Re: [PATCH] drm/i915/bxt: Save/restore HOTPLUG_CTL during suspend/resume.

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

On 2/4/2016 7:29 AM, Thulasimani, Sivakumar wrote:
>
>
> On 2/4/2016 7:21 AM, Matt Roper wrote:
>> On Thu, Feb 04, 2016 at 07:17:08AM +0530, Thulasimani, Sivakumar wrote:
>>>
>>> On 2/4/2016 6:19 AM, Matt Roper wrote:
>>>> From: Bob Paauwe <bob.j.paauwe@intel.com>
>>>>
>>>> Broxton has some additional bits in the HOTPLUG_CTL register that
>>>> indicate whether the HPD sense lines need to be inverted or not for 
>>>> the
>>>> current platform.  The BIOS sets these bits to an appropriate value at
>>>> boot time, but the value is lost across suspend/resume.  We need to 
>>>> save
>>>> and restore the register so that hotplug and display detect works on
>>>> resume.
>>> i have a patch that is about to be upstreamed that will read and 
>>> write these
>>> values based on vbt. Shuhangi did the basic testing last week so will
>>> ask her to send to mail list today.  i would prefer that patch where
>>> we know how and when to set these bits rather than just save
>>> & restore.
>> Sure, sounds good.  Can your patch handle cases where there is no VBT by
>> falling back to a save/restore?  Quite often in the embedded world, we
>> have very specialized boot firmware that doesn't resemble vbios/gop and
>> doesn't have any VBT info.
>>
> hmm.. falling back will be required only when older VBTs are used. in 
> which case we
> assume that invert bit is not needed. if you still need this patch 
> then can you save
> and restore only the invert bits ? the code below does it for whole 
> register
> and might enable interrupts too which is not intention of the patch.
>
i am a bit more concerned on the scenario where there is no GOP/VBIOS
and so no VBT. can you share how common it is not have VBIOS/GOP ?
i am aware of coreboot but not sure if it has VBT or not (will check on 
this).
VBT is currently used in nightly where we have no other options
but whenever we dont have to depend on it we have some
sort if WA. i feel this is not good since we cannot say if some
scenario will work or not if VBT is not present. may be a new
thread just to discuss that ?

> regards,
> Sivakumar
>
>> Matt
>>
>>> regards,
>>> Sivakumar
>>>> Signed-off-by: Bob Paauwe <bob.j.paauwe@intel.com>
>>>> [mattrope: Expand commit message]
>>>> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/i915_drv.h     | 1 +
>>>>   drivers/gpu/drm/i915/i915_suspend.c | 7 +++++++
>>>>   2 files changed, 8 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h 
>>>> b/drivers/gpu/drm/i915/i915_drv.h
>>>> index 77227a3..2278117 100644
>>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>>> @@ -1061,6 +1061,7 @@ struct i915_suspend_saved_registers {
>>>>       uint64_t saveFENCE[I915_MAX_NUM_FENCES];
>>>>       u32 savePCH_PORT_HOTPLUG;
>>>>       u16 saveGCDGMBUS;
>>>> +    u32 saveHOTPLUG;
>>>>   };
>>>>   struct vlv_s0ix_state {
>>>> diff --git a/drivers/gpu/drm/i915/i915_suspend.c 
>>>> b/drivers/gpu/drm/i915/i915_suspend.c
>>>> index 34e061a..efe1e77 100644
>>>> --- a/drivers/gpu/drm/i915/i915_suspend.c
>>>> +++ b/drivers/gpu/drm/i915/i915_suspend.c
>>>> @@ -59,6 +59,10 @@ static void i915_save_display(struct drm_device 
>>>> *dev)
>>>>       /* save FBC interval */
>>>>       if (HAS_FBC(dev) && INTEL_INFO(dev)->gen <= 4 && !IS_G4X(dev))
>>>>           dev_priv->regfile.saveFBC_CONTROL = I915_READ(FBC_CONTROL);
>>>> +
>>>> +    if (IS_BROXTON(dev))
>>>> +        dev_priv->regfile.saveHOTPLUG = I915_READ(PCH_PORT_HOTPLUG);
>>>> +
>>>>   }
>>>>   static void i915_restore_display(struct drm_device *dev)
>>>> @@ -98,6 +102,9 @@ static void i915_restore_display(struct 
>>>> drm_device *dev)
>>>>       if (HAS_FBC(dev) && INTEL_INFO(dev)->gen <= 4 && !IS_G4X(dev))
>>>>           I915_WRITE(FBC_CONTROL, dev_priv->regfile.saveFBC_CONTROL);
>>>> +    if (IS_BROXTON(dev))
>>>> +        I915_WRITE(PCH_PORT_HOTPLUG, dev_priv->regfile.saveHOTPLUG);
>>>> +
>>>>       i915_redisable_vga(dev);
>>>>   }
>
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