Re: [Intel-gfx] [PATCH v4] drm/i915/ilk: Don't disable SSC source if it's in use

[Lyude Paul <cpaul@redhat.com>]

On Mon, 2016-06-06 at 14:30 +0300, Ville Syrjälä wrote:
> On Thu, May 26, 2016 at 09:54:56AM +0200, Daniel Vetter wrote:
> > 
> > On Wed, May 25, 2016 at 02:11:02PM -0400, Lyude wrote:
> > > 
> > > Thanks to Ville Syrjälä for pointing me towards the cause of this issue.
> > > 
> > > Unfortunately one of the sideaffects of having the refclk for a DPLL set
> > > to SSC is that as long as it's set to SSC, the GPU will prevent us from
> > > powering down any of the pipes or transcoders using it. A couple of
> > > BIOSes enable SSC in both PCH_DREF_CONTROL and in the DPLL
> > > configurations. This causes issues on the first modeset, since we don't
> > > expect SSC to be left on and as a result, can't successfully power down
> > > the pipes or the transcoders using it. Here's an example from this Dell
> > > OptiPlex 990:
> > > 
> > > [drm:intel_modeset_init] SSC enabled by BIOS, overriding VBT which says
> > > disabled
> > > [drm:intel_modeset_init] 2 display pipes available.
> > > [drm:intel_update_cdclk] Current CD clock rate: 400000 kHz
> > > [drm:intel_update_max_cdclk] Max CD clock rate: 400000 kHz
> > > [drm:intel_update_max_cdclk] Max dotclock rate: 360000 kHz
> > > vgaarb: device changed decodes:
> > > PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
> > > [drm:intel_crt_reset] crt adpa set to 0xf40000
> > > [drm:intel_dp_init_connector] Adding DP connector on port C
> > > [drm:intel_dp_aux_init] registering DPDDC-C bus for card0-DP-1
> > > [drm:ironlake_init_pch_refclk] has_panel 0 has_lvds 0 has_ck505 0
> > > [drm:ironlake_init_pch_refclk] Disabling SSC entirely
> > > … later we try committing the first modeset …
> > > [drm:intel_dump_pipe_config] [CRTC:26][modeset] config ffff88041b02e800
> > > for pipe A
> > > [drm:intel_dump_pipe_config] cpu_transcoder: A
> > > …
> > > [drm:intel_dump_pipe_config] dpll_hw_state: dpll: 0xc4016001, dpll_md:
> > > 0x0, fp0: 0x20e08, fp1: 0x30d07
> > > [drm:intel_dump_pipe_config] planes on this crtc
> > > [drm:intel_dump_pipe_config] STANDARD PLANE:23 plane: 0.0 idx: 0 enabled
> > > [drm:intel_dump_pipe_config]     FB:42, fb = 800x600 format = 0x34325258
> > > [drm:intel_dump_pipe_config]     scaler:0 src (0, 0) 800x600 dst (0, 0)
> > > 800x600
> > > [drm:intel_dump_pipe_config] CURSOR PLANE:25 plane: 0.1 idx: 1 disabled,
> > > scaler_id = 0
> > > [drm:intel_dump_pipe_config] STANDARD PLANE:27 plane: 0.1 idx: 2 disabled,
> > > scaler_id = 0
> > > [drm:intel_get_shared_dpll] CRTC:26 allocated PCH DPLL A
> > > [drm:intel_get_shared_dpll] using PCH DPLL A for pipe A
> > > [drm:ilk_audio_codec_disable] Disable audio codec on port C, pipe A
> > > [drm:intel_disable_pipe] disabling pipe A
> > > ------------[ cut here ]------------
> > > WARNING: CPU: 1 PID: 130 at drivers/gpu/drm/i915/intel_display.c:1146
> > > intel_disable_pipe+0x297/0x2d0 [i915]
> > > pipe_off wait timed out
> > > …
> > > ---[ end trace 94fc8aa03ae139e8 ]---
> > > [drm:intel_dp_link_down]
> > > [drm:ironlake_crtc_disable [i915]] *ERROR* failed to disable transcoder A
> > > 
> > > Later modesets succeed since they reset the DPLL's configuration anyway,
> > > but this is enough to get stuck with a big fat warning in dmesg.
> > > 
> > > A better solution would be to add refcounts for the SSC source, but for
> > > now leaving the source clock on should suffice.
> > > 
> > > Changes since v3:
> > >  - Move temp variable into loop
> > >  - Move checks for using_ssc_source to after we've figured out has_ck505
> > >  - Add using_ssc_source to debug output
> > > Changes since v2:
> > >  - Fix debug output for when we disable the CPU source
> > > Changes since v1:
> > >  - Leave the SSC source clock on instead of just shutting it off on all
> > >    of the DPLL configurations.
> > > 
> > > Cc: stable@vger.kernel.org
> > > Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Signed-off-by: Lyude <cpaul@redhat.com>
> > Queued for -next, thanks for the patch.
> Looks like this one broke one of the ILKs in CI.
> 
> [   13.100979] [drm:ironlake_init_pch_refclk] has_panel 1 has_lvds 1 has_ck505
> 0 using_ssc_source 1
> [   13.101413] ------------[ cut here ]------------
> [   13.101429] kernel BUG at drivers/gpu/drm/i915/intel_display.c:8528!
> 
> which is the 'BUG_ON(val != final)' at the end of ironlake_init_pch_refclk().
> 
Managed to find a machine at the office here that I could reproduce this on and
figured out the problem with the patch. Unfortunately, the Optiplex 990 that I
was seeing this issue on already left the office and the person in charge of it
just went on PTO until the end of the week. For the time being don't merge this
patch until I can get access to that machine again and make sure the fixed
version of this patch still works on the 990. I'll send the new version once I'm
able to test it.

