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Date: Sun, 16 Apr 2023 14:33:11 +0200
From: Oliver Hartkopp <socketcan@...tkopp.net>
To: Marc Kleine-Budde <mkl@...gutronix.de>, Judith Mendez <jm@...com>
Cc: Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
Nishanth Menon <nm@...com>,
Vignesh Raghavendra <vigneshr@...com>,
Andrew Davis <afd@...com>,
Wolfgang Grandegger <wg@...ndegger.com>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
linux-can@...r.kernel.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, netdev@...r.kernel.org,
Schuyler Patton <spatton@...com>
Subject: Re: [RFC PATCH 5/5] can: m_can: Add hrtimer to generate software
interrupt
On 4/14/23 20:20, Marc Kleine-Budde wrote:
> On 13.04.2023 17:30:51, Judith Mendez wrote:
>> Add a hrtimer to MCAN struct. Each MCAN will have its own
>> hrtimer instantiated if there is no hardware interrupt found.
>>
>> The hrtimer will generate a software interrupt every 1 ms. In
>
> Are you sure about the 1ms?
The "shortest" 11 bit CAN ID CAN frame is a Classical CAN frame with DLC
= 0 and 1 Mbit/s (arbitration) bitrate. This should be 48 bits @1Mbit =>
~50 usecs
So it should be something about
50 usecs * (FIFO queue len - 2)
if there is some FIFO involved, right?
Best regards,
Oliver
>> 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@...com>
>> ---
>> drivers/net/can/m_can/m_can.c | 24 ++++++++++++++++++++++--
>> drivers/net/can/m_can/m_can.h | 3 +++
>> drivers/net/can/m_can/m_can_platform.c | 9 +++++++--
>> 3 files changed, 32 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
>> index 8e83d6963d85..bb9d53f4d3cc 100644
>> --- a/drivers/net/can/m_can/m_can.c
>> +++ b/drivers/net/can/m_can/m_can.c
>> @@ -23,6 +23,7 @@
>> #include <linux/pinctrl/consumer.h>
>> #include <linux/platform_device.h>
>> #include <linux/pm_runtime.h>
>> +#include <linux/hrtimer.h>
>>
>> #include "m_can.h"
>>
>> @@ -1584,6 +1585,11 @@ static int m_can_close(struct net_device *dev)
>> if (!cdev->is_peripheral)
>> napi_disable(&cdev->napi);
>>
>> + if (dev->irq < 0) {
>> + dev_info(cdev->dev, "Disabling the hrtimer\n");
>
> Make it a dev_dbg() or remove completely.
>
>> + hrtimer_cancel(&cdev->hrtimer);
>> + }
>> +
>> m_can_stop(dev);
>> m_can_clk_stop(cdev);
>> free_irq(dev->irq, dev);
>> @@ -1792,6 +1798,19 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
>> return NETDEV_TX_OK;
>> }
>>
>> +enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
>> +{
>> + irqreturn_t ret;
>
> never read value?
>
>> + struct m_can_classdev *cdev =
>> + container_of(timer, struct m_can_classdev, hrtimer);
>> +
>> + ret = m_can_isr(0, cdev->net);
>> +
>> + hrtimer_forward_now(timer, ns_to_ktime(5 * NSEC_PER_MSEC));
>
> There's ms_to_ktime()....and the "5" doesn't match your patch
> description.
>
>> +
>> + return HRTIMER_RESTART;
>> +}
>> +
>> static int m_can_open(struct net_device *dev)
>> {
>> struct m_can_classdev *cdev = netdev_priv(dev);
>> @@ -1836,8 +1855,9 @@ static int m_can_open(struct net_device *dev)
>> }
>>
>> if (err < 0) {
>> - netdev_err(dev, "failed to request interrupt\n");
>> - goto exit_irq_fail;
>> + dev_info(cdev->dev, "Enabling the hrtimer\n");
>> + cdev->hrtimer.function = &hrtimer_callback;
>> + hrtimer_start(&cdev->hrtimer, ns_to_ktime(0), HRTIMER_MODE_REL_PINNED);
>
> IMHO it makes no sense to request an IRQ if the device doesn't have one,
> and then try to fix up things in the error path. What about this?
>
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -1831,9 +1831,11 @@ 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 {
> + } else if (dev->irq) {
> err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
> dev);
> + } else {
> + // polling
> }
>
> if (err < 0) {
>
>> }
>>
>> /* start the m_can controller */
>> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
>> index a839dc71dc9b..ed046d77fdb9 100644
>> --- a/drivers/net/can/m_can/m_can.h
>> +++ b/drivers/net/can/m_can/m_can.h
>> @@ -28,6 +28,7 @@
>> #include <linux/pm_runtime.h>
>> #include <linux/slab.h>
>> #include <linux/uaccess.h>
>> +#include <linux/hrtimer.h>
>>
>> /* m_can lec values */
>> enum m_can_lec_type {
>> @@ -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 9c1dcf838006..53e1648e9dab 100644
>> --- a/drivers/net/can/m_can/m_can_platform.c
>> +++ b/drivers/net/can/m_can/m_can_platform.c
>> @@ -7,6 +7,7 @@
>>
>> #include <linux/phy/phy.h>
>> #include <linux/platform_device.h>
>> +#include <linux/hrtimer.h>
>>
>> #include "m_can.h"
>>
>> @@ -98,8 +99,12 @@ static int m_can_plat_probe(struct platform_device *pdev)
>> addr = devm_platform_ioremap_resource_byname(pdev, "m_can");
>> irq = platform_get_irq_byname(pdev, "int0");
>> if (IS_ERR(addr) || irq < 0) {
>
> What about the IS_ERR(addr) case?
>
>> - ret = -EINVAL;
>> - goto probe_fail;
>> + if (irq == -EPROBE_DEFER) {
>> + ret = -EPROBE_DEFER;
>> + goto probe_fail;
>> + }
>> + dev_info(mcan_class->dev, "Failed to get irq, initialize hrtimer\n");
>> + hrtimer_init(&mcan_class->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
>
> I don't like it when polling is unconditionally set up in case of an irq
> error. I'm not sure if we need an explicit device tree property....
>
>> }
>>
>> /* message ram could be shared */
>> --
>> 2.17.1
>>
>>
>
> Marc
>
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