Re: [PATCH] drm/i915/skl: While sanitizing cdclock check the SWF18 as well

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

On 11/2/2015 6:49 PM, Kumar, Shobhit wrote:
> On 11/02/2015 06:40 PM, Jani Nikula wrote:
>> On Mon, 02 Nov 2015, Shobhit Kumar <shobhit.kumar@intel.com> wrote:
>>> SWF18 is set if the display has been intialized by the pre-os. It
>>> also gives what configuration is enabled on which pipe. The DPLL and
>>> CDCLK verification checks can fail as the pre-os does initialize the
>>> DPLL for Audio codec initialization. So fisrt check if SWF18 is set and
>>> then follow through with other DPLL and CDCLK verification.
>>
>> Can we universally trust all bios/gop/bootloader/whatnot to have
>> initialized this? What if it's not set?
>>
>
> As per my discussion with gop team, this has been enabled in main 
> stream for quite sometime including VLV, CHT, BDW, SKL+ and is common 
> for GOP/VBIOS across chrome/windows/android. So yes I think we can 
> universally trust as of now.
This has been added since IVB timeframe and should be part of VBT spec. 
but i just encountered
an issue in Android Charging OS where there is no modeset and is using 
the displays
enabled by GOP/VBIOS. This patch might break such expectations.
>
> Regards
> Shobhit
>
>> BR,
>> Jani.
>>
>>
>>
>>>
>>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
>>> ---
>>>   drivers/gpu/drm/i915/i915_reg.h      | 3 +++
>>>   drivers/gpu/drm/i915/intel_display.c | 8 ++++++++
>>>   2 files changed, 11 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_reg.h 
>>> b/drivers/gpu/drm/i915/i915_reg.h
>>> index 9ee9481..bd476ff 100644
>>> --- a/drivers/gpu/drm/i915/i915_reg.h
>>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>>> @@ -5006,6 +5006,9 @@ enum skl_disp_power_wells {
>>>   #define SWF1(i)    (dev_priv->info.display_mmio_offset + 0x71410 + 
>>> (i) * 4)
>>>   #define SWF3(i)    (dev_priv->info.display_mmio_offset + 0x72414 + 
>>> (i) * 4)
>>>
>>> +/* VBIOS flag for display initialized status */
>>> +#define GEN6_SWF18  (dev_priv->info.display_mmio_offset + 0x4F060)
>>> +
>>>   /* Pipe B */
>>>   #define _PIPEBDSL (dev_priv->info.display_mmio_offset + 0x71000)
>>>   #define _PIPEBCONF (dev_priv->info.display_mmio_offset + 0x71008)
>>> diff --git a/drivers/gpu/drm/i915/intel_display.c 
>>> b/drivers/gpu/drm/i915/intel_display.c
>>> index 103cacb..0ecb35c 100644
>>> --- a/drivers/gpu/drm/i915/intel_display.c
>>> +++ b/drivers/gpu/drm/i915/intel_display.c
>>> @@ -5761,6 +5761,14 @@ int skl_sanitize_cdclk(struct 
>>> drm_i915_private *dev_priv)
>>>       uint32_t cdctl = I915_READ(CDCLK_CTL);
>>>       int freq = dev_priv->skl_boot_cdclk;
>>>
>>> +    /*
>>> +     * check if the pre-os intialized the display
>>> +     * There is SWF18 scratchpad register defined which is set by the
>>> +     * pre-os which can be used by the OS drivers to check the status
>>> +     */
>>> +    if ((I915_READ(GEN6_SWF18) & 0x00FFFF) == 0)
>>> +        goto sanitize;
>>> +
>>>       /* Is PLL enabled and locked ? */
>>>       if (!((lcpll1 & LCPLL_PLL_ENABLE) && (lcpll1 & LCPLL_PLL_LOCK)))
>>>           goto sanitize;
>>
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