[PATCH 0/2] drm/panthor: add custom ASN hash support

[PATCH 0/2] drm/panthor: add custom ASN hash support

[Chia-I Wu]

Some socs such as mt8196 require custom ASN hash.

Chia-I Wu (2):
  dt-bindings: gpu: mali-valhall-csf: add asn-hash
  drm/panthor: add asn-hash support

 .../bindings/gpu/arm,mali-valhall-csf.yaml    |  8 ++++++
 drivers/gpu/drm/panthor/panthor_device.c      | 28 +++++++++++++++++++
 drivers/gpu/drm/panthor/panthor_device.h      |  6 ++++
 drivers/gpu/drm/panthor/panthor_gpu.c         | 17 +++++++++++
 drivers/gpu/drm/panthor/panthor_regs.h        |  4 +++
 5 files changed, 63 insertions(+)

-- 
2.51.0.318.gd7df087d1a-goog

[PATCH 1/2] dt-bindings: gpu: mali-valhall-csf: add asn-hash

[Chia-I Wu]

The values are written to ASN_HASH[0..2] registers. The property is
called "l2-hash-values" in the downstream driver.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
---
 .../devicetree/bindings/gpu/arm,mali-valhall-csf.yaml     | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
index a5b4e00217587..258bcba66d1d1 100644
--- a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
+++ b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
@@ -85,6 +85,14 @@ properties:
 
   dma-coherent: true
 
+  asn-hash:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description:
+      The values are written to ASN_HASH[0..2] registers. They affect how
+      physical addresses are mapped to L2 cache slices.
+    minItems: 3
+    maxItems: 3
+
 required:
   - compatible
   - reg
-- 
2.51.0.318.gd7df087d1a-goog

[PATCH 2/2] drm/panthor: add asn-hash support

[Chia-I Wu]

Parse asn-hash and enable custom ASN hash when the property exists.
This is required on some socs such as mt8196.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
---
 drivers/gpu/drm/panthor/panthor_device.c | 28 ++++++++++++++++++++++++
 drivers/gpu/drm/panthor/panthor_device.h |  6 +++++
 drivers/gpu/drm/panthor/panthor_gpu.c    | 17 ++++++++++++++
 drivers/gpu/drm/panthor/panthor_regs.h   |  4 ++++
 4 files changed, 55 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index 81df49880bd87..19423c495d8d7 100644
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -41,6 +41,30 @@ static int panthor_gpu_coherency_init(struct panthor_device *ptdev)
 	return -ENOTSUPP;
 }
 
+static int panthor_gpu_asn_hash_init(struct panthor_device *ptdev)
+{
+	int ret;
+
+	ret = of_property_read_u32_array(ptdev->base.dev->of_node, "asn-hash",
+					 ptdev->asn_hash,
+					 ARRAY_SIZE(ptdev->asn_hash));
+	if (ret) {
+		if (ret == -EINVAL)
+			ret = 0;
+		return ret;
+	}
+
+	if (GPU_ARCH_MAJOR(ptdev->gpu_info.gpu_id) < 11) {
+		drm_err(&ptdev->base,
+			"Custom ASN hash not supported by the device");
+		return -EOPNOTSUPP;
+	}
+
+	ptdev->has_asn_hash = true;
+
+	return 0;
+}
+
 static int panthor_clk_init(struct panthor_device *ptdev)
 {
 	ptdev->clks.core = devm_clk_get(ptdev->base.dev, NULL);
@@ -257,6 +281,10 @@ int panthor_device_init(struct panthor_device *ptdev)
 	if (ret)
 		goto err_unplug_gpu;
 
