Re: [CI 2/2] drm/i915/perf: reuse intel_lrc ctx regs macro

[Lionel Landwerlin <lionel.g.landwerlin@intel.com>]

On 15/08/18 09:49, Tvrtko Ursulin wrote:
>
> On 14/08/2018 19:57, Chris Wilson wrote:
>> Quoting Tvrtko Ursulin (2018-08-14 19:49:46)
>>>
>>> On 13/08/2018 10:16, Chris Wilson wrote:
>>>> Quoting Tvrtko Ursulin (2018-08-13 10:11:44)
>>>>>
>>>>> On 13/08/2018 09:16, Chris Wilson wrote:
>>>>>> Quoting Tvrtko Ursulin (2018-08-13 09:02:18)
>>>>>>> From: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>>>>>>>
>>>>>>> Abstract the context image access a bit.
>>>>>>>
>>>>>>> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>>>>>>> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>>>>> ---
>>>>>>>     drivers/gpu/drm/i915/i915_perf.c | 34 
>>>>>>> +++++++++++++++-----------------
>>>>>>>     1 file changed, 16 insertions(+), 18 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/i915/i915_perf.c 
>>>>>>> b/drivers/gpu/drm/i915/i915_perf.c
>>>>>>> index 49597cf31707..ccb20230df2c 100644
>>>>>>> --- a/drivers/gpu/drm/i915/i915_perf.c
>>>>>>> +++ b/drivers/gpu/drm/i915/i915_perf.c
>>>>>>> @@ -210,6 +210,7 @@
>>>>>>>     #include "i915_oa_cflgt3.h"
>>>>>>>     #include "i915_oa_cnl.h"
>>>>>>>     #include "i915_oa_icl.h"
>>>>>>> +#include "intel_lrc_reg.h"
>>>>>>>         /* HW requires this to be a power of two, between 128k 
>>>>>>> and 16M, though driver
>>>>>>>      * is currently generally designed assuming the largest 16M 
>>>>>>> size is used such
>>>>>>> @@ -1636,27 +1637,25 @@ static void 
>>>>>>> gen8_update_reg_state_unlocked(struct i915_gem_context *ctx,
>>>>>>>            u32 ctx_oactxctrl = 
>>>>>>> dev_priv->perf.oa.ctx_oactxctrl_offset;
>>>>>>>            u32 ctx_flexeu0 = dev_priv->perf.oa.ctx_flexeu0_offset;
>>>>>>>            /* The MMIO offsets for Flex EU registers aren't 
>>>>>>> contiguous */
>>>>>>> -       u32 flex_mmio[] = {
>>>>>>> -               i915_mmio_reg_offset(EU_PERF_CNTL0),
>>>>>>> -               i915_mmio_reg_offset(EU_PERF_CNTL1),
>>>>>>> -               i915_mmio_reg_offset(EU_PERF_CNTL2),
>>>>>>> -               i915_mmio_reg_offset(EU_PERF_CNTL3),
>>>>>>> -               i915_mmio_reg_offset(EU_PERF_CNTL4),
>>>>>>> -               i915_mmio_reg_offset(EU_PERF_CNTL5),
>>>>>>> -               i915_mmio_reg_offset(EU_PERF_CNTL6),
>>>>>>> +       i915_reg_t flex_regs[] = {
>>>>>>> +               EU_PERF_CNTL0,
>>>>>>> +               EU_PERF_CNTL1,
>>>>>>> +               EU_PERF_CNTL2,
>>>>>>> +               EU_PERF_CNTL3,
>>>>>>> +               EU_PERF_CNTL4,
>>>>>>> +               EU_PERF_CNTL5,
>>>>>>> +               EU_PERF_CNTL6,
>>>>>>>            };
>>>>>>>            int i;
>>>>>>>     -       reg_state[ctx_oactxctrl] = 
>>>>>>> i915_mmio_reg_offset(GEN8_OACTXCONTROL);
>>>>>>> -       reg_state[ctx_oactxctrl+1] = 
>>>>>>> (dev_priv->perf.oa.period_exponent <<
>>>>>>> - GEN8_OA_TIMER_PERIOD_SHIFT) |
>>>>>>> - (dev_priv->perf.oa.periodic ?
>>>>>>> - GEN8_OA_TIMER_ENABLE : 0) |
>>>>>>> - GEN8_OA_COUNTER_RESUME;
>>>>>>> +       CTX_REG(reg_state, ctx_oactxctrl, GEN8_OACTXCONTROL,
>>>>>>> +               (dev_priv->perf.oa.period_exponent << 
>>>>>>> GEN8_OA_TIMER_PERIOD_SHIFT) |
>>>>>>> +               (dev_priv->perf.oa.periodic ? 
>>>>>>> GEN8_OA_TIMER_ENABLE : 0) |
>>>>>>> +               GEN8_OA_COUNTER_RESUME);
>>>>>>
>>>>>> I'll be honest but, I don't think it's CTX_REG() that helps 
>>>>>> improve the
>>>>>> readability here.
>>>>>>
>>>>>> The really odd part is that this sticks itself into a bare part 
>>>>>> of the
>>>>>> register state not surrounded by any LRI and after a BB_END. This
>>>>>> routine can only work for established contexts, it should not 
>>>>>> work for
>>>>>> execlists_init_reg_state.
>>>>>
>>>>> Unless I am missing something change is completely mechanical, so any
>>>>> question marks you have are already there, right? What do you 
>>>>> suggest is
>>>>> the action here?
>>>>
>>>> Sure, the only thing I question of this patch itself is whether
>>>> CTX_REG() is simply too much horrible obfuscating magic.
>>>
>>> Turn a blind eye if the perceived badness factor is below some
>>> threshold? Following patch depends on this one, so if I have to drop
>>> this one, then I have to rework the next one etc.. well, it's not the
>>> worst problem, so yeah, whatever. Make a call and let me know.
>>
>> The patch was fine, just worrying about the surrounding code.
>
> I misunderstood. So only about ctx_oactxctrl_offset and 
> ctx_flexeu0_offset from i915_perf.c? Maybe that is some OA magic, I 
> have not idea. CC-ing Lionel in case he can shed some light on it.

Those are the offsets at which the hardware will store the 
OA_CTXCTRL/FLEX_EU registers values as documented.
I can see that's it's a bit odd not to have the MI_LRI written before we 
do the first restore.

I'm 99% sure I've verified in practice that application started after 
i915/perf is opened have the right values programmed.
Not completely sure that the IGT tests cover that case though.
So maybe there is a problem with the first restore...

What's the value set into most register that aren't explicitly 
programmed in intel_lrc.c ?

-
Lionel

>
> Regards,
>
> Tvrtko
>

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