Cheers,
	Lyude

> 
> > 
> > -Daniel
> > 
> > > 
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c | 49 ++++++++++++++++++++++++++-----
> > > -----
> > >  1 file changed, 36 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > > b/drivers/gpu/drm/i915/intel_display.c
> > > index d500e6f..471e3a8 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -8230,12 +8230,14 @@ static void ironlake_init_pch_refclk(struct
> > > drm_device *dev)
> > >  {
> > >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > >  	struct intel_encoder *encoder;
> > > +	int i;
> > >  	u32 val, final;
> > >  	bool has_lvds = false;
> > >  	bool has_cpu_edp = false;
> > >  	bool has_panel = false;
> > >  	bool has_ck505 = false;
> > >  	bool can_ssc = false;
> > > +	bool using_ssc_source = false;
> > >  
> > >  	/* We need to take the global config into account */
> > >  	for_each_intel_encoder(dev, encoder) {
> > > @@ -8262,8 +8264,22 @@ static void ironlake_init_pch_refclk(struct
> > > drm_device *dev)
> > >  		can_ssc = true;
> > >  	}
> > >  
> > > -	DRM_DEBUG_KMS("has_panel %d has_lvds %d has_ck505 %d\n",
> > > -		      has_panel, has_lvds, has_ck505);
> > > +	/* Check if any DPLLs are using the SSC source */
> > > +	for (i = 0; i < dev_priv->num_shared_dpll; i++) {
> > > +		u32 temp = I915_READ(PCH_DPLL(i));
> > > +
> > > +		if (!(temp & DPLL_VCO_ENABLE))
> > > +			continue;
> > > +
> > > +		if ((temp & PLL_REF_INPUT_MASK) ==
> > > +		    PLLB_REF_INPUT_SPREADSPECTRUMIN) {
> > > +			using_ssc_source = true;
> > > +			break;
> > > +		}
> > > +	}
> > > +
> > > +	DRM_DEBUG_KMS("has_panel %d has_lvds %d has_ck505 %d
> > > using_ssc_source %d\n",
> > > +		      has_panel, has_lvds, has_ck505, using_ssc_source);
> > >  
> > >  	/* Ironlake: try to setup display ref clock before DPLL
> > >  	 * enabling. This is only under driver's control after
> > > @@ -8283,9 +8299,12 @@ static void ironlake_init_pch_refclk(struct
> > > drm_device *dev)
> > >  	else
> > >  		final |= DREF_NONSPREAD_SOURCE_ENABLE;
> > >  
> > > -	final &= ~DREF_SSC_SOURCE_MASK;
> > >  	final &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
> > > -	final &= ~DREF_SSC1_ENABLE;
> > > +
> > > +	if (!using_ssc_source) {
> > > +		final &= ~DREF_SSC_SOURCE_MASK;
> > > +		final &= ~DREF_SSC1_ENABLE;
> > > +	}
> > >  
> > >  	if (has_panel) {
> > >  		final |= DREF_SSC_SOURCE_ENABLE;
> > > @@ -8348,7 +8367,7 @@ static void ironlake_init_pch_refclk(struct
> > > drm_device *dev)
> > >  		POSTING_READ(PCH_DREF_CONTROL);
> > >  		udelay(200);
> > >  	} else {
> > > -		DRM_DEBUG_KMS("Disabling SSC entirely\n");
> > > +		DRM_DEBUG_KMS("Disabling CPU source output\n");
> > >  
> > >  		val &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
> > >  
> > > @@ -8359,16 +8378,20 @@ static void ironlake_init_pch_refclk(struct
> > > drm_device *dev)
> > >  		POSTING_READ(PCH_DREF_CONTROL);
> > >  		udelay(200);
> > >  
> > > -		/* Turn off the SSC source */
> > > -		val &= ~DREF_SSC_SOURCE_MASK;
> > > -		val |= DREF_SSC_SOURCE_DISABLE;
> > > +		if (!using_ssc_source) {
> > > +			DRM_DEBUG_KMS("Disabling SSC source\n");
> > >  
> > > -		/* Turn off SSC1 */
> > > -		val &= ~DREF_SSC1_ENABLE;
> > > +			/* Turn off the SSC source */
> > > +			val &= ~DREF_SSC_SOURCE_MASK;
> > > +			val |= DREF_SSC_SOURCE_DISABLE;
> > >  
> > > -		I915_WRITE(PCH_DREF_CONTROL, val);
> > > -		POSTING_READ(PCH_DREF_CONTROL);
> > > -		udelay(200);
> > > +			/* Turn off SSC1 */
> > > +			val &= ~DREF_SSC1_ENABLE;
> > > +
> > > +			I915_WRITE(PCH_DREF_CONTROL, val);
> > > +			POSTING_READ(PCH_DREF_CONTROL);
> > > +			udelay(200);
> > > +		}
> > >  	}
> > >  
> > >  	BUG_ON(val != final);
> > > -- 
> > > 2.5.5
> > > 
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > -- 
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch