[PATCH v4 0/3] Determine the number of DMA channels by 'dma-channels' property

[PATCH v4 0/3] Determine the number of DMA channels by 'dma-channels' property

[Zong Li]

The PDMA driver currently assumes there are four channels by default, it
might cause the error if there is actually less than four channels.
Change that by getting number of channel dynamically from device tree.
For backwards-compatible, it uses the default value (i.e. 4) when there
is no 'dma-channels' information in dts.

This patch set contains the dts and dt-bindings change.

Changed in v4:
 - Remove cflags of debug use reported-by: kernel test robot <lkp@intel.com>

Changed in v3:
 - Fix allocating wrong size
 - Return error if 'dma-channels' is larger than maximum

Changed in v2:
 - Rebase on tag v5.16
 - Use 4 as default value of dma-channels

Zong Li (3):
  riscv: dts: Add dma-channels property in dma node
  dt-bindings: Add dma-channels for pdma device node
  dmaengine: sf-pdma: Get number of channel by device tree

 .../bindings/dma/sifive,fu540-c000-pdma.yaml  |  7 +++++++
 .../boot/dts/microchip/microchip-mpfs.dtsi    |  1 +
 arch/riscv/boot/dts/sifive/fu540-c000.dtsi    |  1 +
 drivers/dma/sf-pdma/sf-pdma.c                 | 20 ++++++++++++-------
 drivers/dma/sf-pdma/sf-pdma.h                 |  8 ++------
 5 files changed, 24 insertions(+), 13 deletions(-)

-- 
2.31.1

[PATCH v4 0/3] Determine the number of DMA channels by 'dma-channels' property

[Zong Li]

The PDMA driver currently assumes there are four channels by default, it
might cause the error if there is actually less than four channels.
Change that by getting number of channel dynamically from device tree.
For backwards-compatible, it uses the default value (i.e. 4) when there
is no 'dma-channels' information in dts.

This patch set contains the dts and dt-bindings change.

Changed in v4:
 - Remove cflags of debug use reported-by: kernel test robot <lkp@intel.com>

Changed in v3:
 - Fix allocating wrong size
 - Return error if 'dma-channels' is larger than maximum

Changed in v2:
 - Rebase on tag v5.16
 - Use 4 as default value of dma-channels

Zong Li (3):
  riscv: dts: Add dma-channels property in dma node
  dt-bindings: Add dma-channels for pdma device node
  dmaengine: sf-pdma: Get number of channel by device tree

 .../bindings/dma/sifive,fu540-c000-pdma.yaml  |  7 +++++++
 .../boot/dts/microchip/microchip-mpfs.dtsi    |  1 +
 arch/riscv/boot/dts/sifive/fu540-c000.dtsi    |  1 +
 drivers/dma/sf-pdma/sf-pdma.c                 | 20 ++++++++++++-------
 drivers/dma/sf-pdma/sf-pdma.h                 |  8 ++------
 5 files changed, 24 insertions(+), 13 deletions(-)

-- 
2.31.1


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[PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Zong Li]

Add dma-channels property, then we can determine how many channels there
by device tree.

Signed-off-by: Zong Li <zong.li@sifive.com>
---
 arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
 arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
index c9f6d205d2ba..3c48f2d7a4a4 100644
--- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
+++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
@@ -188,6 +188,7 @@ dma@3000000 {
 			reg = <0x0 0x3000000 0x0 0x8000>;
 			interrupt-parent = <&plic>;
 			interrupts = <23 24 25 26 27 28 29 30>;
+			dma-channels = <4>;
 			#dma-cells = <1>;
 		};
 
diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
index 0655b5c4201d..2bdfe7f06e4b 100644
--- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
+++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
@@ -171,6 +171,7 @@ dma: dma@3000000 {
 			reg = <0x0 0x3000000 0x0 0x8000>;
 			interrupt-parent = <&plic0>;
 			interrupts = <23 24 25 26 27 28 29 30>;
+			dma-channels = <4>;
 			#dma-cells = <1>;
 		};
 		uart1: serial@10011000 {
-- 
2.31.1

[PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Zong Li]

Add dma-channels property, then we can determine how many channels there
by device tree.

Signed-off-by: Zong Li <zong.li@sifive.com>
---
 arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
 arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
index c9f6d205d2ba..3c48f2d7a4a4 100644
--- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
+++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
@@ -188,6 +188,7 @@ dma@3000000 {
 			reg = <0x0 0x3000000 0x0 0x8000>;
 			interrupt-parent = <&plic>;
 			interrupts = <23 24 25 26 27 28 29 30>;
+			dma-channels = <4>;
 			#dma-cells = <1>;
 		};
 
diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
index 0655b5c4201d..2bdfe7f06e4b 100644
--- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
+++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
@@ -171,6 +171,7 @@ dma: dma@3000000 {
 			reg = <0x0 0x3000000 0x0 0x8000>;
 			interrupt-parent = <&plic0>;
 			interrupts = <23 24 25 26 27 28 29 30>;
+			dma-channels = <4>;
 			#dma-cells = <1>;
 		};
 		uart1: serial@10011000 {
-- 
2.31.1


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[PATCH v4 2/3] dt-bindings: Add dma-channels for pdma device node

[Zong Li]

Add dma-channels property, then we can determine how many channels there
by device tree, rather than statically defines it in PDMA driver

Signed-off-by: Zong Li <zong.li@sifive.com>
---
 .../devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml    | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
index d32a71b975fe..3dbb8caefc17 100644
--- a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
+++ b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
@@ -34,6 +34,12 @@ properties:
     minItems: 1
     maxItems: 8
 
+  dma-channels:
+    description: For backwards-compatible, the default value is 4
+    minimum: 1
+    maximum: 4
+    default: 4
+
   '#dma-cells':
     const: 1
 
@@ -50,6 +56,7 @@ examples:
     dma@3000000 {
       compatible = "sifive,fu540-c000-pdma";
       reg = <0x3000000 0x8000>;
+      dma-channels = <4>;
       interrupts = <23 24 25 26 27 28 29 30>;
       #dma-cells = <1>;
     };
-- 
2.31.1

[PATCH v4 2/3] dt-bindings: Add dma-channels for pdma device node

[Zong Li]

Add dma-channels property, then we can determine how many channels there
by device tree, rather than statically defines it in PDMA driver

Signed-off-by: Zong Li <zong.li@sifive.com>
---
 .../devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml    | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
index d32a71b975fe..3dbb8caefc17 100644
--- a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
+++ b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
@@ -34,6 +34,12 @@ properties:
     minItems: 1
     maxItems: 8
 
+  dma-channels:
+    description: For backwards-compatible, the default value is 4
+    minimum: 1
+    maximum: 4
+    default: 4
+
   '#dma-cells':
     const: 1
 
@@ -50,6 +56,7 @@ examples:
     dma@3000000 {
       compatible = "sifive,fu540-c000-pdma";
       reg = <0x3000000 0x8000>;
+      dma-channels = <4>;
       interrupts = <23 24 25 26 27 28 29 30>;
       #dma-cells = <1>;
     };
-- 
2.31.1


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[PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

It currently assumes that there are always four channels, it would
cause the error if there is actually less than four channels. Change
that by getting number of channel from device tree.

For backwards-compatible, it uses the default value (i.e. 4) when there
is no 'dma-channels' information in dts.

