Re: [Intel-gfx] [PATCH] drm/i915/uncore: Warn on previous unclaimed accesses

Lucas De Marchi
2022-04-08T15:00:11Z

On Fri, Apr 08, 2022 at 01:44:44PM +0100, Tvrtko Ursulin wrote:
>
>On 05/04/2022 01:11, Lucas De Marchi wrote:
>>Since gen6 we use FPGA_DBG register to detect unclaimed MMIO registers.
>>This register is in the display engine IP and can only ever detect
>>unclaimed accesses to registers in this area. However sometimes there
>>are reports of this triggering for registers in other areas, which
>>should not be possible.
>>
>>Right now we always warn after the read/write of registers going through
>>unclaimed_reg_debug(). However places using __raw_uncore_* may be
>>triggering the unclaimed access and those being later accounted to a
>>different register. Let's warn both before and after the read/write
>>with a slightly different message, so it's clear if the register
>>reported in the warning is actually the culprit.
>>
>>Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
>
>I see this triggering a lot on drm-tip today (TGL), is that expected?
>
>[ 3.994907] i915 0000:00:02.0: [drm:intel_uncore_init_mmio [i915]] unclaimed mmio detected on uncore init, clearing
>[ 4.392525] i915 0000:00:02.0: Unclaimed access detected before read from register 0x44408
>[ 5.669929] i915 0000:00:02.0: Unclaimed access detected before write to register 0x50380
>[ 6.652808] i915 0000:00:02.0: Unclaimed access detected before write to register 0x50380
>[ 13.015978] i915 0000:00:02.0: Unclaimed access detected before write to register 0x50380
>[ 16.876802] i915 0000:00:02.0: Unclaimed access detected before write to register 0x44404
>[ 45.174395] i915 0000:00:02.0: Unclaimed access detected before write to register 0x44404
>
>It continues at runtime as well:
>
>[10265.010902] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10329.093078] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10354.060331] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10385.486480] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10408.910533] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10433.398443] i915 0000:00:02.0: Unclaimed access detected before write to register 0x1900ec
>[10444.110593] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10468.302627] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10493.398727] i915 0000:00:02.0: Unclaimed access detected before write to register 0x1900ec
>[10515.366845] i915 0000:00:02.0: Unclaimed access detected before read from register 0x44408
>[10518.674046] i915 0000:00:02.0: Unclaimed access detected before read from register 0xc7204
>[10529.934735] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10553.398808] i915 0000:00:02.0: Unclaimed access detected before write to register 0x1900ec
>[10599.684455] i915 0000:00:02.0: Unclaimed access detected before read from register 0xc4008
>[10602.898167] i915 0000:00:02.0: Unclaimed access detected before read from register 0xc7204
>[10613.398909] i915 0000:00:02.0: Unclaimed access detected before write to register 0x1900ec
>[10686.006783] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10711.906813] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10745.860538] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10771.812277] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10805.903058] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10831.927073] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10853.398958] i915 0000:00:02.0: Unclaimed access detected before write to register 0x1900ec
>[10866.007084] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10879.378435] i915 0000:00:02.0: Unclaimed access detected before read from register 0xc7204
>[10891.727120] i915 0000:00:02.0: Unclaimed access detected before write to register 0x190030
>[10913.395161] i915 0000:00:02.0: Unclaimed access detected before write to register 0x1900ec
>[10939.026480] i915 0000:00:02.0: Unclaimed access detected before read from register 0xc7204
>[10964.626494] i915 0000:00:02.0: Unclaimed access detected before read from register 0xc7204
>
>It don't think this machine had a problem with this before, or perhaps it was going undetected?

it was going undetected. However I have a patch to downgrade the first
message to debug, because we are clear not ready to enable the stricter
check. I will send it in a bit.

Lucas De Marchi

>
>Regards,
>
>Tvrtko
>
>>---
>> drivers/gpu/drm/i915/intel_uncore.c | 29 +++++++++++++++++++++--------
>> 1 file changed, 21 insertions(+), 8 deletions(-)
>>
>>diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
>>index 8b9caaaacc21..df59ec88459e 100644
>>--- a/drivers/gpu/drm/i915/intel_uncore.c
>>+++ b/drivers/gpu/drm/i915/intel_uncore.c
>>@@ -1502,11 +1502,10 @@ ilk_dummy_write(struct intel_uncore *uncore)
>> static void
>> __unclaimed_reg_debug(struct intel_uncore *uncore,
>> const i915_reg_t reg,
>>- const bool read,
>>- const bool before)
>>+ const bool read)
>> {
>> if (drm_WARN(&uncore->i915->drm,
>>- check_for_unclaimed_mmio(uncore) && !before,
>>+ check_for_unclaimed_mmio(uncore),
>> "Unclaimed %s register 0x%x\n",
>> read ? "read from" : "write to",
>> i915_mmio_reg_offset(reg)))
>>@@ -1514,6 +1513,20 @@ __unclaimed_reg_debug(struct intel_uncore *uncore,
>> uncore->i915->params.mmio_debug--;
>> }
>>+static void
>>+__unclaimed_previous_reg_debug(struct intel_uncore *uncore,
>>+ const i915_reg_t reg,
>>+ const bool read)
>>+{
>>+ if (drm_WARN(&uncore->i915->drm,
>>+ check_for_unclaimed_mmio(uncore),
>>+ "Unclaimed access detected before %s register 0x%x\n",
>>+ read ? "read from" : "write to",
>>+ i915_mmio_reg_offset(reg)))
>>+ /* Only report the first N failures */
>>+ uncore->i915->params.mmio_debug--;
>>+}
>>+
>> static inline void
>> unclaimed_reg_debug(struct intel_uncore *uncore,
>> const i915_reg_t reg,
>>@@ -1526,13 +1539,13 @@ unclaimed_reg_debug(struct intel_uncore *uncore,
>> /* interrupts are disabled and re-enabled around uncore->lock usage */
>> lockdep_assert_held(&uncore->lock);
>>- if (before)
>>+ if (before) {
>> spin_lock(&uncore->debug->lock);
>>-
>>- __unclaimed_reg_debug(uncore, reg, read, before);
>>-
>>- if (!before)
>>+ __unclaimed_previous_reg_debug(uncore, reg, read);
>>+ } else {
>>+ __unclaimed_reg_debug(uncore, reg, read);
>> spin_unlock(&uncore->debug->lock);
>>+ }
>> }
>> #define __vgpu_read(x) \