+	ret = panthor_gpu_asn_hash_init(ptdev);
+	if (ret)
+		goto err_unplug_gpu;
+
 	ret = panthor_mmu_init(ptdev);
 	if (ret)
 		goto err_unplug_gpu;
diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
index 4fc7cf2aeed57..6f8e2b3b037e5 100644
--- a/drivers/gpu/drm/panthor/panthor_device.h
+++ b/drivers/gpu/drm/panthor/panthor_device.h
@@ -114,6 +114,12 @@ struct panthor_device {
 	/** @coherent: True if the CPU/GPU are memory coherent. */
 	bool coherent;
 
+	/** @has_asn_hash: True if custom ASN hash is enabled. */
+	bool has_asn_hash;
+
+	/** @asn_hash: ASN_HASH values for custom ASN hash */
+	u32 asn_hash[3];
+
 	/** @gpu_info: GPU information. */
 	struct drm_panthor_gpu_info gpu_info;
 
diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
index db69449a5be09..f9222b67f314d 100644
--- a/drivers/gpu/drm/panthor/panthor_gpu.c
+++ b/drivers/gpu/drm/panthor/panthor_gpu.c
@@ -52,6 +52,22 @@ static void panthor_gpu_coherency_set(struct panthor_device *ptdev)
 		ptdev->coherent ? GPU_COHERENCY_PROT_BIT(ACE_LITE) : GPU_COHERENCY_NONE);
 }
 
+static void panthor_gpu_asn_hash_set(struct panthor_device *ptdev)
+{
+	u32 l2_config;
+	u32 i;
+
+	if (!ptdev->has_asn_hash)
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(ptdev->asn_hash); i++)
+		gpu_write(ptdev, ASN_HASH(i), ptdev->asn_hash[i]);
+
+	l2_config = gpu_read(ptdev, L2_CONFIG);
+	l2_config |= L2_CONFIG_ASN_HASH_ENABLE;
+	gpu_write(ptdev, L2_CONFIG, l2_config);
+}
+
 static void panthor_gpu_irq_handler(struct panthor_device *ptdev, u32 status)
 {
 	gpu_write(ptdev, GPU_INT_CLEAR, status);
@@ -243,6 +259,7 @@ int panthor_gpu_l2_power_on(struct panthor_device *ptdev)
 
 	/* Set the desired coherency mode before the power up of L2 */
 	panthor_gpu_coherency_set(ptdev);
+	panthor_gpu_asn_hash_set(ptdev);
 
 	return panthor_gpu_power_on(ptdev, L2, 1, 20000);
 }
diff --git a/drivers/gpu/drm/panthor/panthor_regs.h b/drivers/gpu/drm/panthor/panthor_regs.h
index 8bee76d01bf83..c9f795624e79b 100644
--- a/drivers/gpu/drm/panthor/panthor_regs.h
+++ b/drivers/gpu/drm/panthor/panthor_regs.h
@@ -64,6 +64,8 @@
 
 #define GPU_FAULT_STATUS				0x3C
 #define GPU_FAULT_ADDR					0x40
+#define L2_CONFIG					0x48
+#define   L2_CONFIG_ASN_HASH_ENABLE			BIT(24)
 
 #define GPU_PWR_KEY					0x50
 #define  GPU_PWR_KEY_UNLOCK				0x2968A819
@@ -110,6 +112,8 @@
 
 #define GPU_REVID					0x280
 
+#define ASN_HASH(n)					(0x2C0 + ((n) * 4))
+
 #define GPU_COHERENCY_FEATURES				0x300
 #define GPU_COHERENCY_PROT_BIT(name)			BIT(GPU_COHERENCY_  ## name)
 
-- 
2.51.0.318.gd7df087d1a-goog

Re: [PATCH 1/2] dt-bindings: gpu: mali-valhall-csf: add asn-hash

[Boris Brezillon]

On Thu, 28 Aug 2025 13:18:05 -0700
Chia-I Wu <olvaffe@gmail.com> wrote:

> The values are written to ASN_HASH[0..2] registers. The property is
> called "l2-hash-values" in the downstream driver.
> 
> Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
> ---
>  .../devicetree/bindings/gpu/arm,mali-valhall-csf.yaml     | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> index a5b4e00217587..258bcba66d1d1 100644
> --- a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> +++ b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> @@ -85,6 +85,14 @@ properties:
>  
>    dma-coherent: true
>  
> +  asn-hash:
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    description:
> +      The values are written to ASN_HASH[0..2] registers. They affect how
> +      physical addresses are mapped to L2 cache slices.

