[PATCH v8 0/2] Enable multiple MCAN on AM62x

[PATCH v8 0/2] Enable multiple MCAN on AM62x

[Judith Mendez]

On AM62x there are two MCANs in MCU domain. The MCANs in MCU domain
were not enabled since there is no hardware interrupt routed to A53
GIC interrupt controller. Therefore A53 Linux cannot be interrupted
by MCU MCANs.

This solution instantiates a hrtimer with 1 ms polling interval
for MCAN device when there is no hardware interrupt property in
DTB MCAN node. The hrtimer generates a recurring software interrupt
which allows to call the isr. The isr will check if there is pending
transaction by reading a register and proceed normally if there is.
MCANs with hardware interrupt routed to A53 Linux will continue to
use the hardware interrupt as expected.

Timer polling method was tested on both classic CAN and CAN-FD
at 125 KBPS, 250 KBPS, 1 MBPS and 2.5 MBPS with 4 MBPS bitrate
switching.

Letency and CPU load benchmarks were tested on 3x MCAN on AM62x.
1 MBPS timer polling interval is the better timer polling interval
since it has comparable latency to hardware interrupt with the worse
case being 1ms + CAN frame propagation time and CPU load is not
substantial. Latency can be improved further with less than 1 ms
polling intervals, howerver it is at the cost of CPU usage since CPU
load increases at 0.5 ms.

Note that in terms of power, enabling MCU MCANs with timer-polling
implementation might have negative impact since we will have to wake
up every 1 ms whether there are CAN packets pending in the RX FIFO or
not. This might prevent the CPU from entering into deeper idle states
for extended periods of time.

v7:
Link: https://lore.kernel.org/linux-can/20230523023749.4526-1-jm@ti.com/T/#t

v6:
Link: https://lore.kernel.org/linux-can/20230518193613.15185-1-jm@ti.com/T/#t

v5:
Link: https://lore.kernel.org/linux-can/20230510202952.27111-1-jm@ti.com/T/#t

v4:
Link: https://lore.kernel.org/linux-can/c3395692-7dbf-19b2-bd3f-31ba86fa4ac9@linaro.org/T/#t

v2:
Link: https://lore.kernel.org/linux-can/20230424195402.516-1-jm@ti.com/T/#t

V1:
Link: https://lore.kernel.org/linux-can/19d8ae7f-7b74-a869-a818-93b74d106709@ti.com/T/#t

RFC:
Link: https://lore.kernel.org/linux-can/52a37e51-4143-9017-42ee-8d17c67028e3@ti.com/T/#t

v7:
- Cancel hrtimer after interrupts in m_can_stop
- Move assignment of hrtimer_callback to m_can_class_register()
- Initialize irq = 0 if polling mode is used

v6:
- Clean up m_can_platform.c after removing poll-interval

v6:
- Move hrtimer stop/start function calls to m_can_open and m_can_close to
support power suspend/resume

v5:
- Remove poll-interval in bindings
- Change dev_dbg to dev_info if hardware int exists and polling
is enabled

v4:
- Wrong patches sent

v3:
- Update binding poll-interval description
- Add oneOf to select either interrupts/798d276b39e984345d52b933a900a71fa0815928
v2:
- Add poll-interval property to bindings and MCAN DTB node
- Add functionality to check for 'poll-interval' property in MCAN node 
- Bindings: add an example using poll-interval
- Add 'polling' flag in driver to check if device is using polling method
- Check for timer polling and hardware interrupt cases, default to
hardware interrupt method
- Change ns_to_ktime() to ms_to_ktime()

Judith Mendez (2):
  dt-bindings: net: can: Remove interrupt properties for MCAN
  can: m_can: Add hrtimer to generate software interrupt

 .../bindings/net/can/bosch,m_can.yaml         | 20 +++++++++--
 drivers/net/can/m_can/m_can.c                 | 34 +++++++++++++++++--
 drivers/net/can/m_can/m_can.h                 |  3 ++
 drivers/net/can/m_can/m_can_platform.c        | 24 +++++++++++--
 4 files changed, 74 insertions(+), 7 deletions(-)


base-commit: 798d276b39e984345d52b933a900a71fa0815928
-- 
2.34.1

[PATCH v8 1/2] dt-bindings: net: can: Remove interrupt properties for MCAN

[Judith Mendez]

On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
routed to A53 Linux, instead they will use software interrupt by
timer polling.

To enable timer polling method, interrupts should be
optional so remove interrupts property from required section and
add an example for MCAN node with timer polling enabled.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Judith Mendez <jm@ti.com>
---
Changelog:
v8:
   1. No changes
v7:
   1. No changes
v6:
   1. No changes
v5:
   1. Remove poll-interval
   2. Remove oneOf that selects interrupts/interrupt-names or poll-interval
v3:
   1. Update binding poll-interval description
   2. Add oneOf to select interrupts/interrupt-names or poll-interval
v2:
   1. Add poll-interval property to enable timer polling method
   2. Add example using poll-interval property
---
 .../bindings/net/can/bosch,m_can.yaml         | 20 +++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml b/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml
index 67879aab623b..bb518c831f7b 100644
--- a/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml
+++ b/Documentation/devicetree/bindings/net/can/bosch,m_can.yaml
@@ -122,8 +122,6 @@ required:
   - compatible
   - reg
   - reg-names
-  - interrupts
-  - interrupt-names
   - clocks
   - clock-names
   - bosch,mram-cfg
@@ -132,6 +130,7 @@ additionalProperties: false
 
 examples:
   - |
+    // Example with interrupts
     #include <dt-bindings/clock/imx6sx-clock.h>
     can@20e8000 {
       compatible = "bosch,m_can";
@@ -149,4 +148,21 @@ examples:
       };
     };
 
+  - |
+    // Example with timer polling
+    #include <dt-bindings/clock/imx6sx-clock.h>
+    can@20e8000 {
+      compatible = "bosch,m_can";
+      reg = <0x020e8000 0x4000>, <0x02298000 0x4000>;
+      reg-names = "m_can", "message_ram";
+      clocks = <&clks IMX6SX_CLK_CANFD>,
+               <&clks IMX6SX_CLK_CANFD>;
+      clock-names = "hclk", "cclk";
+      bosch,mram-cfg = <0x0 0 0 32 0 0 0 1>;
+
+      can-transceiver {
+        max-bitrate = <5000000>;
+      };
+    };
+
 ...
-- 
2.34.1

Re: [PATCH v8 1/2] dt-bindings: net: can: Remove interrupt properties for MCAN

[Tony Lindgren]

* Judith Mendez <jm@ti.com> [230530 22:48]:
> On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
> routed to A53 Linux, instead they will use software interrupt by
> timer polling.
> 
> To enable timer polling method, interrupts should be
> optional so remove interrupts property from required section and
> add an example for MCAN node with timer polling enabled.

Reviewed-by: Tony Lindgren <tony@atomide.com>

[PATCH v8 2/2] can: m_can: Add hrtimer to generate software interrupt

[Judith Mendez]

Introduce timer polling method to MCAN since some SoCs may not
have M_CAN interrupt routed to A53 Linux and do not have
interrupt property in device tree M_CAN node.

On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
routed to A53 Linux, instead they will use timer polling method.

Add an hrtimer to MCAN class device. Each MCAN will have its own
hrtimer instantiated if there is no hardware interrupt found in
device tree M_CAN node. The timer will generate a software
interrupt every 1 ms. In hrtimer callback, we check if there is
a transaction pending by reading a register, then process by
calling the isr if there is.

Signed-off-by: Judith Mendez <jm@ti.com>
---
Changelog:
v8:
- Cancel hrtimer after interrupts in m_can_stop
- Move assignment of hrtimer_callback to m_can_class_register()
- Initialize irq = 0 if polling mode is used
- Add reson for polling mode in commit msg
- Remove unrelated change
- Remove polling flag
v7:
- Clean up m_can_platform.c if/else section after removing poll-interval
- Remove poll-interval from patch description
v6:
- Move hrtimer stop/start function calls to m_can_open and m_can_close to
support power suspend/resume
v5:
- Change dev_dbg to dev_info if hardware interrupt exists and polling
is enabled
v4:
- No changes
v3:
- Create a define for 1 ms polling interval
- Change plarform_get_irq to optional to not print error msg
v2:
- Add functionality to check for 'poll-interval' property in MCAN node 
- Add 'polling' flag in driver to check if device is using polling method
- Check for timer polling and hardware interrupt cases, default to
hardware interrupt method
- Change ns_to_ktime() to ms_to_ktime()
---
 drivers/net/can/m_can/m_can.c          | 34 ++++++++++++++++++++++++--
 drivers/net/can/m_can/m_can.h          |  3 +++
 drivers/net/can/m_can/m_can_platform.c | 24 +++++++++++++++---
 3 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index a5003435802b..d1d1de94e590 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -11,6 +11,7 @@
 #include <linux/bitfield.h>
 #include <linux/can/dev.h>
 #include <linux/ethtool.h>
+#include <linux/hrtimer.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
@@ -308,6 +309,9 @@ enum m_can_reg {
 #define TX_EVENT_MM_MASK	GENMASK(31, 24)
 #define TX_EVENT_TXTS_MASK	GENMASK(15, 0)
 
