Message-ID: <20220928204040.GA142099@hopium>
Date:   Wed, 28 Sep 2022 22:40:40 +0200
From:   Matej Vasilevski <matej.vasilevski@...nam.cz>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     Pavel Pisa <pisa@....felk.cvut.cz>,
        Ondrej Ille <ondrej.ille@...il.com>,
        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>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v4 2/3] can: ctucanfd: add HW timestamps to RX and error
 CAN frames

On Mon, Sep 19, 2022 at 12:36:21PM +0200, Marc Kleine-Budde wrote:
> On 15.09.2022 01:39:43, Matej Vasilevski wrote:
> > This patch adds support for retrieving hardware timestamps to RX and
> > error CAN frames. It uses timecounter and cyclecounter structures,
> > because the timestamping counter width depends on the IP core integration
> > (it might not always be 64-bit).
> > For platform devices, you should specify "ts-clk" clock in device tree.
> > For PCI devices, the timestamping frequency is assumed to be the same
> > as bus frequency.
> 
> Looks quite good now. Thanks for your work! Comments inline.
> 
> regards,
> Marc
> 

Hello Marc,

thanks for another thorough review from you. Please excuse the late
reply, I had a very busy schedule last week.

For the next patch version I'll revert the changes I've done to runtime
PM handling, and add dependency on PM to Kconfig.
I have confirmation from Pavel Pisa that Kconfig dependency on PM is OK
for now.

----
Also regarding your second email, thanks for letting me know that shift
of 1 isn't enough.
> +		work_delay_ns = clocksource_cyc2ns(max_cycles, priv->cc.mult,
> +						   priv->cc.shift) >> 1;
----


> > 
> > Signed-off-by: Matej Vasilevski <matej.vasilevski@...nam.cz>
> > ---
> >  drivers/net/can/ctucanfd/Makefile             |   2 +-
> >  drivers/net/can/ctucanfd/ctucanfd.h           |  20 ++
> >  drivers/net/can/ctucanfd/ctucanfd_base.c      | 239 ++++++++++++++++--
> >  drivers/net/can/ctucanfd/ctucanfd_pci.c       |   5 +-
> >  drivers/net/can/ctucanfd/ctucanfd_platform.c  |   5 +-
> >  drivers/net/can/ctucanfd/ctucanfd_timestamp.c |  70 +++++
> >  6 files changed, 318 insertions(+), 23 deletions(-)
> >  create mode 100644 drivers/net/can/ctucanfd/ctucanfd_timestamp.c
> > 
> > diff --git a/drivers/net/can/ctucanfd/Makefile b/drivers/net/can/ctucanfd/Makefile
> > index 8078f1f2c30f..a36e66f2cea7 100644
> > --- a/drivers/net/can/ctucanfd/Makefile
> > +++ b/drivers/net/can/ctucanfd/Makefile
> > @@ -4,7 +4,7 @@
> >  #
> >  
> >  obj-$(CONFIG_CAN_CTUCANFD) := ctucanfd.o
> > -ctucanfd-y := ctucanfd_base.o
> > +ctucanfd-y := ctucanfd_base.o ctucanfd_timestamp.o
> >  
> >  obj-$(CONFIG_CAN_CTUCANFD_PCI) += ctucanfd_pci.o
> >  obj-$(CONFIG_CAN_CTUCANFD_PLATFORM) += ctucanfd_platform.o
> > diff --git a/drivers/net/can/ctucanfd/ctucanfd.h b/drivers/net/can/ctucanfd/ctucanfd.h
> > index 0e9904f6a05d..b3ee583234b0 100644
> > --- a/drivers/net/can/ctucanfd/ctucanfd.h
> > +++ b/drivers/net/can/ctucanfd/ctucanfd.h
> > @@ -23,6 +23,10 @@
> >  #include <linux/netdevice.h>
> >  #include <linux/can/dev.h>
> >  #include <linux/list.h>
> > +#include <linux/timecounter.h>
> > +#include <linux/workqueue.h>
> > +
> > +#define CTUCANFD_MAX_WORK_DELAY_SEC 3600U
> >  
> >  enum ctu_can_fd_can_registers;
> >  
> > @@ -51,6 +55,15 @@ struct ctucan_priv {
> >  	u32 rxfrm_first_word;
> >  
> >  	struct list_head peers_on_pdev;
> > +
> > +	struct cyclecounter cc;
> > +	struct timecounter tc;
> > +	spinlock_t tc_lock; /* spinlock to guard access tc->cycle_last */
> > +	struct delayed_work timestamp;
> > +	struct clk *timestamp_clk;
> > +	unsigned long work_delay_jiffies;
> > +	bool timestamp_enabled;
> > +	bool timestamp_possible;
> >  };
> >  
> >  /**
> > @@ -78,5 +91,12 @@ int ctucan_probe_common(struct device *dev, void __iomem *addr,
> >  
> >  int ctucan_suspend(struct device *dev) __maybe_unused;
> >  int ctucan_resume(struct device *dev) __maybe_unused;
> > +int ctucan_runtime_resume(struct device *dev) __maybe_unused;
> > +int ctucan_runtime_suspend(struct device *dev) __maybe_unused;
> 
> These functions are exported, so they are always "used".