If this is per-SoC integration details, I would hide that behind the
compatible string and have some panthor_soc_data attached to the
of_device_id entries.

> +    minItems: 3
> +    maxItems: 3
> +
>  required:
>    - compatible
>    - reg

Re: [PATCH 0/2] drm/panthor: add custom ASN hash support

[Steven Price]

On 28/08/2025 21:18, Chia-I Wu wrote:
> Some socs such as mt8196 require custom ASN hash.

I don't know the full details of this, but I'm puzzled by the "require"
here.

AIUI the "custom ASN hash support" (or L2C_SLICE_HASH as it was renamed)
affects the efficiency of the L2 caches in the GPU. It basically
determines how addresses are striped over the individual caches.

So (unless there is a specific errata) not setting a custom hash will
work just fine, but the performance might be slightly reduced.

kbase provides both a DT option and a module parameter which can be used
to override the defaults (although the parameter descriptions say "for
testing" which I think is somewhat telling).

How we should describe this somewhat depends on whether this is a
specific workaround for a SoC - in which case Boris's suggestion of
using a different compatible string and panthor_soc_data seems like a
good choice. Or if this is exposed as a general "tuning" parameter, in
which case this might be appropriate.

I believe the tuning is related to more than just a SoC (the external
memory system has an impact). So I guess a DT level knob makes most
sense here.

Steve

> Chia-I Wu (2):
>   dt-bindings: gpu: mali-valhall-csf: add asn-hash
>   drm/panthor: add asn-hash support
> 
>  .../bindings/gpu/arm,mali-valhall-csf.yaml    |  8 ++++++
>  drivers/gpu/drm/panthor/panthor_device.c      | 28 +++++++++++++++++++
>  drivers/gpu/drm/panthor/panthor_device.h      |  6 ++++
>  drivers/gpu/drm/panthor/panthor_gpu.c         | 17 +++++++++++
>  drivers/gpu/drm/panthor/panthor_regs.h        |  4 +++
>  5 files changed, 63 insertions(+)
> 

Re: [PATCH 2/2] drm/panthor: add asn-hash support

[Steven Price]

On 28/08/2025 21:18, Chia-I Wu wrote:
> Parse asn-hash and enable custom ASN hash when the property exists.
> This is required on some socs such as mt8196.
> 
> Signed-off-by: Chia-I Wu <olvaffe@gmail.com>

This mostly looks fine, although there is a question of naming. This was
renamed in a later version of the architecture to be L2C_SLICE_HASH
(rather than ASN_HASH).

I'm honestly not sure whether to stick with asn-hash (as it's out in the
wild already) or try to align with the newer spec and whether that will
create or avoid confusion!

> ---
>  drivers/gpu/drm/panthor/panthor_device.c | 28 ++++++++++++++++++++++++
>  drivers/gpu/drm/panthor/panthor_device.h |  6 +++++
>  drivers/gpu/drm/panthor/panthor_gpu.c    | 17 ++++++++++++++
>  drivers/gpu/drm/panthor/panthor_regs.h   |  4 ++++
>  4 files changed, 55 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
> index 81df49880bd87..19423c495d8d7 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.c
> +++ b/drivers/gpu/drm/panthor/panthor_device.c
> @@ -41,6 +41,30 @@ static int panthor_gpu_coherency_init(struct panthor_device *ptdev)
>  	return -ENOTSUPP;
>  }
>  
> +static int panthor_gpu_asn_hash_init(struct panthor_device *ptdev)
> +{
> +	int ret;
> +
> +	ret = of_property_read_u32_array(ptdev->base.dev->of_node, "asn-hash",
> +					 ptdev->asn_hash,
> +					 ARRAY_SIZE(ptdev->asn_hash));
> +	if (ret) {
> +		if (ret == -EINVAL)
> +			ret = 0;
> +		return ret;
> +	}

