is not used in case of DSI, reading will getsome default value.
> >>>>>>>+	 * Clear the state to keep the state checker happy.
> >>>>>>>  	 */
> >>>>>>>+	pipe_config->dpll_hw_state.dpll = 0;
> >>>>>>>  	pipe_config->dpll_hw_state.dpll_md = 0;
> >>>>>>State configs are supposed to be kzallocated. Needing this indicates a
> >>>>>>pretty serious bug - I'd vote to instead also ditch the dpll_md line and
> >>>>>>fix the offender.
> >>>>>There is no offender really. We read out the DPLL state before we know
> >>>>>which ports are active and hence can't tell at that point if the
> >>>>>information is really relevant.
> >>>So the bios leaves the DPLL enabled even when using a DSI port? Or do we
> >>>miss to check some routing bits in get_clock?
> >>Not necessarily enabled, but there are other bits in there that could be
> >>left in any state basically. The DSI port simply doesn't care.
> >If the enable bit is what's gating things here then we should just forgo
> >reading out any dpll register state if that's not set. Looking at the
> >vlv/chv state readout code that seems to be the trouble - there's nothing
> >guarding the register reads into the pipe_config at all. Didn't matter
> >pre-vlv without dsi since enable pipe should imply enabled dpll, but
> >obviously won't work correctly with dsi. Can you please spin such a patch
> >and remove the hacks here from dsi_get_config?
> >-Daniel
> Not sure i understand the point of contention here, just noticed this after
> i gave my RB :)
> so my justification on why this is proper is that DSI is not supposed to
> touch DPLL register
> any place we access dpll_hw_state.dpll is under !is_dsi check so that
> ensures that we dont
> program DPLL register for dsi panel. it was wrong to have originally modfied
> DPLL register
> inside intel_dsi_pre_enable so removal is fine. setting it to zero in
> intel_dsi_get_config
> is of no impact since any place we write back the contents of dpll_hw_state
> is past the
> !is_dsi check is never consumed by anyone as long as the CRTC uses DSI.

Ok, let's try a patch. Does the below work y/n? I've merged the patches up
to this one to dinq meanwhile, but I'd really like to close this first. If
it works I can rebase this patch here myself. Diff below is based on
-nightly with the above patch, so if you want to test on top of it you
also have to remove the dpll = 0; line too ofc.

Thanks, Daniel

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a7482ab140e1..c770655f5612 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8079,6 +8079,10 @@ static bool i9xx_get_pipe_config(struct intel_crtc *crtc,
 
 	i9xx_get_pfit_config(crtc, pipe_config);
 
+	tmp = I915_READ(DPLL(crtc->pipe));
+	if (!(tmp & DPLL_VCO_ENABLE))
+		return true;
+
 	if (INTEL_INFO(dev)->gen >= 4) {
 		tmp = I915_READ(DPLL_MD(crtc->pipe));
 		pipe_config->pixel_multiplier =
diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index f4438eb5b458..116b06632cb0 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -621,12 +621,6 @@ static void intel_dsi_get_config(struct intel_encoder *encoder,
 	u32 pclk;
 	DRM_DEBUG_KMS("\n");
 
-	/*
-	 * DPLL_MD is not used in case of DSI, reading will get some default value
-	 * set dpll_md = 0
-	 */
-	pipe_config->dpll_hw_state.dpll_md = 0;
-
 	pclk = vlv_get_dsi_pclk(encoder, pipe_config->pipe_bpp);
 	if (!pclk)
 		return;
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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