+/* Hrtimer polling interval */
+#define HRTIMER_POLL_INTERVAL		1
+
 /* The ID and DLC registers are adjacent in M_CAN FIFO memory,
  * and we can save a (potentially slow) bus round trip by combining
  * reads and writes to them.
@@ -1414,6 +1418,12 @@ static int m_can_start(struct net_device *dev)
 
 	m_can_enable_all_interrupts(cdev);
 
+	if (dev->irq == 0) {
+		dev_dbg(cdev->dev, "Start hrtimer\n");
+		hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
+			      HRTIMER_MODE_REL_PINNED);
+	}
+
 	return 0;
 }
 
@@ -1568,6 +1578,11 @@ static void m_can_stop(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
 
+	if (dev->irq == 0) {
+		dev_dbg(cdev->dev, "Stop hrtimer\n");
+		hrtimer_cancel(&cdev->hrtimer);
+	}
+
 	/* disable all interrupts */
 	m_can_disable_all_interrupts(cdev);
 
@@ -1793,6 +1808,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 }
 
+static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
+{
+	struct m_can_classdev *cdev = container_of(timer, struct
+						   m_can_classdev, hrtimer);
+
+	m_can_isr(0, cdev->net);
+
+	hrtimer_forward_now(timer, ms_to_ktime(HRTIMER_POLL_INTERVAL));
+
+	return HRTIMER_RESTART;
+}
+
 static int m_can_open(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
@@ -1831,10 +1858,10 @@ static int m_can_open(struct net_device *dev)
 		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
 					   IRQF_ONESHOT,
 					   dev->name, dev);
-	} else {
+	}
+	if (dev->irq > 0)
 		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
 				  dev);
-	}
 
 	if (err < 0) {
 		netdev_err(dev, "failed to request interrupt\n");
@@ -2027,6 +2054,9 @@ int m_can_class_register(struct m_can_classdev *cdev)
 			goto clk_disable;
 	}
 
+	if (cdev->net->irq == 0)
+		cdev->hrtimer.function = &hrtimer_callback;
+
 	ret = m_can_dev_setup(cdev);
 	if (ret)
 		goto rx_offload_del;
diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
index a839dc71dc9b..2ac18ac867a4 100644
--- a/drivers/net/can/m_can/m_can.h
+++ b/drivers/net/can/m_can/m_can.h
@@ -15,6 +15,7 @@
 #include <linux/device.h>
 #include <linux/dma-mapping.h>
 #include <linux/freezer.h>
+#include <linux/hrtimer.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
@@ -93,6 +94,8 @@ struct m_can_classdev {
 	int is_peripheral;
 
 	struct mram_cfg mcfg[MRAM_CFG_NUM];
+
+	struct hrtimer hrtimer;
 };
 
 struct m_can_classdev *m_can_class_allocate_dev(struct device *dev, int sizeof_priv);
diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
index 94dc82644113..a7ab2c8b55d1 100644
--- a/drivers/net/can/m_can/m_can_platform.c
+++ b/drivers/net/can/m_can/m_can_platform.c
@@ -5,6 +5,7 @@
 //
 // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
 
+#include <linux/hrtimer.h>
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
 
@@ -96,12 +97,29 @@ static int m_can_plat_probe(struct platform_device *pdev)
 		goto probe_fail;
 
 	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
-	irq = platform_get_irq_byname(pdev, "int0");
-	if (IS_ERR(addr) || irq < 0) {
-		ret = -EINVAL;
+	if (IS_ERR(addr)) {
+		ret = PTR_ERR(addr);
 		goto probe_fail;
 	}
 
