On 04/03/2022 23:46, Matt Roper wrote:
From: Akeem G Abodunrin <akeem.g.abodunrin@xxxxxxxxx>
Since DG2 and beyond only support global preemption enable/disable (see
Wa_14015141709), userspace no longer has a way to control preemption on
a per-context basis. Preemption is globally enabled by default, but the
UMD teams have requested that we provide a debugfs interface that can be
used to query and adjust the system-wide preemption setting for
development and bug reporting purposes.
I guess most distros enable debugfs, anyone knows for sure? Otherwise
the bug reporting use case could be questionable.
And UMD acks would be desirable here I'd say.
v2 (MattR):
- Split debugfs out into a separate patch. (Jani)
- Add the hardware update/query as facilities in intel_gt.c and just
call them from the debugfs code. (Jani)
- Add register to GuC's save/restore list so that the value will
persist across resets. (Tvrtko)
- Place under per-GT debugfs rather than i915 debugfs. (MattR)
- Only register debugfs entries on platforms subject to Wa_14015141709,
and only on platforms that have an RCS engine. (MattR/Tvrtko)
Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
Cc: Prathap Kumar Valsan <prathap.kumar.valsan@xxxxxxxxx>
Cc: John Harrison <john.c.harrison@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@xxxxxxxxx>
Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_gt.c | 50 ++++++++++++++++++++++
drivers/gpu/drm/i915/gt/intel_gt.h | 3 ++
drivers/gpu/drm/i915/gt/intel_gt_debugfs.c | 31 ++++++++++++++
drivers/gpu/drm/i915/gt/intel_gt_regs.h | 3 ++
drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c | 7 +++
5 files changed, 94 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 8a2483ccbfb9..90bdebd8d267 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -1045,3 +1045,53 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
intel_uncore_forcewake_put_delayed(uncore, FORCEWAKE_ALL);
mutex_unlock(>->tlb_invalidate_lock);
}
+
+/**
+ * intel_gt_get_global_preemption - return whether the global preemption
+ * setting is enabled in hardware
+ * @gt: GT structure
+ *
+ * Returns the hardware's global 'preemption enabled' setting. Only relevant
+ * on newer platforms that lack per-context preemption control (and only on
+ * GTs that have a render engine).
+ *
+ * Returns 1 if preemption is enabled, 0 if disabled.
+ */
+u64 intel_gt_get_global_preemption(struct intel_gt *gt)
+{
+ intel_wakeref_t wakeref;
+ u32 val;
+
+ drm_WARN_ON(>->i915->drm, GRAPHICS_VER_FULL(gt->i915) < IP_VER(12, 55));
+ drm_WARN_ON(>->i915->drm, RCS_MASK(gt) == 0);
+
+ with_intel_runtime_pm(>->i915->runtime_pm, wakeref)
+ val = intel_uncore_read(gt->uncore, GEN12_VFG_PREEMPTION_CHICKEN);
+
+ return !(val & GEN12_VFG_PREEMPT_CHICKEN_DISABLE);
+}
+
+/**
+ * intel_gt_set_global_preemption - adjust global preemption enabled setting
+ * @gt: GT structure
+ * @val: desired preemption setting
+ *
+ * Enables global preemption if @val is non-zero, otherwise disables it. Only
+ * relevant on newer platforms that lack per-context preemption control (and
+ * only on GTs that have a render engine).
+ *
+ * Returns 1 if preemption is enabled, 0 if disabled.
+ */
+void intel_gt_set_global_preemption(struct intel_gt *gt, u64 val)
+{
+ intel_wakeref_t wakeref;
+ u32 tmp = val ?
+ _MASKED_BIT_DISABLE(GEN12_VFG_PREEMPT_CHICKEN_DISABLE) :
+ _MASKED_BIT_ENABLE(GEN12_VFG_PREEMPT_CHICKEN_DISABLE);
+
+ drm_WARN_ON(>->i915->drm, GRAPHICS_VER_FULL(gt->i915) < IP_VER(12, 55));
+ drm_WARN_ON(>->i915->drm, RCS_MASK(gt) == 0);
Bike shedding territory, but as long as these checks are present in
release builds, it would be possible to return an error and propagate to
debugfs caller/return. Not saying to do it just thinking out loud.