removed

> > +u64 ctucan_read_timestamp_cc_wrapper(const struct cyclecounter *cc);
> > +u64 ctucan_read_timestamp_counter(struct ctucan_priv *priv);
> > +void ctucan_skb_set_timestamp(struct ctucan_priv *priv, struct sk_buff *skb, u64 timestamp);
> > +void ctucan_timestamp_init(struct ctucan_priv *priv);
> > +void ctucan_timestamp_stop(struct ctucan_priv *priv);
> >  #endif /*__CTUCANFD__*/
> > diff --git a/drivers/net/can/ctucanfd/ctucanfd_base.c b/drivers/net/can/ctucanfd/ctucanfd_base.c
> > index 3c18d028bd8c..ba1a27c62ff1 100644
> > --- a/drivers/net/can/ctucanfd/ctucanfd_base.c
> > +++ b/drivers/net/can/ctucanfd/ctucanfd_base.c
> > @@ -18,6 +18,7 @@
> >   ******************************************************************************/
> >  
> >  #include <linux/clk.h>
> > +#include <linux/clocksource.h>
> >  #include <linux/errno.h>
> >  #include <linux/ethtool.h>
> >  #include <linux/init.h>
> > @@ -25,6 +26,7 @@
> >  #include <linux/interrupt.h>
> >  #include <linux/io.h>
> >  #include <linux/kernel.h>
> > +#include <linux/math64.h>
> >  #include <linux/module.h>
> >  #include <linux/skbuff.h>
> >  #include <linux/string.h>
> > @@ -148,6 +150,27 @@ static void ctucan_write_txt_buf(struct ctucan_priv *priv, enum ctu_can_fd_can_r
> >  	priv->write_reg(priv, buf_base + offset, val);
> >  }
> >  
> > +static inline u64 ctucan_concat_tstamp(u32 high, u32 low)
> > +{
> > +	return ((u64)high << 32) | ((u64)low);
> > +}
> > +
> > +u64 ctucan_read_timestamp_counter(struct ctucan_priv *priv)
> > +{
> > +	u32 ts_low;
> > +	u32 ts_high;
> > +	u32 ts_high2;
> > +
> > +	ts_high = ctucan_read32(priv, CTUCANFD_TIMESTAMP_HIGH);
> > +	ts_low = ctucan_read32(priv, CTUCANFD_TIMESTAMP_LOW);
> > +	ts_high2 = ctucan_read32(priv, CTUCANFD_TIMESTAMP_HIGH);
> > +
> > +	if (ts_high2 != ts_high)
> > +		ts_low = priv->read_reg(priv, CTUCANFD_TIMESTAMP_LOW);
> > +
> > +	return ctucan_concat_tstamp(ts_high2, ts_low) & priv->cc.mask;
> 
> I think you don't need to apply the mask. The tc will take care of this.

Yes, the masking in timecounter_cyc2time() is enough. Removed the
masking here.