Signed-off-by: Zong Li <zong.li@sifive.com>
---
 drivers/dma/sf-pdma/sf-pdma.c | 20 +++++++++++++-------
 drivers/dma/sf-pdma/sf-pdma.h |  8 ++------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
index f12606aeff87..1264add9897e 100644
--- a/drivers/dma/sf-pdma/sf-pdma.c
+++ b/drivers/dma/sf-pdma/sf-pdma.c
@@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
 static int sf_pdma_probe(struct platform_device *pdev)
 {
 	struct sf_pdma *pdma;
-	struct sf_pdma_chan *chan;
 	struct resource *res;
-	int len, chans;
 	int ret;
 	const enum dma_slave_buswidth widths =
 		DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
@@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
 		DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
 		DMA_SLAVE_BUSWIDTH_64_BYTES;
 
-	chans = PDMA_NR_CH;
-	len = sizeof(*pdma) + sizeof(*chan) * chans;
-	pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
+	pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
 	if (!pdma)
 		return -ENOMEM;
 
-	pdma->n_chans = chans;
+	ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
+				   &pdma->n_chans);
+	if (ret) {
+		dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
+		pdma->n_chans = PDMA_MAX_NR_CH;
+	}
+
+	if (pdma->n_chans > PDMA_MAX_NR_CH) {
+		dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
+		return -EINVAL;
+	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	pdma->membase = devm_ioremap_resource(&pdev->dev, res);
@@ -556,7 +562,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
 	struct sf_pdma_chan *ch;
 	int i;
 
-	for (i = 0; i < PDMA_NR_CH; i++) {
+	for (i = 0; i < pdma->n_chans; i++) {
 		ch = &pdma->chans[i];
 
 		devm_free_irq(&pdev->dev, ch->txirq, ch);
diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
index 0c20167b097d..8127d792f639 100644
--- a/drivers/dma/sf-pdma/sf-pdma.h
+++ b/drivers/dma/sf-pdma/sf-pdma.h
@@ -22,11 +22,7 @@
 #include "../dmaengine.h"
 #include "../virt-dma.h"
 
-#define PDMA_NR_CH					4
-
-#if (PDMA_NR_CH != 4)
-#error "Please define PDMA_NR_CH to 4"
-#endif
+#define PDMA_MAX_NR_CH					4
 
 #define PDMA_BASE_ADDR					0x3000000
 #define PDMA_CHAN_OFFSET				0x1000
@@ -118,7 +114,7 @@ struct sf_pdma {
 	void __iomem            *membase;
 	void __iomem            *mappedbase;
 	u32			n_chans;
-	struct sf_pdma_chan	chans[PDMA_NR_CH];
+	struct sf_pdma_chan	chans[PDMA_MAX_NR_CH];
 };
 
 #endif /* _SF_PDMA_H */
-- 
2.31.1

[PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

It currently assumes that there are always four channels, it would
cause the error if there is actually less than four channels. Change
that by getting number of channel from device tree.

For backwards-compatible, it uses the default value (i.e. 4) when there
is no 'dma-channels' information in dts.

Signed-off-by: Zong Li <zong.li@sifive.com>
---
 drivers/dma/sf-pdma/sf-pdma.c | 20 +++++++++++++-------
 drivers/dma/sf-pdma/sf-pdma.h |  8 ++------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
index f12606aeff87..1264add9897e 100644
--- a/drivers/dma/sf-pdma/sf-pdma.c
+++ b/drivers/dma/sf-pdma/sf-pdma.c
@@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
 static int sf_pdma_probe(struct platform_device *pdev)
 {
 	struct sf_pdma *pdma;
-	struct sf_pdma_chan *chan;
 	struct resource *res;
-	int len, chans;
 	int ret;
 	const enum dma_slave_buswidth widths =
 		DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
@@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
 		DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
 		DMA_SLAVE_BUSWIDTH_64_BYTES;
 
-	chans = PDMA_NR_CH;
-	len = sizeof(*pdma) + sizeof(*chan) * chans;
-	pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
+	pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
 	if (!pdma)
 		return -ENOMEM;
 
-	pdma->n_chans = chans;
+	ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
+				   &pdma->n_chans);
+	if (ret) {
+		dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
+		pdma->n_chans = PDMA_MAX_NR_CH;
+	}
+
+	if (pdma->n_chans > PDMA_MAX_NR_CH) {
+		dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
+		return -EINVAL;
+	}
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	pdma->membase = devm_ioremap_resource(&pdev->dev, res);
@@ -556,7 +562,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
 	struct sf_pdma_chan *ch;
 	int i;
 
-	for (i = 0; i < PDMA_NR_CH; i++) {
+	for (i = 0; i < pdma->n_chans; i++) {
 		ch = &pdma->chans[i];
 
 		devm_free_irq(&pdev->dev, ch->txirq, ch);
diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
index 0c20167b097d..8127d792f639 100644
--- a/drivers/dma/sf-pdma/sf-pdma.h
+++ b/drivers/dma/sf-pdma/sf-pdma.h
@@ -22,11 +22,7 @@
 #include "../dmaengine.h"
 #include "../virt-dma.h"
 
-#define PDMA_NR_CH					4
-
-#if (PDMA_NR_CH != 4)
-#error "Please define PDMA_NR_CH to 4"
-#endif
+#define PDMA_MAX_NR_CH					4
 
 #define PDMA_BASE_ADDR					0x3000000
 #define PDMA_CHAN_OFFSET				0x1000
@@ -118,7 +114,7 @@ struct sf_pdma {
 	void __iomem            *membase;
 	void __iomem            *mappedbase;
 	u32			n_chans;
-	struct sf_pdma_chan	chans[PDMA_NR_CH];
+	struct sf_pdma_chan	chans[PDMA_MAX_NR_CH];
 };
 
 #endif /* _SF_PDMA_H */
-- 
2.31.1


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Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Conor.Dooley]

On 17/01/2022 01:35, Zong Li wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Add dma-channels property, then we can determine how many channels there
> by device tree.
> 
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>   arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
>   arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
>   2 files changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> index c9f6d205d2ba..3c48f2d7a4a4 100644
> --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> @@ -188,6 +188,7 @@ dma@3000000 {
>                          reg = <0x0 0x3000000 0x0 0x8000>;
>                          interrupt-parent = <&plic>;
>                          interrupts = <23 24 25 26 27 28 29 30>;
> +                       dma-channels = <4>;
>                          #dma-cells = <1>;
>                  };
For mpfs: Acked-by: Conor Dooley <conor.dooley@microchip.com>

> 
> diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> index 0655b5c4201d..2bdfe7f06e4b 100644
> --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> @@ -171,6 +171,7 @@ dma: dma@3000000 {
>                          reg = <0x0 0x3000000 0x0 0x8000>;
>                          interrupt-parent = <&plic0>;
>                          interrupts = <23 24 25 26 27 28 29 30>;
> +                       dma-channels = <4>;
>                          #dma-cells = <1>;
>                  };
>                  uart1: serial@10011000 {
> --
> 2.31.1
> 

Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Conor.Dooley]

On 17/01/2022 01:35, Zong Li wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Add dma-channels property, then we can determine how many channels there
> by device tree.
> 
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>   arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
>   arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
>   2 files changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> index c9f6d205d2ba..3c48f2d7a4a4 100644
> --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> @@ -188,6 +188,7 @@ dma@3000000 {
>                          reg = <0x0 0x3000000 0x0 0x8000>;
>                          interrupt-parent = <&plic>;
>                          interrupts = <23 24 25 26 27 28 29 30>;
> +                       dma-channels = <4>;
>                          #dma-cells = <1>;
>                  };
For mpfs: Acked-by: Conor Dooley <conor.dooley@microchip.com>

