Re: [PATCH v2 03/12] drm/i915/skl: Use revid->stepping tables

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On Fri, Jul 09, 2021 at 08:37:15PM -0700, Matt Roper wrote:
Switch SKL to use a revid->stepping table as we're trying to do on all
platforms going forward.  Also drop the preproduction revisions and add
the newer steppings we hadn't already handled.

Note that SKL has a case where a newer revision ID corresponds to an
older GT/disp stepping (0x9 -> STEP_J0, 0xA -> STEP_I1).  Also, the lack
of a revision ID 0x8 in the table is intentional and not an oversight.
We'll re-write the KBL-specific comment to make it clear that these kind
of quirks are expected.

v2:
- Since GT and display steppings are always identical on SKL use a
  macro to set both values at once in a more readable manner.  (Anusha)
- Drop preproduction steppings.

Bspec: 13626
Cc: Anusha Srivatsa <anusha.srivatsa@xxxxxxxxx>
Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_workarounds.c |  2 +-
drivers/gpu/drm/i915/i915_drv.h             | 11 +-------
drivers/gpu/drm/i915/intel_step.c           | 30 +++++++++++++++++----
drivers/gpu/drm/i915/intel_step.h           |  4 +++
4 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
index d9a5a445ceec..6dfd564e078f 100644
--- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
@@ -883,7 +883,7 @@ skl_gt_workarounds_init(struct drm_i915_private *i915, struct i915_wa_list *wal)
		    GEN8_EU_GAUNIT_CLOCK_GATE_DISABLE);

	/* WaInPlaceDecompressionHang:skl */
-	if (IS_SKL_REVID(i915, SKL_REVID_H0, REVID_FOREVER))
+	if (IS_SKL_GT_STEP(i915, STEP_H0, STEP_FOREVER))
		wa_write_or(wal,
			    GEN9_GAMT_ECO_REG_RW_IA,
			    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index c4747f4407ef..f30499ed6787 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1515,16 +1515,7 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
#define IS_TGL_Y(dev_priv) \
	IS_SUBPLATFORM(dev_priv, INTEL_TIGERLAKE, INTEL_SUBPLATFORM_ULX)

-#define SKL_REVID_A0		0x0
-#define SKL_REVID_B0		0x1
-#define SKL_REVID_C0		0x2
-#define SKL_REVID_D0		0x3
-#define SKL_REVID_E0		0x4
-#define SKL_REVID_F0		0x5
-#define SKL_REVID_G0		0x6
-#define SKL_REVID_H0		0x7
-
-#define IS_SKL_REVID(p, since, until) (IS_SKYLAKE(p) && IS_REVID(p, since, until))
+#define IS_SKL_GT_STEP(p, since, until) (IS_SKYLAKE(p) && IS_GT_STEP(p, since, until))

#define BXT_REVID_A0		0x0
#define BXT_REVID_A1		0x1
diff --git a/drivers/gpu/drm/i915/intel_step.c b/drivers/gpu/drm/i915/intel_step.c
index 93ccd42f2514..69c928b046e8 100644
--- a/drivers/gpu/drm/i915/intel_step.c
+++ b/drivers/gpu/drm/i915/intel_step.c
@@ -7,14 +7,31 @@
#include "intel_step.h"

/*
- * KBL revision ID ordering is bizarre; higher revision ID's map to lower
- * steppings in some cases.  So rather than test against the revision ID
- * directly, let's map that into our own range of increasing ID's that we
- * can test against in a regular manner.
+ * Some platforms have unusual ways of mapping PCI revision ID to GT/display
+ * steppings.  E.g., in some cases a higher PCI revision may translate to a
+ * lower stepping of the GT and/or display IP.  This file provides lookup
+ * tables to map the PCI revision into a standard set of stepping values that
+ * can be compared numerically.
+ *
+ * Also note that some revisions/steppings may have been set aside as
+ * placeholders but never materialized in real hardware; in those cases there
+ * may be jumps in the revision IDs or stepping values in the tables below.
 */

+/*
+ * Some platforms always have the same stepping value for GT and display;
+ * use a macro to define these to make it easier to identify the platforms
+ * where the two steppings can deviate.
+ */
+#define COMMON_STEPPING(x)  .gt_step = STEP_##x, .display_step = STEP_##x

nitpick:

"stepping" is the proper word, but we settled on "step"
everyhere: functions, macros, tables, filename etc. Can we
continue doing that?  For the comments I think it's ok to
continue using the proper word, but for real code I think it
would be better to keep it consistent

thanks
Lucas De Marchi
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