On 15/05/2023 23:07, Dixit, Ashutosh wrote:
On Mon, 15 May 2023 03:10:56 -0700, Tvrtko Ursulin wrote:
Hi Tvrtko,
On 12/05/2023 21:57, Umesh Nerlige Ramappa wrote:
On Fri, May 12, 2023 at 11:56:18AM +0100, Tvrtko Ursulin wrote:
On 12/05/2023 02:08, Dixit, Ashutosh wrote:
On Fri, 05 May 2023 17:58:15 -0700, Umesh Nerlige Ramappa wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Reserve some bits in the counter config namespace which will carry the
tile id and prepare the code to handle this.
No per tile counters have been added yet.
v2:
- Fix checkpatch issues
- Use 4 bits for gt id in non-engine counters. Drop FIXME.
- Set MAX GTs to 4. Drop FIXME.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
8<
+static u64 frequency_enabled_mask(void)
+{
+ unsigned int i;
+ u64 mask = 0;
+
+ for (i = 0; i < I915_PMU_MAX_GTS; i++)
+ mask |= config_mask(__I915_PMU_ACTUAL_FREQUENCY(i)) |
+ config_mask(__I915_PMU_REQUESTED_FREQUENCY(i));
+
+ return mask;
+}
+
static bool pmu_needs_timer(struct i915_pmu *pmu, bool gpu_active)
{
struct drm_i915_private *i915 = container_of(pmu, typeof(*i915),
pmu);
@@ -120,9 +147,7 @@ static bool pmu_needs_timer(struct i915_pmu *pmu,
bool gpu_active)
* Mask out all the ones which do not need the timer, or in
* other words keep all the ones that could need the timer.
*/
- enable &= config_mask(I915_PMU_ACTUAL_FREQUENCY) |
- config_mask(I915_PMU_REQUESTED_FREQUENCY) |
- ENGINE_SAMPLE_MASK;
+ enable &= frequency_enabled_mask() | ENGINE_SAMPLE_MASK;
u32 enable & u64 frequency_enabled_mask
ugly but ok I guess? Or change enable to u64?
making pmu->enable u64 as well as other places where it is assigned to
local variables.
Hmm.. yes very ugly. Could have been an accident which happened to work
because there is a single timer (not per tile).
Happened to work because the frequency mask does not spill over to the
upper 32 bits (even for multi tile).
--------------------- START_SECTION ----------------
Similar issue in frequency_sampling_enabled too. Gt_id argument to it
seems pointless.
Not sure why it's pointless. We need the gt_id to determine the right
mask for that specific gt. If it's not enabled, then we just return
without pm_get and async put (like you mention later).
And this piece of code is called within for_each_gt.
I think I got a little confused cross referencing the code and patches last
week and did not mentally see all the changes.
Because the hunk in other_bit() is correctly adding support for per gt bits.
The layout of pmu->enable ends up like this:
bits 0 - 2: engine events
bits 3 - 5: gt0 other events
bits 6 - 8: gt1 other events
bits 9 - 11: gt2 other events
bits 12 - 14: gt3 other events
Correct.
So I now think whole frequency_enabled_mask() is just pointless and
should be removed. And then pmu_needs_time code can stay as is. Possibly
add a config_mask_32 helper which ensures no bits in upper 32 bits are
returned.
That is if we are happy for the frequency_sampling_enabled returning
true for all gts, regardless of which ones actually have frequency
sampling enabled.
Or if we want to implement it as I probably have intended, we will need
to add some gt bits into pmu->enable. Maybe reserve top four same as
with config counters.
Nope. What you have here works just fine. pmu->enable should not include
any gt id info. gt_id[63:60] is only a concept for pmu config sent by
user. config_mask and pmu->enable are i915 internal bookkeeping (bit
masks) just to track what events need to be sampled. The 'other' bit
masks are a function of gt_id because we use gt_id to calculate a
contiguous numerical value for these 'other' events. That's all. Once the
numerical value is calculated, there is no need for gt_id because
config_mask is BIT_ULL(numerical_value). Since the numerical values never
exceeded 31 (even for multi-gts), everything worked even with 32 bit
pmu->enable.
Yep.
So question then is why make pmu->enable u64?
The only reason was simplicity, since a lot of the existing code already
assumes u64.
E.g. if we keep pmu->enable u32, we should have to do the following:
* Change config_mask() return type to u32 (in frequency_sampling_enabled(),
we have 'pmu->enable & config_mask()')
* Change frequency_enabled_mask() return type to u32 (again uses
config_mask() so if we change config_mask() to u32 we change return type
here too)
* In i915_pmu_enable(), change 'pmu->enable |= BIT_ULL(bit)' to
'pmu->enable |= BIT(bit)'
So yes, if we think we should be using pmu->enable u32, let's change this
to be consistent everywhere.
Instead frequency_enabled_mask() should be made u32 since the bitwise or
composition of config_masks() is guaranteed to fit.
At most it can have an internal u64 for the mask, assert upper_32_bits are
zero and return lower_32_bits.
Did I get it right this time round? :)
Yes, though we'd have to make the config_mask() type change above to make
frequency_enabled_mask() u32. Or we can just keep everything u64. Let's
decide one way or the other and close this. It seems Tvrtko is leaning
towards making pmu->enable and frequency_enabled_mask() u32?
I think so. Since it seems u64 for config_mask() was a mistake from the
start lets fix it up. I can send a patch to do that if easier?
Regards,
Tvrtko