> 
> diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> index 0655b5c4201d..2bdfe7f06e4b 100644
> --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> @@ -171,6 +171,7 @@ dma: dma@3000000 {
>                          reg = <0x0 0x3000000 0x0 0x8000>;
>                          interrupt-parent = <&plic0>;
>                          interrupts = <23 24 25 26 27 28 29 30>;
> +                       dma-channels = <4>;
>                          #dma-cells = <1>;
>                  };
>                  uart1: serial@10011000 {
> --
> 2.31.1
> 

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Re: [PATCH v4 2/3] dt-bindings: Add dma-channels for pdma device node

[Palmer Dabbelt]

On Sun, 16 Jan 2022 17:35:27 PST (-0800), zong.li@sifive.com wrote:
> Add dma-channels property, then we can determine how many channels there
> by device tree, rather than statically defines it in PDMA driver

Maybe "statically defining it" is better here?

>
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  .../devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml    | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> index d32a71b975fe..3dbb8caefc17 100644
> --- a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> +++ b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> @@ -34,6 +34,12 @@ properties:
>      minItems: 1
>      maxItems: 8
>
> +  dma-channels:
> +    description: For backwards-compatible, the default value is 4

Maybe "backwards-compatibility" is better here?

> +    minimum: 1
> +    maximum: 4
> +    default: 4
> +
>    '#dma-cells':
>      const: 1
>
> @@ -50,6 +56,7 @@ examples:
>      dma@3000000 {
>        compatible = "sifive,fu540-c000-pdma";

IMO we should have a "sifive,pdma-1.0.0" (or whatever the versioning 
scheme ended up being) here, in addition to the SOC-specific DT entry.  
It's kind of odd to start extending the SOC-specific DT entry, as the 
whole idea there is to let us have an out in case we find future 
compatibility issues.

>        reg = <0x3000000 0x8000>;
> +      dma-channels = <4>;
>        interrupts = <23 24 25 26 27 28 29 30>;
>        #dma-cells = <1>;
>      };

Re: [PATCH v4 2/3] dt-bindings: Add dma-channels for pdma device node

[Palmer Dabbelt]

On Sun, 16 Jan 2022 17:35:27 PST (-0800), zong.li@sifive.com wrote:
> Add dma-channels property, then we can determine how many channels there
> by device tree, rather than statically defines it in PDMA driver

Maybe "statically defining it" is better here?

>
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  .../devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml    | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> index d32a71b975fe..3dbb8caefc17 100644
> --- a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> +++ b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> @@ -34,6 +34,12 @@ properties:
>      minItems: 1
>      maxItems: 8
>
> +  dma-channels:
> +    description: For backwards-compatible, the default value is 4

Maybe "backwards-compatibility" is better here?

> +    minimum: 1
> +    maximum: 4
> +    default: 4
> +
>    '#dma-cells':
>      const: 1
>
> @@ -50,6 +56,7 @@ examples:
>      dma@3000000 {
>        compatible = "sifive,fu540-c000-pdma";

IMO we should have a "sifive,pdma-1.0.0" (or whatever the versioning 
scheme ended up being) here, in addition to the SOC-specific DT entry.  
It's kind of odd to start extending the SOC-specific DT entry, as the 
whole idea there is to let us have an out in case we find future 
compatibility issues.

>        reg = <0x3000000 0x8000>;
> +      dma-channels = <4>;
>        interrupts = <23 24 25 26 27 28 29 30>;
>        #dma-cells = <1>;
>      };

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Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Palmer Dabbelt]

On Sun, 16 Jan 2022 17:35:26 PST (-0800), zong.li@sifive.com wrote:
> Add dma-channels property, then we can determine how many channels there
> by device tree.
>
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
>  arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> index c9f6d205d2ba..3c48f2d7a4a4 100644
> --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> @@ -188,6 +188,7 @@ dma@3000000 {
>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>
> diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> index 0655b5c4201d..2bdfe7f06e4b 100644
> --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> @@ -171,6 +171,7 @@ dma: dma@3000000 {
>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic0>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>  		uart1: serial@10011000 {

I've got some comments in on the bindings, but I'm assuming it's easier 
to keep these all together.  Happy to take this through the RISC-V tree, 
but I'm guessing it'll be easier to take these via dmaengine as there's 
a lot more diff there so

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

Thanks!

Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Palmer Dabbelt]

On Sun, 16 Jan 2022 17:35:26 PST (-0800), zong.li@sifive.com wrote:
> Add dma-channels property, then we can determine how many channels there
> by device tree.
>
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
>  arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> index c9f6d205d2ba..3c48f2d7a4a4 100644
> --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> @@ -188,6 +188,7 @@ dma@3000000 {
>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>
> diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> index 0655b5c4201d..2bdfe7f06e4b 100644
> --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> @@ -171,6 +171,7 @@ dma: dma@3000000 {
>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic0>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>  		uart1: serial@10011000 {

I've got some comments in on the bindings, but I'm assuming it's easier 
to keep these all together.  Happy to take this through the RISC-V tree, 
but I'm guessing it'll be easier to take these via dmaengine as there's 
a lot more diff there so

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

Thanks!

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Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Palmer Dabbelt]

On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> It currently assumes that there are always four channels, it would
> cause the error if there is actually less than four channels. Change
> that by getting number of channel from device tree.
>
> For backwards-compatible, it uses the default value (i.e. 4) when there
> is no 'dma-channels' information in dts.

Some of the same wording issues here as those I pointed out in the DT 
bindings patch.

> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  drivers/dma/sf-pdma/sf-pdma.c | 20 +++++++++++++-------
>  drivers/dma/sf-pdma/sf-pdma.h |  8 ++------
>  2 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> index f12606aeff87..1264add9897e 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.c
> +++ b/drivers/dma/sf-pdma/sf-pdma.c
> @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
>  static int sf_pdma_probe(struct platform_device *pdev)
>  {
>  	struct sf_pdma *pdma;
> -	struct sf_pdma_chan *chan;
>  	struct resource *res;
> -	int len, chans;
>  	int ret;
>  	const enum dma_slave_buswidth widths =
>  		DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
>  		DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
>  		DMA_SLAVE_BUSWIDTH_64_BYTES;
>
> -	chans = PDMA_NR_CH;
> -	len = sizeof(*pdma) + sizeof(*chan) * chans;
> -	pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> +	pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
>  	if (!pdma)
>  		return -ENOMEM;
>
> -	pdma->n_chans = chans;
> +	ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> +				   &pdma->n_chans);
> +	if (ret) {
> +		dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> +		pdma->n_chans = PDMA_MAX_NR_CH;
> +	}
> +
> +	if (pdma->n_chans > PDMA_MAX_NR_CH) {
> +		dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> +		return -EINVAL;

Can we get away with just using only the number of channels the driver 
actually supports?  ie, just never sending an op to the channels above 
MAX_NR_CH?  That should leave us with nothing to track.