+
+ with_intel_runtime_pm(>->i915->runtime_pm, wakeref)
+ intel_uncore_write(gt->uncore, GEN12_VFG_PREEMPTION_CHICKEN, tmp);
+}
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.h b/drivers/gpu/drm/i915/gt/intel_gt.h
index 0f571c8ee22b..63a599a1bf6d 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt.h
@@ -94,4 +94,7 @@ void intel_gt_watchdog_work(struct work_struct *work);
void intel_gt_invalidate_tlbs(struct intel_gt *gt);
+u64 intel_gt_get_global_preemption(struct intel_gt *gt);
+void intel_gt_set_global_preemption(struct intel_gt *gt, u64 val);
Bool based would be nicer unless there is some reason for 64-bits in the
future.
Regards,
Tvrtko
+
#endif /* __INTEL_GT_H__ */
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_debugfs.c b/drivers/gpu/drm/i915/gt/intel_gt_debugfs.c
index f103664b71d4..d851e3f80877 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_debugfs.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_debugfs.c
@@ -6,6 +6,7 @@
#include <linux/debugfs.h>
#include "i915_drv.h"
+#include "intel_gt.h"
#include "intel_gt_debugfs.h"
#include "intel_gt_engines_debugfs.h"
#include "intel_gt_pm_debugfs.h"
@@ -57,13 +58,43 @@ static int __intel_gt_debugfs_reset_store(void *data, u64 val)
DEFINE_SIMPLE_ATTRIBUTE(reset_fops, __intel_gt_debugfs_reset_show,
__intel_gt_debugfs_reset_store, "%llu\n");
+static int i915_global_preemption_enabled_get(void *data, u64 *val)
+{
+ *val = intel_gt_get_global_preemption((struct intel_gt *)data);
+
+ return 0;
+}
+
+static int i915_global_preemption_enabled_set(void *data, u64 val)
+{
+ intel_gt_set_global_preemption((struct intel_gt *)data, val);
+
+ return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(i915_global_preemption_enabled_fops,
+ i915_global_preemption_enabled_get,
+ i915_global_preemption_enabled_set,
+ "%llu\n");
+
static void gt_debugfs_register(struct intel_gt *gt, struct dentry *root)
{
static const struct intel_gt_debugfs_file files[] = {
{ "reset", &reset_fops, NULL },
};
+ static const struct intel_gt_debugfs_file preempt_files[] = {
+ { "preemption_enabled", &i915_global_preemption_enabled_fops }
+ };
intel_gt_debugfs_register_files(root, files, ARRAY_SIZE(files), gt);
+
+ /*
+ * Global preemption control only applies to DG2 and beyond
+ * (Wa_14015141709) and only to GTs with an RCS.
+ */
+ if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 55) && RCS_MASK(gt))
+ intel_gt_debugfs_register_files(root, preempt_files,
+ ARRAY_SIZE(preempt_files), gt);
}
void intel_gt_debugfs_register(struct intel_gt *gt)
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
index 19cd34f24263..21ede1887b9f 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
@@ -468,6 +468,9 @@
#define VF_PREEMPTION _MMIO(0x83a4)
#define PREEMPTION_VERTEX_COUNT REG_GENMASK(15, 0)
+#define GEN12_VFG_PREEMPTION_CHICKEN _MMIO(0x83b4)
+#define GEN12_VFG_PREEMPT_CHICKEN_DISABLE REG_BIT(8)
+
#define GEN8_RC6_CTX_INFO _MMIO(0x8504)
#define GEN12_SQCM _MMIO(0x8724)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c
index acc4a3766dc1..7e008382ab03 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c
@@ -352,6 +352,13 @@ static int guc_mmio_regset_init(struct temp_regset *regset,
for (i = 0; i < GEN9_LNCFCMOCS_REG_COUNT; i++)
ret |= GUC_MMIO_REG_ADD(regset, GEN9_LNCFCMOCS(i), false);
+ /*
+ * VFG_PREEMPTION_CHICKEN can be controlled via debugfs; ensure
+ * the setting sticks across resets
+ */
+ if (engine->flags & I915_ENGINE_FIRST_RENDER_COMPUTE)
+ ret |= GUC_MMIO_REG_ADD(regset, GEN12_VFG_PREEMPTION_CHICKEN, true);
+
return ret ? -1 : 0;
}
