[Intel-gfx] [PATCH v3 2/3] drm/i915: Add GT support for multiple types of multicast steering

Matt Roper
2021-06-16T16:37:13Z

Although most of our multicast registers are replicated per-subslice, we
also have a small number of multicast registers that are replicated
per-l3 bank instead. For both types of multicast registers we need to
make sure we steer reads of these registers to a valid instance.
Ideally we'd like to find a specific instance ID that would steer reads
of either type of multicast register to a valid instance (i.e., not
fused off and not powered down), but sometimes the combination of
part-specific fusing and the additional restrictions imposed by Render
Power Gating make it impossible to find any overlap between the set of
valid subslices and valid l3 banks. This problem will become even more
noticeable on our upcoming platforms since they will be adding
additional types of multicast registers with new types of replication
and rules for finding valid instances for reads.

To handle this we'll continue to pick a suitable subslice instance at
driver startup and program this as the default (sliceid,subsliceid)
setting in the steering control register (0xFDC). In cases where we
need to read another type of multicast GT register, but the default
subslice steering would not correspond to a valid instance, we'll
explicitly re-steer the single read to a valid value, perform the read,
and then reset the steering to it's "subslice" default.

This patch adds the general functionality to prepare for this explicit
steering of other multicast register types. We'll plug L3 bank steering
into this in the next patch, and then add additional types of multicast
registers when the support for our next upcoming platform arrives.

v2:
- Use entry->end==0 as table terminator. (Rodrigo)
- Grab forcewake in wa_list_verify() now that we're using accessors
that assume forcewake is already held.

v3:
- Fix loop condition when iterating over steering range tables.
(Rodrigo)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
---
drivers/gpu/drm/i915/gt/intel_gt.c | 84 +++++++++++++++++++
drivers/gpu/drm/i915/gt/intel_gt.h | 8 ++
drivers/gpu/drm/i915/gt/intel_gt_types.h | 22 +++++
drivers/gpu/drm/i915/gt/intel_workarounds.c | 39 ++++++---
.../gpu/drm/i915/gt/selftest_workarounds.c | 2 +-
5 files changed, 142 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 2161bf01ef8b..80badc54b19d 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -697,6 +697,90 @@ void intel_gt_driver_late_release(struct intel_gt *gt)
intel_engines_free(gt);
}

+/**
+ * intel_gt_reg_needs_read_steering - determine whether a register read
+ * requires explicit steering
+ * @gt: GT structure
+ * @reg: the register to check steering requirements for
+ * @type: type of multicast steering to check
+ *
+ * Determines whether @reg needs explicit steering of a specific type for
+ * reads.
+ *
+ * Returns false if @reg does not belong to a register range of the given
+ * steering type, or if the default (subslice-based) steering IDs are suitable
+ * for @type steering too.
+ */
+static bool intel_gt_reg_needs_read_steering(struct intel_gt *gt,
+ i915_reg_t reg,
+ enum intel_steering_type type)
+{
+ const u32 offset = i915_mmio_reg_offset(reg);
+ const struct intel_mmio_range *entry;
+
+ if (likely(!intel_gt_needs_read_steering(gt, type)))
+ return false;
+
+ for (entry = gt->steering_table[type]; entry->end; entry++) {
+ if (offset >= entry->start && offset <= entry->end)
+ return true;
+ }
+
+ return false;
+}
+
+/**
+ * intel_gt_get_valid_steering - determines valid IDs for a class of MCR steering
+ * @gt: GT structure
+ * @type: multicast register type
+ * @sliceid: Slice ID returned
+ * @subsliceid: Subslice ID returned
+ *
+ * Determines sliceid and subsliceid values that will steer reads
+ * of a specific multicast register class to a valid value.
+ */
+static void intel_gt_get_valid_steering(struct intel_gt *gt,
+ enum intel_steering_type type,
+ u8 *sliceid, u8 *subsliceid)
+{
+ switch (type) {
+ default:
+ MISSING_CASE(type);
+ *sliceid = 0;
+ *subsliceid = 0;
+ }
+}
+
+/**
+ * intel_gt_read_register_fw - reads a GT register with support for multicast
+ * @gt: GT structure
+ * @reg: register to read
+ *
+ * This function will read a GT register. If the register is a multicast
+ * register, the read will be steered to a valid instance (i.e., one that
+ * isn't fused off or powered down by power gating).
+ *
+ * Returns the value from a valid instance of @reg.
+ */
+u32 intel_gt_read_register_fw(struct intel_gt *gt, i915_reg_t reg)
+{
+ int type;
+ u8 sliceid, subsliceid;
+
+ for (type = 0; type < NUM_STEERING_TYPES; type++) {
+ if (intel_gt_reg_needs_read_steering(gt, reg, type)) {
+ intel_gt_get_valid_steering(gt, type, &sliceid,
+ &subsliceid);
+ return intel_uncore_read_with_mcr_steering_fw(gt->uncore,
+ reg,
+ sliceid,
+ subsliceid);
+ }
+ }
+
+ return intel_uncore_read_fw(gt->uncore, reg);
+}
+
void intel_gt_info_print(const struct intel_gt_info *info,
struct drm_printer *p)
{
diff --git a/drivers/gpu/drm/i915/gt/intel_gt.h b/drivers/gpu/drm/i915/gt/intel_gt.h
index 7ec395cace69..e7aabe0cc5bf 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt.h
@@ -75,6 +75,14 @@ static inline bool intel_gt_is_wedged(const struct intel_gt *gt)
return unlikely(test_bit(I915_WEDGED, &gt->reset.flags));
}