> +	}
>
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	pdma->membase = devm_ioremap_resource(&pdev->dev, res);
> @@ -556,7 +562,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
>  	struct sf_pdma_chan *ch;
>  	int i;
>
> -	for (i = 0; i < PDMA_NR_CH; i++) {
> +	for (i = 0; i < pdma->n_chans; i++) {
>  		ch = &pdma->chans[i];
>
>  		devm_free_irq(&pdev->dev, ch->txirq, ch);
> diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
> index 0c20167b097d..8127d792f639 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.h
> +++ b/drivers/dma/sf-pdma/sf-pdma.h
> @@ -22,11 +22,7 @@
>  #include "../dmaengine.h"
>  #include "../virt-dma.h"
>
> -#define PDMA_NR_CH					4
> -
> -#if (PDMA_NR_CH != 4)
> -#error "Please define PDMA_NR_CH to 4"
> -#endif
> +#define PDMA_MAX_NR_CH					4
>
>  #define PDMA_BASE_ADDR					0x3000000
>  #define PDMA_CHAN_OFFSET				0x1000
> @@ -118,7 +114,7 @@ struct sf_pdma {
>  	void __iomem            *membase;
>  	void __iomem            *mappedbase;
>  	u32			n_chans;
> -	struct sf_pdma_chan	chans[PDMA_NR_CH];
> +	struct sf_pdma_chan	chans[PDMA_MAX_NR_CH];
>  };
>
>  #endif /* _SF_PDMA_H */

Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Palmer Dabbelt]

On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> It currently assumes that there are always four channels, it would
> cause the error if there is actually less than four channels. Change
> that by getting number of channel from device tree.
>
> For backwards-compatible, it uses the default value (i.e. 4) when there
> is no 'dma-channels' information in dts.

Some of the same wording issues here as those I pointed out in the DT 
bindings patch.

> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  drivers/dma/sf-pdma/sf-pdma.c | 20 +++++++++++++-------
>  drivers/dma/sf-pdma/sf-pdma.h |  8 ++------
>  2 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> index f12606aeff87..1264add9897e 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.c
> +++ b/drivers/dma/sf-pdma/sf-pdma.c
> @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
>  static int sf_pdma_probe(struct platform_device *pdev)
>  {
>  	struct sf_pdma *pdma;
> -	struct sf_pdma_chan *chan;
>  	struct resource *res;
> -	int len, chans;
>  	int ret;
>  	const enum dma_slave_buswidth widths =
>  		DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
>  		DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
>  		DMA_SLAVE_BUSWIDTH_64_BYTES;
>
> -	chans = PDMA_NR_CH;
> -	len = sizeof(*pdma) + sizeof(*chan) * chans;
> -	pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> +	pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
>  	if (!pdma)
>  		return -ENOMEM;
>
> -	pdma->n_chans = chans;
> +	ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> +				   &pdma->n_chans);
> +	if (ret) {
> +		dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> +		pdma->n_chans = PDMA_MAX_NR_CH;
> +	}
> +
> +	if (pdma->n_chans > PDMA_MAX_NR_CH) {
> +		dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> +		return -EINVAL;

Can we get away with just using only the number of channels the driver 
actually supports?  ie, just never sending an op to the channels above 
MAX_NR_CH?  That should leave us with nothing to track.

> +	}
>
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	pdma->membase = devm_ioremap_resource(&pdev->dev, res);
> @@ -556,7 +562,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
>  	struct sf_pdma_chan *ch;
>  	int i;
>
> -	for (i = 0; i < PDMA_NR_CH; i++) {
> +	for (i = 0; i < pdma->n_chans; i++) {
>  		ch = &pdma->chans[i];
>
>  		devm_free_irq(&pdev->dev, ch->txirq, ch);
> diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
> index 0c20167b097d..8127d792f639 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.h
> +++ b/drivers/dma/sf-pdma/sf-pdma.h
> @@ -22,11 +22,7 @@
>  #include "../dmaengine.h"
>  #include "../virt-dma.h"
>
> -#define PDMA_NR_CH					4
> -
> -#if (PDMA_NR_CH != 4)
> -#error "Please define PDMA_NR_CH to 4"
> -#endif
> +#define PDMA_MAX_NR_CH					4
>
>  #define PDMA_BASE_ADDR					0x3000000
>  #define PDMA_CHAN_OFFSET				0x1000
> @@ -118,7 +114,7 @@ struct sf_pdma {
>  	void __iomem            *membase;
>  	void __iomem            *mappedbase;
>  	u32			n_chans;
> -	struct sf_pdma_chan	chans[PDMA_NR_CH];
> +	struct sf_pdma_chan	chans[PDMA_MAX_NR_CH];
>  };
>
>  #endif /* _SF_PDMA_H */

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Re: [PATCH v4 2/3] dt-bindings: Add dma-channels for pdma device node

[Zong Li]

On Fri, Jan 21, 2022 at 2:51 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Sun, 16 Jan 2022 17:35:27 PST (-0800), zong.li@sifive.com wrote:
> > Add dma-channels property, then we can determine how many channels there
> > by device tree, rather than statically defines it in PDMA driver
>
> Maybe "statically defining it" is better here?
>

Thanks for the correction, I would modify it in the next version.

> >
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > ---
> >  .../devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml    | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> > index d32a71b975fe..3dbb8caefc17 100644
> > --- a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> > +++ b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> > @@ -34,6 +34,12 @@ properties:
> >      minItems: 1
> >      maxItems: 8
> >
> > +  dma-channels:
> > +    description: For backwards-compatible, the default value is 4
>
> Maybe "backwards-compatibility" is better here?

Thanks, let me change it in the next version together.

>
> > +    minimum: 1
> > +    maximum: 4
> > +    default: 4
> > +
> >    '#dma-cells':
> >      const: 1
> >
> > @@ -50,6 +56,7 @@ examples:
> >      dma@3000000 {
> >        compatible = "sifive,fu540-c000-pdma";
>
> IMO we should have a "sifive,pdma-1.0.0" (or whatever the versioning
> scheme ended up being) here, in addition to the SOC-specific DT entry.
> It's kind of odd to start extending the SOC-specific DT entry, as the
> whole idea there is to let us have an out in case we find future
> compatibility issues.

yes, I notice that we usually have a entry with the version in other
device nodes, such as "sifive,xxx0", I guess we should have a
"sifive,pdma0" there, thanks for your advice, let me add it and use it
in match table of pdma driver in the next version.

>
> >        reg = <0x3000000 0x8000>;
> > +      dma-channels = <4>;
> >        interrupts = <23 24 25 26 27 28 29 30>;
> >        #dma-cells = <1>;
> >      };

Re: [PATCH v4 2/3] dt-bindings: Add dma-channels for pdma device node

[Zong Li]

On Fri, Jan 21, 2022 at 2:51 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Sun, 16 Jan 2022 17:35:27 PST (-0800), zong.li@sifive.com wrote:
> > Add dma-channels property, then we can determine how many channels there
> > by device tree, rather than statically defines it in PDMA driver
>
> Maybe "statically defining it" is better here?
>

Thanks for the correction, I would modify it in the next version.

> >
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > ---
> >  .../devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml    | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> > index d32a71b975fe..3dbb8caefc17 100644
> > --- a/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> > +++ b/Documentation/devicetree/bindings/dma/sifive,fu540-c000-pdma.yaml
> > @@ -34,6 +34,12 @@ properties:
> >      minItems: 1
> >      maxItems: 8
> >
> > +  dma-channels:
> > +    description: For backwards-compatible, the default value is 4
>
> Maybe "backwards-compatibility" is better here?