+	if (device_property_present(mcan_class->dev, "interrupts") ||
+	    device_property_present(mcan_class->dev, "interrupt-names")) {
+		irq = platform_get_irq_byname(pdev, "int0");
+		if (irq == -EPROBE_DEFER) {
+			ret = -EPROBE_DEFER;
+			goto probe_fail;
+		}
+		if (irq < 0) {
+			ret = -EINVAL;
+			goto probe_fail;
+		}
+	} else {
+		irq = 0;
+		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
+		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
+			     HRTIMER_MODE_REL_PINNED);
+	}
+
 	/* message ram could be shared */
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
 	if (!res) {
-- 
2.34.1

Re: [PATCH v8 2/2] can: m_can: Add hrtimer to generate software interrupt

[Tony Lindgren]

* Judith Mendez <jm@ti.com> [230530 22:48]:
> Introduce timer polling method to MCAN since some SoCs may not
> have M_CAN interrupt routed to A53 Linux and do not have
> interrupt property in device tree M_CAN node.
> 
> On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
> routed to A53 Linux, instead they will use timer polling method.
> 
> Add an hrtimer to MCAN class device. Each MCAN will have its own
> hrtimer instantiated if there is no hardware interrupt found in
> device tree M_CAN node. The timer will generate a software
> interrupt every 1 ms. In hrtimer callback, we check if there is
> a transaction pending by reading a register, then process by
> calling the isr if there is.

Reviewed-by: Tony Lindgren <tony@atomide.com>

Re: [PATCH v8 2/2] can: m_can: Add hrtimer to generate software interrupt

[Marc Kleine-Budde]

[-- Attachment #1: Type: text/plain, Size: 7724 bytes --]

On 30.05.2023 17:48:20, Judith Mendez wrote:
> Introduce timer polling method to MCAN since some SoCs may not
> have M_CAN interrupt routed to A53 Linux and do not have
> interrupt property in device tree M_CAN node.
> 
> On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
> routed to A53 Linux, instead they will use timer polling method.
> 
> Add an hrtimer to MCAN class device. Each MCAN will have its own
> hrtimer instantiated if there is no hardware interrupt found in
> device tree M_CAN node. The timer will generate a software
> interrupt every 1 ms. In hrtimer callback, we check if there is
> a transaction pending by reading a register, then process by
> calling the isr if there is.
> 
> Signed-off-by: Judith Mendez <jm@ti.com>
> ---
> Changelog:
> v8:
> - Cancel hrtimer after interrupts in m_can_stop
> - Move assignment of hrtimer_callback to m_can_class_register()
> - Initialize irq = 0 if polling mode is used
> - Add reson for polling mode in commit msg
> - Remove unrelated change
> - Remove polling flag
> v7:
> - Clean up m_can_platform.c if/else section after removing poll-interval
> - Remove poll-interval from patch description
> v6:
> - Move hrtimer stop/start function calls to m_can_open and m_can_close to
> support power suspend/resume
> v5:
> - Change dev_dbg to dev_info if hardware interrupt exists and polling
> is enabled
> v4:
> - No changes
> v3:
> - Create a define for 1 ms polling interval
> - Change plarform_get_irq to optional to not print error msg
> v2:
> - Add functionality to check for 'poll-interval' property in MCAN node 
> - Add 'polling' flag in driver to check if device is using polling method
> - Check for timer polling and hardware interrupt cases, default to
> hardware interrupt method
> - Change ns_to_ktime() to ms_to_ktime()
> ---
>  drivers/net/can/m_can/m_can.c          | 34 ++++++++++++++++++++++++--
>  drivers/net/can/m_can/m_can.h          |  3 +++
>  drivers/net/can/m_can/m_can_platform.c | 24 +++++++++++++++---
>  3 files changed, 56 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index a5003435802b..d1d1de94e590 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -11,6 +11,7 @@
>  #include <linux/bitfield.h>
>  #include <linux/can/dev.h>
>  #include <linux/ethtool.h>
> +#include <linux/hrtimer.h>
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/iopoll.h>
> @@ -308,6 +309,9 @@ enum m_can_reg {
>  #define TX_EVENT_MM_MASK	GENMASK(31, 24)
>  #define TX_EVENT_TXTS_MASK	GENMASK(15, 0)
>  
> +/* Hrtimer polling interval */
> +#define HRTIMER_POLL_INTERVAL		1

Please add _MS to the macro name.

