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

[Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>]

On 7/13/2015 2:21 PM, Daniel Vetter wrote:
> 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;
i am fine with this patch.

-- 
regards,
Sivakumar

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