linux-kernel - [RFC PATCH] drm/panfrost: Handle IDVS_GROUP

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Date:   Sun,  9 Jan 2022 12:12:54 -0500
From:   Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Rob Herring <robh@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Steven Price <steven.price@....com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org
Subject: [RFC PATCH] drm/panfrost: Handle IDVS_GROUP_SIZE feature

The IDVS group size feature was missing. It is used on some Bifrost and
Valhall GPUs, and is the last kernel-relevant Bifrost feature we're
missing.

This feature adds an extra IDVS group size field to the JM_CONFIG
register. In kbase, the value is configurable via the device tree; kbase
uses 0xF as a default if no value is specified. Until we find a device
demanding otherwise, let's always set the 0xF default on devices which
support this feature mimicking kbase's behaviour.

As JM_CONFIG is an undocumented register, it's not clear to me what
happens if we fail to include this handling. Index-driven vertex shading
already works on Bifrost boards with this feature without this handling.
Perhaps this has performance implications? Patch untested for the
moment, wanted to give Steven a chance to comment.

Applies on top of my feature clean up series which should go in first.
(That's pure cleaunp, this is a behaviour change RFC needing
discussion.)

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>
---
 drivers/gpu/drm/panfrost/panfrost_features.h | 3 +++
 drivers/gpu/drm/panfrost/panfrost_gpu.c      | 3 +++
 drivers/gpu/drm/panfrost/panfrost_regs.h     | 1 +
 3 files changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/panfrost/panfrost_features.h b/drivers/gpu/drm/panfrost/panfrost_features.h
index 34f2bae1ec8c..36fadcf9634e 100644
--- a/drivers/gpu/drm/panfrost/panfrost_features.h
+++ b/drivers/gpu/drm/panfrost/panfrost_features.h
@@ -20,6 +20,7 @@ enum panfrost_hw_feature {
 	HW_FEATURE_AARCH64_MMU,
 	HW_FEATURE_TLS_HASHING,
 	HW_FEATURE_THREAD_GROUP_SPLIT,
+	HW_FEATURE_IDVS_GROUP_SIZE,
 	HW_FEATURE_3BIT_EXT_RW_L2_MMU_CONFIG,
 };
 
@@ -74,6 +75,7 @@ enum panfrost_hw_feature {
 	BIT_ULL(HW_FEATURE_FLUSH_REDUCTION) | \
 	BIT_ULL(HW_FEATURE_PROTECTED_MODE) | \
 	BIT_ULL(HW_FEATURE_PROTECTED_DEBUG_MODE) | \
+	BIT_ULL(HW_FEATURE_IDVS_GROUP_SIZE) | \
 	BIT_ULL(HW_FEATURE_COHERENCY_REG))
 
 #define hw_features_g76 (\
@@ -87,6 +89,7 @@ enum panfrost_hw_feature {
 	BIT_ULL(HW_FEATURE_COHERENCY_REG) | \
 	BIT_ULL(HW_FEATURE_AARCH64_MMU) | \
 	BIT_ULL(HW_FEATURE_TLS_HASHING) | \
+	BIT_ULL(HW_FEATURE_IDVS_GROUP_SIZE) | \
 	BIT_ULL(HW_FEATURE_3BIT_EXT_RW_L2_MMU_CONFIG))
 
 #define hw_features_g31 (\
diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.c b/drivers/gpu/drm/panfrost/panfrost_gpu.c
index bbe628b306ee..50c8922694d7 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gpu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gpu.c
@@ -145,6 +145,9 @@ static void panfrost_gpu_init_quirks(struct panfrost_device *pfdev)
 		quirks |= (COHERENCY_ACE_LITE | COHERENCY_ACE) <<
 			   JM_FORCE_COHERENCY_FEATURES_SHIFT;
 
+	if (panfrost_has_hw_feature(pfdev, HW_FEATURE_IDVS_GROUP_SIZE))
+		quirks |= JM_DEFAULT_IDVS_GROUP_SIZE << JM_IDVS_GROUP_SIZE_SHIFT;
+
 	if (quirks)
 		gpu_write(pfdev, GPU_JM_CONFIG, quirks);
 
diff --git a/drivers/gpu/drm/panfrost/panfrost_regs.h b/drivers/gpu/drm/panfrost/panfrost_regs.h
index 6c5a11ef1ee8..16e776cc82ea 100644
--- a/drivers/gpu/drm/panfrost/panfrost_regs.h
+++ b/drivers/gpu/drm/panfrost/panfrost_regs.h
@@ -208,6 +208,7 @@
 #define JM_MAX_JOB_THROTTLE_LIMIT	0x3F
 #define JM_FORCE_COHERENCY_FEATURES_SHIFT 2
 #define JM_IDVS_GROUP_SIZE_SHIFT	16
+#define JM_DEFAULT_IDVS_GROUP_SIZE	0xF
 #define JM_MAX_IDVS_GROUP_SIZE		0x3F
 
 
-- 
2.34.1