> +
>  /* The ID and DLC registers are adjacent in M_CAN FIFO memory,
>   * and we can save a (potentially slow) bus round trip by combining
>   * reads and writes to them.
> @@ -1414,6 +1418,12 @@ static int m_can_start(struct net_device *dev)
>  
>  	m_can_enable_all_interrupts(cdev);
>  
> +	if (dev->irq == 0) {

        if (!dev->irq) {

> +		dev_dbg(cdev->dev, "Start hrtimer\n");
> +		hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
> +			      HRTIMER_MODE_REL_PINNED);
> +	}
> +
>  	return 0;
>  }
>  
> @@ -1568,6 +1578,11 @@ static void m_can_stop(struct net_device *dev)
>  {
>  	struct m_can_classdev *cdev = netdev_priv(dev);
>  
> +	if (dev->irq == 0) {

        if (!dev->irq) {

> +		dev_dbg(cdev->dev, "Stop hrtimer\n");
> +		hrtimer_cancel(&cdev->hrtimer);
> +	}
> +
>  	/* disable all interrupts */
>  	m_can_disable_all_interrupts(cdev);
>  
> @@ -1793,6 +1808,18 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
>  	return NETDEV_TX_OK;
>  }
>  
> +static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
> +{
> +	struct m_can_classdev *cdev = container_of(timer, struct
> +						   m_can_classdev, hrtimer);
> +
> +	m_can_isr(0, cdev->net);
> +
> +	hrtimer_forward_now(timer, ms_to_ktime(HRTIMER_POLL_INTERVAL));
> +
> +	return HRTIMER_RESTART;
> +}
> +
>  static int m_can_open(struct net_device *dev)
>  {
>  	struct m_can_classdev *cdev = netdev_priv(dev);
> @@ -1831,10 +1858,10 @@ static int m_can_open(struct net_device *dev)
>  		err = request_threaded_irq(dev->irq, NULL, m_can_isr,
>  					   IRQF_ONESHOT,
>  					   dev->name, dev);
> -	} else {
> +	}
> +	if (dev->irq > 0)

I think you broke the peripheral case. Should be:

        } else if (dev->irq) {
                ...
        }

>  		err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
>  				  dev);
> -	}
>  
>  	if (err < 0) {
>  		netdev_err(dev, "failed to request interrupt\n");
> @@ -2027,6 +2054,9 @@ int m_can_class_register(struct m_can_classdev *cdev)
>  			goto clk_disable;
>  	}
>  
> +	if (cdev->net->irq == 0)

        if (!cdev->net->irq)

> +		cdev->hrtimer.function = &hrtimer_callback;
> +
>  	ret = m_can_dev_setup(cdev);
>  	if (ret)
>  		goto rx_offload_del;
> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
> index a839dc71dc9b..2ac18ac867a4 100644
> --- a/drivers/net/can/m_can/m_can.h
> +++ b/drivers/net/can/m_can/m_can.h
> @@ -15,6 +15,7 @@
>  #include <linux/device.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/freezer.h>
> +#include <linux/hrtimer.h>
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/iopoll.h>
> @@ -93,6 +94,8 @@ struct m_can_classdev {
>  	int is_peripheral;
>  
>  	struct mram_cfg mcfg[MRAM_CFG_NUM];
> +
> +	struct hrtimer hrtimer;
>  };
>  
>  struct m_can_classdev *m_can_class_allocate_dev(struct device *dev, int sizeof_priv);
> diff --git a/drivers/net/can/m_can/m_can_platform.c b/drivers/net/can/m_can/m_can_platform.c
> index 94dc82644113..a7ab2c8b55d1 100644
> --- a/drivers/net/can/m_can/m_can_platform.c
> +++ b/drivers/net/can/m_can/m_can_platform.c
> @@ -5,6 +5,7 @@
>  //
>  // Copyright (C) 2018-19 Texas Instruments Incorporated - http://www.ti.com/
>  
> +#include <linux/hrtimer.h>
>  #include <linux/phy/phy.h>
>  #include <linux/platform_device.h>
>  
> @@ -96,12 +97,29 @@ static int m_can_plat_probe(struct platform_device *pdev)
>  		goto probe_fail;
>  
>  	addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
> -	irq = platform_get_irq_byname(pdev, "int0");
> -	if (IS_ERR(addr) || irq < 0) {
> -		ret = -EINVAL;
> +	if (IS_ERR(addr)) {
> +		ret = PTR_ERR(addr);
>  		goto probe_fail;
>  	}
>  
> +	if (device_property_present(mcan_class->dev, "interrupts") ||
> +	    device_property_present(mcan_class->dev, "interrupt-names")) {
> +		irq = platform_get_irq_byname(pdev, "int0");
> +		if (irq == -EPROBE_DEFER) {
> +			ret = -EPROBE_DEFER;
> +			goto probe_fail;
> +		}
> +		if (irq < 0) {
> +			ret = -EINVAL;