Thanks, let me change it in the next version together.

>
> > +    minimum: 1
> > +    maximum: 4
> > +    default: 4
> > +
> >    '#dma-cells':
> >      const: 1
> >
> > @@ -50,6 +56,7 @@ examples:
> >      dma@3000000 {
> >        compatible = "sifive,fu540-c000-pdma";
>
> IMO we should have a "sifive,pdma-1.0.0" (or whatever the versioning
> scheme ended up being) here, in addition to the SOC-specific DT entry.
> It's kind of odd to start extending the SOC-specific DT entry, as the
> whole idea there is to let us have an out in case we find future
> compatibility issues.

yes, I notice that we usually have a entry with the version in other
device nodes, such as "sifive,xxx0", I guess we should have a
"sifive,pdma0" there, thanks for your advice, let me add it and use it
in match table of pdma driver in the next version.

>
> >        reg = <0x3000000 0x8000>;
> > +      dma-channels = <4>;
> >        interrupts = <23 24 25 26 27 28 29 30>;
> >        #dma-cells = <1>;
> >      };

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Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > It currently assumes that there are always four channels, it would
> > cause the error if there is actually less than four channels. Change
> > that by getting number of channel from device tree.
> >
> > For backwards-compatible, it uses the default value (i.e. 4) when there
> > is no 'dma-channels' information in dts.
>
> Some of the same wording issues here as those I pointed out in the DT
> bindings patch.
>
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > ---
> >  drivers/dma/sf-pdma/sf-pdma.c | 20 +++++++++++++-------
> >  drivers/dma/sf-pdma/sf-pdma.h |  8 ++------
> >  2 files changed, 15 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> > index f12606aeff87..1264add9897e 100644
> > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> >  static int sf_pdma_probe(struct platform_device *pdev)
> >  {
> >       struct sf_pdma *pdma;
> > -     struct sf_pdma_chan *chan;
> >       struct resource *res;
> > -     int len, chans;
> >       int ret;
> >       const enum dma_slave_buswidth widths =
> >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> >
> > -     chans = PDMA_NR_CH;
> > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> >       if (!pdma)
> >               return -ENOMEM;
> >
> > -     pdma->n_chans = chans;
> > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > +                                &pdma->n_chans);
> > +     if (ret) {
> > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > +     }
> > +
> > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > +             return -EINVAL;
>
> Can we get away with just using only the number of channels the driver
> actually supports?  ie, just never sending an op to the channels above
> MAX_NR_CH?  That should leave us with nothing to track.

It might be a bit like when pdma->n_chans is bigger than the maximum,
set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
don't access the channels above the maximum. If I understand
correctly, I gave the similar thought in the thread of v2 patch, and
there are some discussions on that, but this way seems to lead to
hard-to-track problems.

>
> > +     }
> >
> >       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >       pdma->membase = devm_ioremap_resource(&pdev->dev, res);
> > @@ -556,7 +562,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
> >       struct sf_pdma_chan *ch;
> >       int i;
> >
> > -     for (i = 0; i < PDMA_NR_CH; i++) {
> > +     for (i = 0; i < pdma->n_chans; i++) {
> >               ch = &pdma->chans[i];
> >
> >               devm_free_irq(&pdev->dev, ch->txirq, ch);
> > diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
> > index 0c20167b097d..8127d792f639 100644
> > --- a/drivers/dma/sf-pdma/sf-pdma.h
> > +++ b/drivers/dma/sf-pdma/sf-pdma.h
> > @@ -22,11 +22,7 @@
> >  #include "../dmaengine.h"
> >  #include "../virt-dma.h"
> >
> > -#define PDMA_NR_CH                                   4
> > -
> > -#if (PDMA_NR_CH != 4)
> > -#error "Please define PDMA_NR_CH to 4"
> > -#endif
> > +#define PDMA_MAX_NR_CH                                       4
> >
> >  #define PDMA_BASE_ADDR                                       0x3000000
> >  #define PDMA_CHAN_OFFSET                             0x1000
> > @@ -118,7 +114,7 @@ struct sf_pdma {
> >       void __iomem            *membase;
> >       void __iomem            *mappedbase;
> >       u32                     n_chans;
> > -     struct sf_pdma_chan     chans[PDMA_NR_CH];
> > +     struct sf_pdma_chan     chans[PDMA_MAX_NR_CH];
> >  };
> >
> >  #endif /* _SF_PDMA_H */

Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > It currently assumes that there are always four channels, it would
> > cause the error if there is actually less than four channels. Change
> > that by getting number of channel from device tree.
> >
> > For backwards-compatible, it uses the default value (i.e. 4) when there
> > is no 'dma-channels' information in dts.
>
> Some of the same wording issues here as those I pointed out in the DT
> bindings patch.
>
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > ---
> >  drivers/dma/sf-pdma/sf-pdma.c | 20 +++++++++++++-------
> >  drivers/dma/sf-pdma/sf-pdma.h |  8 ++------
> >  2 files changed, 15 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> > index f12606aeff87..1264add9897e 100644
> > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> >  static int sf_pdma_probe(struct platform_device *pdev)
> >  {
> >       struct sf_pdma *pdma;
> > -     struct sf_pdma_chan *chan;
> >       struct resource *res;
> > -     int len, chans;
> >       int ret;
> >       const enum dma_slave_buswidth widths =
> >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> >
> > -     chans = PDMA_NR_CH;
> > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> >       if (!pdma)
> >               return -ENOMEM;
> >
> > -     pdma->n_chans = chans;
> > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > +                                &pdma->n_chans);
> > +     if (ret) {
> > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > +     }
> > +
> > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > +             return -EINVAL;
>
> Can we get away with just using only the number of channels the driver
> actually supports?  ie, just never sending an op to the channels above
> MAX_NR_CH?  That should leave us with nothing to track.

It might be a bit like when pdma->n_chans is bigger than the maximum,
set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
don't access the channels above the maximum. If I understand
correctly, I gave the similar thought in the thread of v2 patch, and
there are some discussions on that, but this way seems to lead to
hard-to-track problems.

>
> > +     }
> >
> >       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >       pdma->membase = devm_ioremap_resource(&pdev->dev, res);
> > @@ -556,7 +562,7 @@ static int sf_pdma_remove(struct platform_device *pdev)
> >       struct sf_pdma_chan *ch;
> >       int i;
> >
> > -     for (i = 0; i < PDMA_NR_CH; i++) {
> > +     for (i = 0; i < pdma->n_chans; i++) {
> >               ch = &pdma->chans[i];
> >
> >               devm_free_irq(&pdev->dev, ch->txirq, ch);
> > diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
> > index 0c20167b097d..8127d792f639 100644
> > --- a/drivers/dma/sf-pdma/sf-pdma.h
> > +++ b/drivers/dma/sf-pdma/sf-pdma.h
> > @@ -22,11 +22,7 @@
> >  #include "../dmaengine.h"
> >  #include "../virt-dma.h"
> >
> > -#define PDMA_NR_CH                                   4
> > -
> > -#if (PDMA_NR_CH != 4)
> > -#error "Please define PDMA_NR_CH to 4"
> > -#endif
> > +#define PDMA_MAX_NR_CH                                       4
> >
> >  #define PDMA_BASE_ADDR                                       0x3000000
> >  #define PDMA_CHAN_OFFSET                             0x1000
> > @@ -118,7 +114,7 @@ struct sf_pdma {
> >       void __iomem            *membase;
> >       void __iomem            *mappedbase;
> >       u32                     n_chans;
> > -     struct sf_pdma_chan     chans[PDMA_NR_CH];
> > +     struct sf_pdma_chan     chans[PDMA_MAX_NR_CH];
> >  };
> >
> >  #endif /* _SF_PDMA_H */

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Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Geert Uytterhoeven]

Hi Zong, Palmer,

On Fri, Jan 21, 2022 at 3:21 AM Zong Li <zong.li@sifive.com> wrote:
> On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > > It currently assumes that there are always four channels, it would
> > > cause the error if there is actually less than four channels. Change
> > > that by getting number of channel from device tree.
> > >
> > > For backwards-compatible, it uses the default value (i.e. 4) when there
> > > is no 'dma-channels' information in dts.
> >
> > Some of the same wording issues here as those I pointed out in the DT
> > bindings patch.
> >
> > > Signed-off-by: Zong Li <zong.li@sifive.com>

> > > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> > >  static int sf_pdma_probe(struct platform_device *pdev)
> > >  {
> > >       struct sf_pdma *pdma;
> > > -     struct sf_pdma_chan *chan;
> > >       struct resource *res;
> > > -     int len, chans;
> > >       int ret;
> > >       const enum dma_slave_buswidth widths =
> > >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> > >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> > >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> > >
> > > -     chans = PDMA_NR_CH;
> > > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> > >       if (!pdma)
> > >               return -ENOMEM;
> > >
> > > -     pdma->n_chans = chans;
> > > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > > +                                &pdma->n_chans);
> > > +     if (ret) {
> > > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > > +     }
> > > +
> > > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > > +             return -EINVAL;
> >
> > Can we get away with just using only the number of channels the driver
> > actually supports?  ie, just never sending an op to the channels above
> > MAX_NR_CH?  That should leave us with nothing to track.

In theory we can...

> It might be a bit like when pdma->n_chans is bigger than the maximum,
> set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
> don't access the channels above the maximum. If I understand
> correctly, I gave the similar thought in the thread of v2 patch, and
> there are some discussions on that, but this way seems to lead to
> hard-to-track problems.

... but that would mean that when a new variant appears that supports
more channels, no error is printed, and people might not notice
immediately that the higher channels are never used.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Geert Uytterhoeven]

Hi Zong, Palmer,

On Fri, Jan 21, 2022 at 3:21 AM Zong Li <zong.li@sifive.com> wrote:
> On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > > It currently assumes that there are always four channels, it would
> > > cause the error if there is actually less than four channels. Change
> > > that by getting number of channel from device tree.
> > >
> > > For backwards-compatible, it uses the default value (i.e. 4) when there
> > > is no 'dma-channels' information in dts.
> >
> > Some of the same wording issues here as those I pointed out in the DT
> > bindings patch.
> >
> > > Signed-off-by: Zong Li <zong.li@sifive.com>

> > > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> > >  static int sf_pdma_probe(struct platform_device *pdev)
> > >  {
> > >       struct sf_pdma *pdma;
> > > -     struct sf_pdma_chan *chan;
> > >       struct resource *res;
> > > -     int len, chans;
> > >       int ret;
> > >       const enum dma_slave_buswidth widths =
> > >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> > >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> > >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> > >
> > > -     chans = PDMA_NR_CH;
> > > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> > >       if (!pdma)
> > >               return -ENOMEM;
> > >
> > > -     pdma->n_chans = chans;
> > > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > > +                                &pdma->n_chans);
> > > +     if (ret) {
> > > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > > +     }
> > > +
> > > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > > +             return -EINVAL;
> >
> > Can we get away with just using only the number of channels the driver
> > actually supports?  ie, just never sending an op to the channels above
> > MAX_NR_CH?  That should leave us with nothing to track.

In theory we can...

> It might be a bit like when pdma->n_chans is bigger than the maximum,
> set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
> don't access the channels above the maximum. If I understand
> correctly, I gave the similar thought in the thread of v2 patch, and
> there are some discussions on that, but this way seems to lead to
> hard-to-track problems.

... but that would mean that when a new variant appears that supports
more channels, no error is printed, and people might not notice
immediately that the higher channels are never used.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

On Fri, Jan 21, 2022 at 4:33 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Zong, Palmer,
>
> On Fri, Jan 21, 2022 at 3:21 AM Zong Li <zong.li@sifive.com> wrote:
> > On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > > On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > > > It currently assumes that there are always four channels, it would
> > > > cause the error if there is actually less than four channels. Change
> > > > that by getting number of channel from device tree.
> > > >
> > > > For backwards-compatible, it uses the default value (i.e. 4) when there
> > > > is no 'dma-channels' information in dts.
> > >
> > > Some of the same wording issues here as those I pointed out in the DT
> > > bindings patch.
> > >
> > > > Signed-off-by: Zong Li <zong.li@sifive.com>
>
> > > > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > > > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > > > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> > > >  static int sf_pdma_probe(struct platform_device *pdev)
> > > >  {
> > > >       struct sf_pdma *pdma;
> > > > -     struct sf_pdma_chan *chan;
> > > >       struct resource *res;
> > > > -     int len, chans;
> > > >       int ret;
> > > >       const enum dma_slave_buswidth widths =
> > > >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > > > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> > > >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> > > >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> > > >
> > > > -     chans = PDMA_NR_CH;
> > > > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > > > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > > > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> > > >       if (!pdma)
> > > >               return -ENOMEM;
> > > >
> > > > -     pdma->n_chans = chans;
> > > > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > > > +                                &pdma->n_chans);
> > > > +     if (ret) {
> > > > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > > > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > > > +     }
> > > > +
> > > > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > > > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > > > +             return -EINVAL;
> > >
> > > Can we get away with just using only the number of channels the driver
> > > actually supports?  ie, just never sending an op to the channels above
> > > MAX_NR_CH?  That should leave us with nothing to track.
>
> In theory we can...
>
> > It might be a bit like when pdma->n_chans is bigger than the maximum,
> > set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
> > don't access the channels above the maximum. If I understand
> > correctly, I gave the similar thought in the thread of v2 patch, and
> > there are some discussions on that, but this way seems to lead to
> > hard-to-track problems.
>
> ... but that would mean that when a new variant appears that supports
> more channels, no error is printed, and people might not notice
> immediately that the higher channels are never used.
>

I guess people might need to follow the dt-bindings, so they couldn't
specify the number of channels to the value which is more than
maximum. But as you mentioned, if people don't notice that and specify
it more than maximum,  they wouldn't be aware that the higher channels
are never used. It seems to me that we could keep returning the error
there, or show a warning message and use PDMA_MAX_NR_CH in that
situation, both looks good to me.

> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

On Fri, Jan 21, 2022 at 4:33 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Zong, Palmer,
>
> On Fri, Jan 21, 2022 at 3:21 AM Zong Li <zong.li@sifive.com> wrote:
> > On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > > On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > > > It currently assumes that there are always four channels, it would
> > > > cause the error if there is actually less than four channels. Change
> > > > that by getting number of channel from device tree.
> > > >
> > > > For backwards-compatible, it uses the default value (i.e. 4) when there
> > > > is no 'dma-channels' information in dts.
> > >
> > > Some of the same wording issues here as those I pointed out in the DT
> > > bindings patch.
> > >
> > > > Signed-off-by: Zong Li <zong.li@sifive.com>
>
> > > > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > > > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > > > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> > > >  static int sf_pdma_probe(struct platform_device *pdev)
> > > >  {
> > > >       struct sf_pdma *pdma;
> > > > -     struct sf_pdma_chan *chan;
> > > >       struct resource *res;
> > > > -     int len, chans;
> > > >       int ret;
> > > >       const enum dma_slave_buswidth widths =
> > > >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > > > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> > > >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> > > >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> > > >
> > > > -     chans = PDMA_NR_CH;
> > > > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > > > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > > > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> > > >       if (!pdma)
> > > >               return -ENOMEM;
> > > >
> > > > -     pdma->n_chans = chans;
> > > > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > > > +                                &pdma->n_chans);
> > > > +     if (ret) {
> > > > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > > > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > > > +     }
> > > > +
> > > > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > > > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > > > +             return -EINVAL;
> > >
> > > Can we get away with just using only the number of channels the driver
> > > actually supports?  ie, just never sending an op to the channels above
> > > MAX_NR_CH?  That should leave us with nothing to track.
>
> In theory we can...
>
> > It might be a bit like when pdma->n_chans is bigger than the maximum,
> > set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
> > don't access the channels above the maximum. If I understand
> > correctly, I gave the similar thought in the thread of v2 patch, and
> > there are some discussions on that, but this way seems to lead to
> > hard-to-track problems.
>
> ... but that would mean that when a new variant appears that supports
> more channels, no error is printed, and people might not notice
> immediately that the higher channels are never used.
>

I guess people might need to follow the dt-bindings, so they couldn't
specify the number of channels to the value which is more than
maximum. But as you mentioned, if people don't notice that and specify
it more than maximum,  they wouldn't be aware that the higher channels
are never used. It seems to me that we could keep returning the error
there, or show a warning message and use PDMA_MAX_NR_CH in that
situation, both looks good to me.

> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

_______________________________________________
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Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

On Fri, Jan 21, 2022 at 6:29 PM Zong Li <zong.li@sifive.com> wrote:
>
> On Fri, Jan 21, 2022 at 4:33 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >
> > Hi Zong, Palmer,
> >
> > On Fri, Jan 21, 2022 at 3:21 AM Zong Li <zong.li@sifive.com> wrote:
> > > On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > > > On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > > > > It currently assumes that there are always four channels, it would
> > > > > cause the error if there is actually less than four channels. Change
> > > > > that by getting number of channel from device tree.
> > > > >
> > > > > For backwards-compatible, it uses the default value (i.e. 4) when there
> > > > > is no 'dma-channels' information in dts.
> > > >
> > > > Some of the same wording issues here as those I pointed out in the DT
> > > > bindings patch.
> > > >
> > > > > Signed-off-by: Zong Li <zong.li@sifive.com>
> >
> > > > > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > > > > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > > > > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> > > > >  static int sf_pdma_probe(struct platform_device *pdev)
> > > > >  {
> > > > >       struct sf_pdma *pdma;
> > > > > -     struct sf_pdma_chan *chan;
> > > > >       struct resource *res;
> > > > > -     int len, chans;
> > > > >       int ret;
> > > > >       const enum dma_slave_buswidth widths =
> > > > >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > > > > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> > > > >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> > > > >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> > > > >
> > > > > -     chans = PDMA_NR_CH;
> > > > > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > > > > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > > > > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> > > > >       if (!pdma)
> > > > >               return -ENOMEM;
> > > > >
> > > > > -     pdma->n_chans = chans;
> > > > > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > > > > +                                &pdma->n_chans);
> > > > > +     if (ret) {
> > > > > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > > > > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > > > > +     }
> > > > > +
> > > > > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > > > > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > > > > +             return -EINVAL;
> > > >
> > > > Can we get away with just using only the number of channels the driver
> > > > actually supports?  ie, just never sending an op to the channels above
> > > > MAX_NR_CH?  That should leave us with nothing to track.
> >
> > In theory we can...
> >
> > > It might be a bit like when pdma->n_chans is bigger than the maximum,
> > > set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
> > > don't access the channels above the maximum. If I understand
> > > correctly, I gave the similar thought in the thread of v2 patch, and
> > > there are some discussions on that, but this way seems to lead to
> > > hard-to-track problems.
> >
> > ... but that would mean that when a new variant appears that supports
> > more channels, no error is printed, and people might not notice
> > immediately that the higher channels are never used.
> >
>
> I guess people might need to follow the dt-bindings, so they couldn't
> specify the number of channels to the value which is more than
> maximum. But as you mentioned, if people don't notice that and specify
> it more than maximum,  they wouldn't be aware that the higher channels
> are never used. It seems to me that we could keep returning the error
> there, or show a warning message and use PDMA_MAX_NR_CH in that
> situation, both looks good to me.
>

Hi all, thank you for the review, I'd like to prepare the next version
patch, if current implementation of this part is ok to you, I will
keep it in the next version. Please let me know if anything can be
improved. Thanks

> > Gr{oetje,eeting}s,
> >
> >                         Geert
> >
> > --
> > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> >
> > In personal conversations with technical people, I call myself a hacker. But
> > when I'm talking to journalists I just say "programmer" or something like that.
> >                                 -- Linus Torvalds

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Re: [PATCH v4 3/3] dmaengine: sf-pdma: Get number of channel by device tree

[Zong Li]

