Re: [PATCH 2/3] drm/i915/tgl: Implement Wa_1604555607

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 26/07/2019 14:20, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-07-26 14:15:51)
>>
>> On 26/07/2019 01:10, Chris Wilson wrote:
>>> Quoting Lucas De Marchi (2019-07-26 01:02:25)
>>>> From: Michel Thierry <michel.thierry@intel.com>
>>>>
>>>> Implement Wa_1604555607 (set the DS pairing timer to 128 cycles).
>>>> FF_MODE2 is part of the register state context, that's why it is
>>>> implemented here.
>>>>
>>>> Signed-off-by: Michel Thierry <michel.thierry@intel.com>
>>>> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
>>>> ---
>>>>    drivers/gpu/drm/i915/gt/intel_workarounds.c | 7 +++++++
>>>>    drivers/gpu/drm/i915/i915_reg.h             | 5 +++++
>>>>    2 files changed, 12 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
>>>> index a6eb9c6e87ec..3235ef355dfd 100644
>>>> --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
>>>> +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
>>>> @@ -572,6 +572,13 @@ static void icl_ctx_workarounds_init(struct intel_engine_cs *engine,
>>>>    static void tgl_ctx_workarounds_init(struct intel_engine_cs *engine,
>>>>                                        struct i915_wa_list *wal)
>>>>    {
>>>> +       u32 val;
>>>> +
>>>> +       /* Wa_1604555607:tgl */
>>>> +       val = intel_uncore_read(engine->uncore, FF_MODE2);
>>>> +       val &= ~FF_MODE2_TDS_TIMER_MASK;
>>>> +       val |= FF_MODE2_TDS_TIMER_128;
>>>> +       wa_write_masked_or(wal, FF_MODE2, FF_MODE2_TDS_TIMER_MASK, val);
>>>
>>> It will do a rmw on application, so you just need
>>>        wa_write_masked_or(wal, FF_MODE2,
>>>                           FF_MODE2_TDS_TIMER_MASK, FF_MODE2_TDS_TIMER_128);
>>
>> Not with ctx was unfortunately, no rmw there, just lri.
> 
> Odd that we read from outside the ctx then, no?

Perhaps. We have to get the default value from somewhere. There is one 
like this already, GEN8_L3CNTLREG, from not too long ago.

> We can do rmw inside ctx_wa if we have to thanks to MI_MATH. Should we
> start preparing for that nightmare? :)

When you say preparing it makes it sounds complicated so I want to say 
no. But sure, if you have extra time go for it.

Regards,

Tvrtko
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