please return the original error value.

> +			goto probe_fail;
> +		}
> +	} else {
> +		irq = 0;

Please initialize irq as 0 during declaration.

> +		dev_dbg(mcan_class->dev, "Polling enabled, initialize hrtimer");
> +		hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC,
> +			     HRTIMER_MODE_REL_PINNED);
> +	}
> +
>  	/* message ram could be shared */
>  	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
>  	if (!res) {
> -- 
> 2.34.1
> 
> 

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

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Re: [PATCH v8 2/2] can: m_can: Add hrtimer to generate software interrupt

[Hiago Franco]

On Wed, May 31, 2023 at 12:51 AM Judith Mendez <jm@ti.com> wrote:
>
> Introduce timer polling method to MCAN since some SoCs may not
> have M_CAN interrupt routed to A53 Linux and do not have
> interrupt property in device tree M_CAN node.
>
> On AM62x SoC, MCANs on MCU domain do not have hardware interrupt
> routed to A53 Linux, instead they will use timer polling method.
>
> Add an hrtimer to MCAN class device. Each MCAN will have its own
> hrtimer instantiated if there is no hardware interrupt found in
> device tree M_CAN node. The timer will generate a software
> interrupt every 1 ms. In hrtimer callback, we check if there is
> a transaction pending by reading a register, then process by
> calling the isr if there is.
>
> Signed-off-by: Judith Mendez <jm@ti.com>

Tested-by: Hiago De Franco <hiago.franco@toradex.com> # Toradex Verdin AM62

Re: [PATCH v8 0/2] Enable multiple MCAN on AM62x

[Judith Mendez]

Hi all,

On 5/30/23 5:48 PM, Judith Mendez wrote:
> On AM62x there are two MCANs in MCU domain. The MCANs in MCU domain
> were not enabled since there is no hardware interrupt routed to A53
> GIC interrupt controller. Therefore A53 Linux cannot be interrupted
> by MCU MCANs.
> 
> This solution instantiates a hrtimer with 1 ms polling interval
> for MCAN device when there is no hardware interrupt property in
> DTB MCAN node. The hrtimer generates a recurring software interrupt
> which allows to call the isr. The isr will check if there is pending
> transaction by reading a register and proceed normally if there is.
> MCANs with hardware interrupt routed to A53 Linux will continue to
> use the hardware interrupt as expected.
> 
> Timer polling method was tested on both classic CAN and CAN-FD
> at 125 KBPS, 250 KBPS, 1 MBPS and 2.5 MBPS with 4 MBPS bitrate
> switching.
> 
> Letency and CPU load benchmarks were tested on 3x MCAN on AM62x.
> 1 MBPS timer polling interval is the better timer polling interval
> since it has comparable latency to hardware interrupt with the worse
> case being 1ms + CAN frame propagation time and CPU load is not
> substantial. Latency can be improved further with less than 1 ms
> polling intervals, howerver it is at the cost of CPU usage since CPU
> load increases at 0.5 ms.
> 
> Note that in terms of power, enabling MCU MCANs with timer-polling
> implementation might have negative impact since we will have to wake
> up every 1 ms whether there are CAN packets pending in the RX FIFO or
> not. This might prevent the CPU from entering into deeper idle states
> for extended periods of time.

Was wondering if I am still pending some updates for this patch series? 
Or if any other issues please let me know. (: Thanks all

~ Judith