On Fri, Jan 21, 2022 at 6:29 PM Zong Li <zong.li@sifive.com> wrote:
>
> On Fri, Jan 21, 2022 at 4:33 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >
> > Hi Zong, Palmer,
> >
> > On Fri, Jan 21, 2022 at 3:21 AM Zong Li <zong.li@sifive.com> wrote:
> > > On Fri, Jan 21, 2022 at 2:52 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > > > On Sun, 16 Jan 2022 17:35:28 PST (-0800), zong.li@sifive.com wrote:
> > > > > It currently assumes that there are always four channels, it would
> > > > > cause the error if there is actually less than four channels. Change
> > > > > that by getting number of channel from device tree.
> > > > >
> > > > > For backwards-compatible, it uses the default value (i.e. 4) when there
> > > > > is no 'dma-channels' information in dts.
> > > >
> > > > Some of the same wording issues here as those I pointed out in the DT
> > > > bindings patch.
> > > >
> > > > > Signed-off-by: Zong Li <zong.li@sifive.com>
> >
> > > > > --- a/drivers/dma/sf-pdma/sf-pdma.c
> > > > > +++ b/drivers/dma/sf-pdma/sf-pdma.c
> > > > > @@ -482,9 +482,7 @@ static void sf_pdma_setup_chans(struct sf_pdma *pdma)
> > > > >  static int sf_pdma_probe(struct platform_device *pdev)
> > > > >  {
> > > > >       struct sf_pdma *pdma;
> > > > > -     struct sf_pdma_chan *chan;
> > > > >       struct resource *res;
> > > > > -     int len, chans;
> > > > >       int ret;
> > > > >       const enum dma_slave_buswidth widths =
> > > > >               DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
> > > > > @@ -492,13 +490,21 @@ static int sf_pdma_probe(struct platform_device *pdev)
> > > > >               DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES |
> > > > >               DMA_SLAVE_BUSWIDTH_64_BYTES;
> > > > >
> > > > > -     chans = PDMA_NR_CH;
> > > > > -     len = sizeof(*pdma) + sizeof(*chan) * chans;
> > > > > -     pdma = devm_kzalloc(&pdev->dev, len, GFP_KERNEL);
> > > > > +     pdma = devm_kzalloc(&pdev->dev, sizeof(*pdma), GFP_KERNEL);
> > > > >       if (!pdma)
> > > > >               return -ENOMEM;
> > > > >
> > > > > -     pdma->n_chans = chans;
> > > > > +     ret = of_property_read_u32(pdev->dev.of_node, "dma-channels",
> > > > > +                                &pdma->n_chans);
> > > > > +     if (ret) {
> > > > > +             dev_notice(&pdev->dev, "set number of channels to default value: 4\n");
> > > > > +             pdma->n_chans = PDMA_MAX_NR_CH;
> > > > > +     }
> > > > > +
> > > > > +     if (pdma->n_chans > PDMA_MAX_NR_CH) {
> > > > > +             dev_err(&pdev->dev, "the number of channels exceeds the maximum\n");
> > > > > +             return -EINVAL;
> > > >
> > > > Can we get away with just using only the number of channels the driver
> > > > actually supports?  ie, just never sending an op to the channels above
> > > > MAX_NR_CH?  That should leave us with nothing to track.
> >
> > In theory we can...
> >
> > > It might be a bit like when pdma->n_chans is bigger than the maximum,
> > > set the pdma->chans to PDMA_MAX_NR_CH, then we could ensure that we
> > > don't access the channels above the maximum. If I understand
> > > correctly, I gave the similar thought in the thread of v2 patch, and
> > > there are some discussions on that, but this way seems to lead to
> > > hard-to-track problems.
> >
> > ... but that would mean that when a new variant appears that supports
> > more channels, no error is printed, and people might not notice
> > immediately that the higher channels are never used.
> >
>
> I guess people might need to follow the dt-bindings, so they couldn't
> specify the number of channels to the value which is more than
> maximum. But as you mentioned, if people don't notice that and specify
> it more than maximum,  they wouldn't be aware that the higher channels
> are never used. It seems to me that we could keep returning the error
> there, or show a warning message and use PDMA_MAX_NR_CH in that
> situation, both looks good to me.
>

Hi all, thank you for the review, I'd like to prepare the next version
patch, if current implementation of this part is ok to you, I will
keep it in the next version. Please let me know if anything can be
improved. Thanks

> > Gr{oetje,eeting}s,
> >
> >                         Geert
> >
> > --
> > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> >
> > In personal conversations with technical people, I call myself a hacker. But
> > when I'm talking to journalists I just say "programmer" or something like that.
> >                                 -- Linus Torvalds

Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Vinod Koul]

On 17-01-22, 09:35, Zong Li wrote:
> Add dma-channels property, then we can determine how many channels there
> by device tree.
> 
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
>  arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> index c9f6d205d2ba..3c48f2d7a4a4 100644
> --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> @@ -188,6 +188,7 @@ dma@3000000 {

Unrelated but the node name should be dma-controller@...

>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>  
> diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> index 0655b5c4201d..2bdfe7f06e4b 100644
> --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> @@ -171,6 +171,7 @@ dma: dma@3000000 {
>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic0>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>  		uart1: serial@10011000 {
> -- 
> 2.31.1

-- 
~Vinod

Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Vinod Koul]

On 17-01-22, 09:35, Zong Li wrote:
> Add dma-channels property, then we can determine how many channels there
> by device tree.
> 
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
>  arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> index c9f6d205d2ba..3c48f2d7a4a4 100644
> --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> @@ -188,6 +188,7 @@ dma@3000000 {

Unrelated but the node name should be dma-controller@...

>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>  
> diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> index 0655b5c4201d..2bdfe7f06e4b 100644
> --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> @@ -171,6 +171,7 @@ dma: dma@3000000 {
>  			reg = <0x0 0x3000000 0x0 0x8000>;
>  			interrupt-parent = <&plic0>;
>  			interrupts = <23 24 25 26 27 28 29 30>;
> +			dma-channels = <4>;
>  			#dma-cells = <1>;
>  		};
>  		uart1: serial@10011000 {
> -- 
> 2.31.1

-- 
~Vinod

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Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Zong Li]

On Thu, Jan 27, 2022 at 3:03 PM Vinod Koul <vkoul@kernel.org> wrote:
>
> On 17-01-22, 09:35, Zong Li wrote:
> > Add dma-channels property, then we can determine how many channels there
> > by device tree.
> >
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > ---
> >  arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
> >  arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
> >  2 files changed, 2 insertions(+)
> >
> > diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> > index c9f6d205d2ba..3c48f2d7a4a4 100644
> > --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> > +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> > @@ -188,6 +188,7 @@ dma@3000000 {
>
> Unrelated but the node name should be dma-controller@...
>

Thanks for the correction, I guess we could give another patch for
changing the node name.

> >                       reg = <0x0 0x3000000 0x0 0x8000>;
> >                       interrupt-parent = <&plic>;
> >                       interrupts = <23 24 25 26 27 28 29 30>;
> > +                     dma-channels = <4>;
> >                       #dma-cells = <1>;
> >               };
> >
> > diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> > index 0655b5c4201d..2bdfe7f06e4b 100644
> > --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> > +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> > @@ -171,6 +171,7 @@ dma: dma@3000000 {
> >                       reg = <0x0 0x3000000 0x0 0x8000>;
> >                       interrupt-parent = <&plic0>;
> >                       interrupts = <23 24 25 26 27 28 29 30>;
> > +                     dma-channels = <4>;
> >                       #dma-cells = <1>;
> >               };
> >               uart1: serial@10011000 {
> > --
> > 2.31.1
>
> --
> ~Vinod

Re: [PATCH v4 1/3] riscv: dts: Add dma-channels property in dma node

[Zong Li]

On Thu, Jan 27, 2022 at 3:03 PM Vinod Koul <vkoul@kernel.org> wrote:
>
> On 17-01-22, 09:35, Zong Li wrote:
> > Add dma-channels property, then we can determine how many channels there
> > by device tree.
> >
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > ---
> >  arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi | 1 +
> >  arch/riscv/boot/dts/sifive/fu540-c000.dtsi        | 1 +
> >  2 files changed, 2 insertions(+)
> >
> > diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> > index c9f6d205d2ba..3c48f2d7a4a4 100644
> > --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> > +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> > @@ -188,6 +188,7 @@ dma@3000000 {
>
> Unrelated but the node name should be dma-controller@...
>

Thanks for the correction, I guess we could give another patch for
changing the node name.

> >                       reg = <0x0 0x3000000 0x0 0x8000>;
> >                       interrupt-parent = <&plic>;
> >                       interrupts = <23 24 25 26 27 28 29 30>;
> > +                     dma-channels = <4>;
> >                       #dma-cells = <1>;
> >               };
> >
> > diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> > index 0655b5c4201d..2bdfe7f06e4b 100644
> > --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> > +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> > @@ -171,6 +171,7 @@ dma: dma@3000000 {
> >                       reg = <0x0 0x3000000 0x0 0x8000>;
> >                       interrupt-parent = <&plic0>;
> >                       interrupts = <23 24 25 26 27 28 29 30>;
> > +                     dma-channels = <4>;
> >                       #dma-cells = <1>;
> >               };
> >               uart1: serial@10011000 {
> > --
> > 2.31.1
>
> --
> ~Vinod

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