> > +}
> > +
> >  #define CTU_CAN_FD_TXTNF(priv) (!!FIELD_GET(REG_STATUS_TXNF, ctucan_read32(priv, CTUCANFD_STATUS)))
> >  #define CTU_CAN_FD_ENABLED(priv) (!!FIELD_GET(REG_MODE_ENA, ctucan_read32(priv, CTUCANFD_MODE)))
> >  
> > @@ -640,12 +663,16 @@ static netdev_tx_t ctucan_start_xmit(struct sk_buff *skb, struct net_device *nde
> >   * @priv:	Pointer to CTU CAN FD's private data
> >   * @cf:		Pointer to CAN frame struct
> >   * @ffw:	Previously read frame format word
> > + * @skb:	Pointer to buffer to store timestamp
> >   *
> >   * Note: Frame format word must be read separately and provided in 'ffw'.
> >   */
> > -static void ctucan_read_rx_frame(struct ctucan_priv *priv, struct canfd_frame *cf, u32 ffw)
> > +static void ctucan_read_rx_frame(struct ctucan_priv *priv, struct canfd_frame *cf,
> > +				 u32 ffw, u64 *timestamp)
> >  {
> >  	u32 idw;
> > +	u32 tstamp_high;
> > +	u32 tstamp_low;
> >  	unsigned int i;
> >  	unsigned int wc;
> >  	unsigned int len;
> > @@ -682,9 +709,10 @@ static void ctucan_read_rx_frame(struct ctucan_priv *priv, struct canfd_frame *c
> >  	if (unlikely(len > wc * 4))
> >  		len = wc * 4;
> >  
> > -	/* Timestamp - Read and throw away */
> > -	ctucan_read32(priv, CTUCANFD_RX_DATA);
> > -	ctucan_read32(priv, CTUCANFD_RX_DATA);
> > +	/* Timestamp */
> > +	tstamp_low = ctucan_read32(priv, CTUCANFD_RX_DATA);
> > +	tstamp_high = ctucan_read32(priv, CTUCANFD_RX_DATA);
> > +	*timestamp = ctucan_concat_tstamp(tstamp_high, tstamp_low) & priv->cc.mask;
> 
> same here
> 

Removed.

> >  
> >  	/* Data */
> >  	for (i = 0; i < len; i += 4) {
> > @@ -713,6 +741,7 @@ static int ctucan_rx(struct net_device *ndev)
> >  	struct net_device_stats *stats = &ndev->stats;
> >  	struct canfd_frame *cf;
> >  	struct sk_buff *skb;
> > +	u64 timestamp;
> >  	u32 ffw;
> >  
> >  	if (test_bit(CTUCANFD_FLAG_RX_FFW_BUFFERED, &priv->drv_flags)) {
> > @@ -736,7 +765,9 @@ static int ctucan_rx(struct net_device *ndev)
> >  		return 0;
> >  	}
> >  
> > -	ctucan_read_rx_frame(priv, cf, ffw);
> > +	ctucan_read_rx_frame(priv, cf, ffw, &timestamp);
> > +	if (priv->timestamp_enabled)
> > +		ctucan_skb_set_timestamp(priv, skb, timestamp);
> >  
> >  	stats->rx_bytes += cf->len;
> >  	stats->rx_packets++;
> > @@ -906,6 +937,11 @@ static void ctucan_err_interrupt(struct net_device *ndev, u32 isr)
> >  	if (skb) {
> >  		stats->rx_packets++;
> >  		stats->rx_bytes += cf->can_dlc;
> > +		if (priv->timestamp_enabled) {
> > +			u64 tstamp = ctucan_read_timestamp_counter(priv);
> > +
> > +			ctucan_skb_set_timestamp(priv, skb, tstamp);
> > +		}
> >  		netif_rx(skb);
> >  	}
> >  }
> > @@ -951,6 +987,11 @@ static int ctucan_rx_poll(struct napi_struct *napi, int quota)
> >  			cf->data[1] |= CAN_ERR_CRTL_RX_OVERFLOW;
> >  			stats->rx_packets++;
> >  			stats->rx_bytes += cf->can_dlc;
> > +			if (priv->timestamp_enabled) {
> > +				u64 tstamp = ctucan_read_timestamp_counter(priv);
> > +
> > +				ctucan_skb_set_timestamp(priv, skb, tstamp);
> > +			}
> >  			netif_rx(skb);
> >  		}
> >  
> > @@ -1200,9 +1241,9 @@ static int ctucan_open(struct net_device *ndev)
> >  	struct ctucan_priv *priv = netdev_priv(ndev);
> >  	int ret;
> >  
> > -	ret = pm_runtime_get_sync(priv->dev);
> > +	ret = pm_runtime_resume_and_get(priv->dev);
> 
> Note, the semantics of pm_runtime_get_sync() and pm_runtime_get_sync() changed!

Oof, somehow I thought it is 1:1 replacement, even thought 20 lines
below the docstring I could see the code for resume_and_get is different.

I'll revert the changes for the next patch version and leave runtime PM
handling for another patch.

> 
> >  	if (ret < 0) {
> > -		netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n",
> > +		netdev_err(ndev, "%s: pm_runtime_resume_and_get failed(%d)\n",
> >  			   __func__, ret);
> >  		pm_runtime_put_noidle(priv->dev);
> 
> ...you must not call pm_runtime_put_noidle() if
> pm_runtime_resume_and_get() fails.
> 
> Maybe it's worth to move the runtime pm handling in a separate patch.
> 
Yes, I'll leave it for another patch.