+static inline bool intel_gt_needs_read_steering(struct intel_gt *gt,
+ enum intel_steering_type type)
+{
+ return gt->steering_table[type];
+}
+
+u32 intel_gt_read_register_fw(struct intel_gt *gt, i915_reg_t reg);
+
void intel_gt_info_print(const struct intel_gt_info *info,
struct drm_printer *p);

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
index fecfacf551d5..f2c274eee1e6 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
@@ -31,6 +31,26 @@ struct i915_ggtt;
struct intel_engine_cs;
struct intel_uncore;

+struct intel_mmio_range {
+ u32 start;
+ u32 end;
+};
+
+/*
+ * The hardware has multiple kinds of multicast register ranges that need
+ * special register steering (and future platforms are expected to add
+ * additional types).
+ *
+ * During driver startup, we initialize the steering control register to
+ * direct reads to a slice/subslice that are valid for the 'subslice' class
+ * of multicast registers. If another type of steering does not have any
+ * overlap in valid steering targets with 'subslice' style registers, we will
+ * need to explicitly re-steer reads of registers of the other type.
+ */
+enum intel_steering_type {
+ NUM_STEERING_TYPES
+};
+
enum intel_submission_method {
INTEL_SUBMISSION_RING,
INTEL_SUBMISSION_ELSP,
@@ -145,6 +165,8 @@ struct intel_gt {

struct i915_vma *scratch;

+ const struct intel_mmio_range *steering_table[NUM_STEERING_TYPES];
+
struct intel_gt_info {
intel_engine_mask_t engine_mask;
u8 num_engines;
diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
index 977a76e648e0..93c74d4cae02 100644
--- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
@@ -1248,8 +1248,9 @@ wa_verify(const struct i915_wa *wa, u32 cur, const char *name, const char *from)
}

static void
-wa_list_apply(struct intel_uncore *uncore, const struct i915_wa_list *wal)
+wa_list_apply(struct intel_gt *gt, const struct i915_wa_list *wal)
{
+ struct intel_uncore *uncore = gt->uncore;
enum forcewake_domains fw;
unsigned long flags;
struct i915_wa *wa;
@@ -1264,13 +1265,16 @@ wa_list_apply(struct intel_uncore *uncore, const struct i915_wa_list *wal)
intel_uncore_forcewake_get__locked(uncore, fw);

for (i = 0, wa = wal->list; i < wal->count; i++, wa++) {
- if (wa->clr)
- intel_uncore_rmw_fw(uncore, wa->reg, wa->clr, wa->set);
- else
- intel_uncore_write_fw(uncore, wa->reg, wa->set);
+ u32 val, old = 0;
+
+ /* open-coded rmw due to steering */
+ old = wa->clr ? intel_gt_read_register_fw(gt, wa->reg) : 0;
+ val = (old & ~wa->clr) | wa->set;
+ if (val != old || !wa->clr)
+ intel_uncore_write_fw(uncore, wa->reg, val);
+
if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
- wa_verify(wa,
- intel_uncore_read_fw(uncore, wa->reg),
+ wa_verify(wa, intel_gt_read_register_fw(gt, wa->reg),
wal->name, "application");
}

@@ -1280,28 +1284,39 @@ wa_list_apply(struct intel_uncore *uncore, const struct i915_wa_list *wal)

void intel_gt_apply_workarounds(struct intel_gt *gt)
{
- wa_list_apply(gt->uncore, &gt->i915->gt_wa_list);
+ wa_list_apply(gt, &gt->i915->gt_wa_list);
}

-static bool wa_list_verify(struct intel_uncore *uncore,
+static bool wa_list_verify(struct intel_gt *gt,
const struct i915_wa_list *wal,
const char *from)
{
+ struct intel_uncore *uncore = gt->uncore;
struct i915_wa *wa;
+ enum forcewake_domains fw;
+ unsigned long flags;
unsigned int i;
bool ok = true;

+ fw = wal_get_fw_for_rmw(uncore, wal);
+
+ spin_lock_irqsave(&uncore->lock, flags);
+ intel_uncore_forcewake_get__locked(uncore, fw);
+
for (i = 0, wa = wal->list; i < wal->count; i++, wa++)
ok &= wa_verify(wa,
- intel_uncore_read(uncore, wa->reg),
+ intel_gt_read_register_fw(gt, wa->reg),
wal->name, from);

+ intel_uncore_forcewake_put__locked(uncore, fw);
+ spin_unlock_irqrestore(&uncore->lock, flags);
+
return ok;
}

bool intel_gt_verify_workarounds(struct intel_gt *gt, const char *from)
{
- return wa_list_verify(gt->uncore, &gt->i915->gt_wa_list, from);
+ return wa_list_verify(gt, &gt->i915->gt_wa_list, from);
}

__maybe_unused
@@ -2084,7 +2099,7 @@ void intel_engine_init_workarounds(struct intel_engine_cs *engine)

void intel_engine_apply_workarounds(struct intel_engine_cs *engine)
{
- wa_list_apply(engine->uncore, &engine->wa_list);
+ wa_list_apply(engine->gt, &engine->wa_list);
}

struct mcr_range {
diff --git a/drivers/gpu/drm/i915/gt/selftest_workarounds.c b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
index c30754daf4b1..7ebc4edb8ecf 100644
--- a/drivers/gpu/drm/i915/gt/selftest_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
@@ -1147,7 +1147,7 @@ verify_wa_lists(struct intel_gt *gt, struct wa_lists *lists,
enum intel_engine_id id;
bool ok = true;

- ok &= wa_list_verify(gt->uncore, &lists->gt_wa_list, str);
+ ok &= wa_list_verify(gt, &lists->gt_wa_list, str);

for_each_engine(engine, gt, id) {
struct intel_context *ce;
--
2.25.4