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

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On 15/08/18 11:56, Chris Wilson wrote:
Quoting Lionel Landwerlin (2018-08-15 11:50:55)
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@xxxxxxxxx>

Abstract the context image access a bit.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
     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 ?
That would be whatever was previously there

In practice, since we now initialise all real contexts from the default
state, the LRI will be there. execlists_init_reg_state() is wonderfully,
perhaps dangerously, misleading atm.
-Chris

Then I guess it's all fine :)
Thanks,

-
Lionel
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