"drm/i915: Use the correct crtc when sanitizing plane mapping" seems to cause the readback plane state to always be 0

"drm/i915: Use the correct crtc when sanitizing plane mapping" seems to cause the readback plane state to always be 0

[Hans de Goede]

Hi Ville,

While debugging the briefly purple screen on DSI panels issue for
which I just send a revert, I also noticed something odd with
your commit 9b27390139db ("drm/i915: Use the correct crtc when
sanitizing plane mapping").

When comparing drm.debug=0x1e logs between 4.19 and 4.20-rc1
I noticed that this bit of the initial hw state readback logging
in 4.19:

[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1

Changed to:

[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
[drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0

In 4.20-rc1 (the other pipes are off and report 0 active planes
in both cases).

At first I thought that this was the cause of the purple flicker,
but it wasn't and I'm not seeing any negative side-effects of this
(AFAICT).

Still this seems like a bug to me where the state read-back now no
longer detects the active primary plane on pipe B. This is on a
Cherry Trail device with a DSI panel.

I can confirm that reverting commit 9b27390139db ("drm/i915: Use
the correct crtc when sanitizing plane mapping") makes the
log messages the same as they were in 4.19 again.

Regards,

Hans
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Re: "drm/i915: Use the correct crtc when sanitizing plane mapping" seems to cause the readback plane state to always be 0

[Ville Syrjälä]

On Mon, Nov 19, 2018 at 11:47:00PM +0100, Hans de Goede wrote:
> Hi Ville,
> 
> While debugging the briefly purple screen on DSI panels issue for
> which I just send a revert, I also noticed something odd with
> your commit 9b27390139db ("drm/i915: Use the correct crtc when
> sanitizing plane mapping").
> 
> When comparing drm.debug=0x1e logs between 4.19 and 4.20-rc1
> I noticed that this bit of the initial hw state readback logging
> in 4.19:
> 
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
> 
> Changed to:
> 
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0

That debug message is just garbage now. I removed it in the following
commit.

-- 
Ville Syrjälä
Intel
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Re: "drm/i915: Use the correct crtc when sanitizing plane mapping" seems to cause the readback plane state to always be 0

[Hans de Goede]

Hi,

On 20-11-18 12:28, Ville Syrjälä wrote:
> On Mon, Nov 19, 2018 at 11:47:00PM +0100, Hans de Goede wrote:
>> Hi Ville,
>>
>> While debugging the briefly purple screen on DSI panels issue for
>> which I just send a revert, I also noticed something odd with
>> your commit 9b27390139db ("drm/i915: Use the correct crtc when
>> sanitizing plane mapping").
>>
>> When comparing drm.debug=0x1e logs between 4.19 and 4.20-rc1
>> I noticed that this bit of the initial hw state readback logging
>> in 4.19:
>>
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x1
>>
>> Changed to:
>>
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
>> [drm:intel_modeset_setup_hw_state [i915]] pipe B active planes 0x0
> 
> That debug message is just garbage now. I removed it in the following
> commit.

Ah, ok. Thank you for explaining this.

Regards,

Hans

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