NIT: I think this would be neater written as:

	if (ret == -EINVAL)
		return 0;
	else if (ret)
		return ret

Thanks,
Steve

> +
> +	if (GPU_ARCH_MAJOR(ptdev->gpu_info.gpu_id) < 11) {
> +		drm_err(&ptdev->base,
> +			"Custom ASN hash not supported by the device");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	ptdev->has_asn_hash = true;
> +
> +	return 0;
> +}
> +
>  static int panthor_clk_init(struct panthor_device *ptdev)
>  {
>  	ptdev->clks.core = devm_clk_get(ptdev->base.dev, NULL);
> @@ -257,6 +281,10 @@ int panthor_device_init(struct panthor_device *ptdev)
>  	if (ret)
>  		goto err_unplug_gpu;
>  
> +	ret = panthor_gpu_asn_hash_init(ptdev);
> +	if (ret)
> +		goto err_unplug_gpu;
> +
>  	ret = panthor_mmu_init(ptdev);
>  	if (ret)
>  		goto err_unplug_gpu;
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index 4fc7cf2aeed57..6f8e2b3b037e5 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -114,6 +114,12 @@ struct panthor_device {
>  	/** @coherent: True if the CPU/GPU are memory coherent. */
>  	bool coherent;
>  
> +	/** @has_asn_hash: True if custom ASN hash is enabled. */
> +	bool has_asn_hash;
> +
> +	/** @asn_hash: ASN_HASH values for custom ASN hash */
> +	u32 asn_hash[3];
> +
>  	/** @gpu_info: GPU information. */
>  	struct drm_panthor_gpu_info gpu_info;
>  
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
> index db69449a5be09..f9222b67f314d 100644
> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
> @@ -52,6 +52,22 @@ static void panthor_gpu_coherency_set(struct panthor_device *ptdev)
>  		ptdev->coherent ? GPU_COHERENCY_PROT_BIT(ACE_LITE) : GPU_COHERENCY_NONE);
>  }
>  
> +static void panthor_gpu_asn_hash_set(struct panthor_device *ptdev)
> +{
> +	u32 l2_config;
> +	u32 i;
> +
> +	if (!ptdev->has_asn_hash)
> +		return;
> +
> +	for (i = 0; i < ARRAY_SIZE(ptdev->asn_hash); i++)
> +		gpu_write(ptdev, ASN_HASH(i), ptdev->asn_hash[i]);
> +
> +	l2_config = gpu_read(ptdev, L2_CONFIG);
> +	l2_config |= L2_CONFIG_ASN_HASH_ENABLE;
> +	gpu_write(ptdev, L2_CONFIG, l2_config);
> +}
> +
>  static void panthor_gpu_irq_handler(struct panthor_device *ptdev, u32 status)
>  {
>  	gpu_write(ptdev, GPU_INT_CLEAR, status);
> @@ -243,6 +259,7 @@ int panthor_gpu_l2_power_on(struct panthor_device *ptdev)
>  
>  	/* Set the desired coherency mode before the power up of L2 */
>  	panthor_gpu_coherency_set(ptdev);
> +	panthor_gpu_asn_hash_set(ptdev);
>  
>  	return panthor_gpu_power_on(ptdev, L2, 1, 20000);
>  }
> diff --git a/drivers/gpu/drm/panthor/panthor_regs.h b/drivers/gpu/drm/panthor/panthor_regs.h
> index 8bee76d01bf83..c9f795624e79b 100644
> --- a/drivers/gpu/drm/panthor/panthor_regs.h
> +++ b/drivers/gpu/drm/panthor/panthor_regs.h
> @@ -64,6 +64,8 @@
>  
>  #define GPU_FAULT_STATUS				0x3C
>  #define GPU_FAULT_ADDR					0x40
> +#define L2_CONFIG					0x48
> +#define   L2_CONFIG_ASN_HASH_ENABLE			BIT(24)
>  
>  #define GPU_PWR_KEY					0x50
>  #define  GPU_PWR_KEY_UNLOCK				0x2968A819
> @@ -110,6 +112,8 @@
>  
>  #define GPU_REVID					0x280
>  
> +#define ASN_HASH(n)					(0x2C0 + ((n) * 4))
> +
>  #define GPU_COHERENCY_FEATURES				0x300
>  #define GPU_COHERENCY_PROT_BIT(name)			BIT(GPU_COHERENCY_  ## name)
>  

