Re: [PATCH] drm/i915: Setting pch_id for Gen7.5+ in virtual environment

[Martin Peres <martin.peres@linux.intel.com>]

On 30/03/17 08:39, Zhang, Xiong Y wrote:
>> On Wed, Mar 29, 2017 at 05:02:47PM +0800, Xiong Zhang wrote:
>>> In a virtual passthrough environment, the ISA bridge isn't able to
>>> be passed through. So pch_id couldn't be gotten from ISA bridge, but
>>> pch_id is used to identify LPT_H and LPT_LP, this patch set pch_id
>>> according to IGD type.
>>>
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99938
>>>
>>> Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.com>
>>> ---
>>>  drivers/gpu/drm/i915/i915_drv.c | 8 ++++++++
>>>  1 file changed, 8 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_drv.c
>> b/drivers/gpu/drm/i915/i915_drv.c
>>> index 8b807a9..32a9bff 100644
>>> --- a/drivers/gpu/drm/i915/i915_drv.c
>>> +++ b/drivers/gpu/drm/i915/i915_drv.c
>>> @@ -135,9 +135,17 @@ static enum intel_pch intel_virt_detect_pch(struct
>> drm_i915_private *dev_priv)
>>>  		DRM_DEBUG_KMS("Assuming CouarPoint PCH\n");
>>>  	} else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
>>>  		ret = PCH_LPT;
>>> +		if (IS_HSW_ULT(dev_priv) || IS_BDW_ULT(dev_priv))
>>> +			dev_priv->pch_id = INTEL_PCH_LPT_LP_DEVICE_ID_TYPE;
>>> +		else
>>> +			dev_priv->pch_id = INTEL_PCH_LPT_DEVICE_ID_TYPE;
>>>  		DRM_DEBUG_KMS("Assuming LynxPoint PCH\n");
>>>  	} else if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv)) {
>>>  		ret = PCH_SPT;
>>> +		if (IS_SKL_ULT(dev_priv) || IS_KBL_ULT(dev_priv))
>>> +			dev_priv->pch_id = INTEL_PCH_SPT_LP_DEVICE_ID_TYPE;
>>> +		else
>>> +			dev_priv->pch_id = INTEL_PCH_SPT_DEVICE_ID_TYPE;
>>
>> I'm not 100% sure the ULT/ULX <=> LP thing always holds. I *think* it
>> should but I've never been able to convince myself totally.
> [Zhang, Xiong Y] For BDW ULT/ULX, it should be LP. A picture from https://gfxspecs.intel.com/Predator/Home/Index/4216 could confirm this.
> For HSW ULT/ULX, I couldn't find a material to confirm this.
> Anyway I copy this condition from the WARN_ON() in intel_detect_pch()
>
> For SKL/KBL ULT/ULX, I couldn't find a material to confirm this neither.
>
>> As far as KBL goes, maybe we want PCH_KBP for it? Although I don't actually
>> know why we even make the distinction between the two since they seem
>> identical for us, and we don't distinguish LPT vs. WPT either. Rodrigo?
> [Zhang, Xiong Y] For PCH_KBP, I couldn't find out which KBL type will co-work with it.
> As the real ISA Bridge doesn't exist in a emulated guest machine, we couldn't get the real and accurate pch_id in guest. In such passthrough virtual environment, the only real HW is IGD which is passed through to guest, we could only assume the pch_id from this IGD.
> Fortunately pch_id is only used to identify LPT_LP and LPT_H currently.
> Without this patch, pch_id is totally wrong. And on LPT_LP platform without this patch, the local HDMI/DP display couldn't lightup when guest boot up. But this patch could only remedy part of pch_id. Currently I have two plans to improve this patch:
> 1) only remain pch_id assuming for HSW and BDW, as this is really we need to fix the bug.
>   Delete pch_id assuming for SKL and KBL, as currently i915 driver don't use it.
> 2) Claim this patch's limitation in commit message.
> Any suggestion ?

Guys, any updates on this?

This blocks the testing of the following tests on fi-bdw-gvtdvm:
igt@drv_module_reload@basic-reload
igt@drv_module_reload@basic-reload-final
igt@drv_module_reload@basic-reload-inject
igt@gem_exec_suspend@basic-s3
igt@gem_exec_suspend@basic-s4-devices
igt@kms_pipe_crc_basic@suspend-read-crc-pipe-a
igt@kms_pipe_crc_basic@suspend-read-crc-pipe-b
igt@kms_pipe_crc_basic@suspend-read-crc-pipe-c

Thanks,
Martin
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