[PATCH v5 6/6] drm/xe: disable wa_15015404425 for PTL B0

[Matt Atwood]

Wa_15015404425 only needs to be applied on PTL platforms with an A step
compute die. There is no way to map PCI revid to the compute die
stepping. The easiest way to figure out compute die stepping our end is
to map the media IP's stepping to the compute die. For PTL, compute die
has an A stepping if and only if the media IP's stepping is also A-step
(This relationship is determined on a per platform basis and just
happens to be this way on PTL).

In addition this workaround is a chicken-and-egg problem. Wa_15015404425
requires that all register reads be preceded by four dummy MMIO writes
(including during early driver  init and even pre-OS firmware). The
driver needs to perform some MMIO reads during init which include the
GMD_ID register that contains the Media IPs stepping. To handle this in
the safest manner assume the workaround applies to all of PTL during
driver probe and deactivate the workaround after.

The overall solution becomes a set of two workarounds:

* 15015404425 - a Device OOB workaround that's always active for PTL
* 15015404425_disable - a GT OOB workaround that applies to PTL
  platfroms with a B0 or later stepping

The first of these workarounds issues dummy MMIO writes we do when
reading registers. The second guards logic that disables the first once
we have the necessary information later in the probe process.

v2: rename SoC to device, avoid null pointer dereference, update commit
message.
v3: rebase
v5: move disable check into xe_device_probe to avoid linking in xe_wa
into xe_pci, reword commit message

Signed-off-by: Matt Atwood <matthew.s.atwood at intel.com>
---
 drivers/gpu/drm/xe/xe_device.c     | 5 +++++
 drivers/gpu/drm/xe/xe_wa.h         | 5 +++++
 drivers/gpu/drm/xe/xe_wa_oob.rules | 2 ++
 3 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 53df142c1031..5a771b0f8f19 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -68,6 +68,7 @@
 #include "xe_wa.h"
 
 #include <generated/xe_wa_oob.h>
+#include <generated/xe_device_wa_oob.h>
 
 static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 {
@@ -863,6 +864,10 @@ int xe_device_probe(struct xe_device *xe)
 			return err;
 	}
 
+	if (xe->tiles->media_gt &&
+	    XE_WA(xe->tiles->media_gt, 15015404425_disable))
+		XE_DEVICE_WA_DISABLE(xe, 15015404425);
+
 	xe_nvm_init(xe);
 
 	err = xe_heci_gsc_init(xe);
diff --git a/drivers/gpu/drm/xe/xe_wa.h b/drivers/gpu/drm/xe/xe_wa.h
index 3793fcae38a0..907eea020b9d 100644
--- a/drivers/gpu/drm/xe/xe_wa.h
+++ b/drivers/gpu/drm/xe/xe_wa.h
@@ -45,4 +45,9 @@ void xe_wa_dump(struct xe_gt *gt, struct drm_printer *p);
 	test_bit(XE_DEVICE_WA_OOB_ ## id__, (xe__)->wa_active.oob);		\
 })
 
+#define XE_DEVICE_WA_DISABLE(xe__, id__) ({				\
+	xe_assert(xe__, (xe__)->wa_active.oob_initialized);			\
+	clear_bit(XE_DEVICE_WA_OOB_ ## id__, (xe__)->wa_active.oob);		\
+})
+
 #endif
diff --git a/drivers/gpu/drm/xe/xe_wa_oob.rules b/drivers/gpu/drm/xe/xe_wa_oob.rules
index 96cc33da0fb5..255e67113406 100644
--- a/drivers/gpu/drm/xe/xe_wa_oob.rules
+++ b/drivers/gpu/drm/xe/xe_wa_oob.rules
@@ -70,3 +70,5 @@ no_media_l3	MEDIA_VERSION(3000)
 # SoC workaround - currently applies to all platforms with the following
 # primary GT GMDID
 14022085890	GRAPHICS_VERSION(2001)
+
+15015404425_disable	PLATFORM(PANTHERLAKE), MEDIA_STEP(B0, FOREVER)
-- 
2.49.0