Re: [PATCH 1/2] dt-bindings: gpu: mali-valhall-csf: add asn-hash

[Krzysztof Kozlowski]

On 28/08/2025 22:18, Chia-I Wu wrote:
> The values are written to ASN_HASH[0..2] registers. The property is
> called "l2-hash-values" in the downstream driver.

We don't add properties based on downstream drivers. Please provide some
sort of rationale, including explanation why this is not SoC/compatible
specific.

> 
> Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
> ---
>  .../devicetree/bindings/gpu/arm,mali-valhall-csf.yaml     | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> index a5b4e00217587..258bcba66d1d1 100644
> --- a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> +++ b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> @@ -85,6 +85,14 @@ properties:
>  
>    dma-coherent: true
>  
> +  asn-hash:

Missing vendor prefix or please explain which common schema has it
already defined.


Best regards,
Krzysztof

Re: [PATCH 0/2] drm/panthor: add custom ASN hash support

[Chia-I Wu]

On Fri, Aug 29, 2025 at 6:41 AM Steven Price <steven.price@arm.com> wrote:
>
> On 28/08/2025 21:18, Chia-I Wu wrote:
> > Some socs such as mt8196 require custom ASN hash.
>
> I don't know the full details of this, but I'm puzzled by the "require"
> here.
>
> AIUI the "custom ASN hash support" (or L2C_SLICE_HASH as it was renamed)
> affects the efficiency of the L2 caches in the GPU. It basically
> determines how addresses are striped over the individual caches.
>
> So (unless there is a specific errata) not setting a custom hash will
> work just fine, but the performance might be slightly reduced.
All memory access results in faults unless custom ASN hash is enabled on mt8196.

It sounds like this is a soc-specific quirk.  I will check with the
vendor, and likely turn this into a quirk.

>
> kbase provides both a DT option and a module parameter which can be used
> to override the defaults (although the parameter descriptions say "for
> testing" which I think is somewhat telling).
>
> How we should describe this somewhat depends on whether this is a
> specific workaround for a SoC - in which case Boris's suggestion of
> using a different compatible string and panthor_soc_data seems like a
> good choice. Or if this is exposed as a general "tuning" parameter, in
> which case this might be appropriate.
>
> I believe the tuning is related to more than just a SoC (the external
> memory system has an impact). So I guess a DT level knob makes most
> sense here.
>
> Steve
>
> > Chia-I Wu (2):
> >   dt-bindings: gpu: mali-valhall-csf: add asn-hash
> >   drm/panthor: add asn-hash support
> >
> >  .../bindings/gpu/arm,mali-valhall-csf.yaml    |  8 ++++++
> >  drivers/gpu/drm/panthor/panthor_device.c      | 28 +++++++++++++++++++
> >  drivers/gpu/drm/panthor/panthor_device.h      |  6 ++++
> >  drivers/gpu/drm/panthor/panthor_gpu.c         | 17 +++++++++++
> >  drivers/gpu/drm/panthor/panthor_regs.h        |  4 +++
> >  5 files changed, 63 insertions(+)
> >
>