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Message-ID: <20230523-crawlers-cupbearer-7a7cbfed010b-mkl@pengutronix.de>
Date: Tue, 23 May 2023 08:35:25 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Judith Mendez <jm@...com>
Cc: Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
linux-can@...r.kernel.org, Wolfgang Grandegger <wg@...ndegger.com>,
"David S . Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, Schuyler Patton <spatton@...com>,
Tero Kristo <kristo@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
Oliver Hartkopp <socketcan@...tkopp.net>,
Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH v7 2/2] can: m_can: Add hrtimer to generate software
interrupt
On 22.05.2023 21:37:49, Judith Mendez wrote:
> 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.
Please add a sentence why you introduce polling mode, i.e. there are
SoCs where the M_CAN interrupt is not available on the CPUs (which are
running Linux).
> The hrtimer 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@...com>
> ---
> Changelog:
> 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 | 33 ++++++++++++++++++++++++--
> drivers/net/can/m_can/m_can.h | 4 ++++
> drivers/net/can/m_can/m_can_platform.c | 25 ++++++++++++++++---
> 3 files changed, 57 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..f273d989bdff 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.
> @@ -895,7 +899,7 @@ static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
> netdev_dbg(dev, "Arbitration phase error detected\n");
> work_done += m_can_handle_lec_err(dev, lec);
> }
> -
> +
Unrelated change. I've send a separate patch to fix the problem.
> if (is_lec_err(dlec)) {
> netdev_dbg(dev, "Data phase error detected\n");
> work_done += m_can_handle_lec_err(dev, dlec);
> @@ -1414,6 +1418,12 @@ static int m_can_start(struct net_device *dev)
>
> m_can_enable_all_interrupts(cdev);
>
> + if (cdev->polling) {
> + dev_dbg(cdev->dev, "Start hrtimer\n");
> + hrtimer_start(&cdev->hrtimer, ms_to_ktime(HRTIMER_POLL_INTERVAL),
> + HRTIMER_MODE_REL_PINNED);
> + }
> +
> return 0;
> }
>
> @@ -1571,6 +1581,11 @@ static void m_can_stop(struct net_device *dev)
> /* disable all interrupts */
> m_can_disable_all_interrupts(cdev);
>
> + if (cdev->polling) {
> + dev_dbg(cdev->dev, "Disabling the hrtimer\n");
> + hrtimer_cancel(&cdev->hrtimer);
> + }
> +
This might be a racy. Please move the disabling of the hrtimer before
disabling all interrupts. This makes it also symmetric with respect to
m_can_start().
> /* Set init mode to disengage from the network */
> m_can_config_endisable(cdev, true);
>
> @@ -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);
> @@ -1831,9 +1858,11 @@ 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 (!cdev->polling) {
> err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
> dev);
> + } else {
> + cdev->hrtimer.function = &hrtimer_callback;
I think you can move this assignment to m_can_class_register(). We only
need to set the function once.
> }
>
> if (err < 0) {
> diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
> index a839dc71dc9b..e9db5cce4e68 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 +94,9 @@ struct m_can_classdev {
> int is_peripheral;
>
> struct mram_cfg mcfg[MRAM_CFG_NUM];
> +
> + struct hrtimer hrtimer;
> + bool polling;
> };
>
> 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..b639c9e645d3 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 +97,30 @@ 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");
I think irq will be uninitialized after this change. Although the
compiler doesn't complain :(
BTW: I think we don't need the "polling" variable in the priv. We can
make use of "irq". "irq" being 0 means use polling.
> - 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");
> + mcan_class->polling = false;
> + if (irq == -EPROBE_DEFER) {
> + ret = -EPROBE_DEFER;
> + goto probe_fail;
> + }
> + if (irq < 0) {
> + ret = -ENXIO;
Please return the original error code.
> + goto probe_fail;
> + }
> + } else {
> + mcan_class->polling = true;
> + 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) {
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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