> >  		return ret;
> > @@ -1231,6 +1272,9 @@ static int ctucan_open(struct net_device *ndev)
> >  		goto err_chip_start;
> >  	}
> >  
> > +	if (priv->timestamp_possible)
> > +		ctucan_timestamp_init(priv);
> > +
> >  	netdev_info(ndev, "ctu_can_fd device registered\n");
> >  	napi_enable(&priv->napi);
> >  	netif_start_queue(ndev);
> > @@ -1263,6 +1307,8 @@ static int ctucan_close(struct net_device *ndev)
> >  	ctucan_chip_stop(ndev);
> >  	free_irq(ndev->irq, ndev);
> >  	close_candev(ndev);
> > +	if (priv->timestamp_possible)
> > +		ctucan_timestamp_stop(priv);
> >  
> >  	pm_runtime_put(priv->dev);
> >  
> > @@ -1282,9 +1328,9 @@ static int ctucan_get_berr_counter(const struct net_device *ndev, struct can_ber
> >  	struct ctucan_priv *priv = netdev_priv(ndev);
> >  	int ret;
> >  
> > -	ret = pm_runtime_get_sync(priv->dev);
> > +	ret = pm_runtime_resume_and_get(priv->dev);
> 
> ...same here

will be left for another patch

> 
> >  	if (ret < 0) {
> > -		netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n", __func__, ret);
> > +		netdev_err(ndev, "%s: pm_runtime_resume_and_get failed(%d)\n", __func__, ret);
> >  		pm_runtime_put_noidle(priv->dev);
> 
> ..same here

will be left for another patch

> 
> >  		return ret;
> >  	}
> > @@ -1295,15 +1341,83 @@ static int ctucan_get_berr_counter(const struct net_device *ndev, struct can_ber
> >  	return 0;
> >  }
> >  
> > +static int ctucan_hwtstamp_set(struct net_device *dev, struct ifreq *ifr)
> > +{
> > +	struct ctucan_priv *priv = netdev_priv(dev);
> > +	struct hwtstamp_config cfg;
> > +
> > +	if (!priv->timestamp_possible)
> > +		return -EOPNOTSUPP;
> > +
> > +	if (copy_from_user(&cfg, ifr->ifr_data, sizeof(cfg)))
> > +		return -EFAULT;
> > +
> > +	if (cfg.flags)
> > +		return -EINVAL;
> 
> Do we have to add this check to the generic can_eth_ioctl_hwts()
> function?
> 

I kept the cfg.flags check, because it fits the spirit of the generic
ioctl function - the user has to request specifically only the supported
combination, otherwise the driver will return an error.

I don't know, I probably wouldn't add it to the generic ioctl (too
restrictive for my taste). So I should remove the flags check here,
to match the generic ioctl behaviour closely.

> > +
> > +	if (cfg.rx_filter == HWTSTAMP_FILTER_NONE && cfg.tx_type == HWTSTAMP_TX_OFF) {
> > +		priv->timestamp_enabled = false;
> > +		return 0;
> > +	} else if (cfg.rx_filter == HWTSTAMP_FILTER_ALL && cfg.tx_type == HWTSTAMP_TX_ON) {
> 
> What happens if the user only configures RX _or_ TX timestamping?
> 

Then the user gets error, same as they would get from the generic
can_eth_ioctl_hwts().

> > +		priv->timestamp_enabled = true;
> > +		return 0;
> > +	} else {
> > +		return -ERANGE;
> > +	}
> 
> nitpick: please remove else, as they are not needed after the return.

Removed.

> > +}
> > +
> > +static int ctucan_hwtstamp_get(struct net_device *dev, struct ifreq *ifr)
> > +{
> > +	struct ctucan_priv *priv = netdev_priv(dev);
> > +	struct hwtstamp_config cfg;
> > +
> > +	if (!priv->timestamp_possible)
> > +		return -EOPNOTSUPP;
> > +
> > +	cfg.flags = 0;
> > +	cfg.tx_type = priv->timestamp_enabled ? HWTSTAMP_TX_ON : HWTSTAMP_TX_OFF;
> > +	cfg.rx_filter = priv->timestamp_enabled ? HWTSTAMP_FILTER_ALL : HWTSTAMP_FILTER_NONE;
> > +
> > +	return copy_to_user(ifr->ifr_data, &cfg, sizeof(cfg)) ? -EFAULT : 0;
> 
> nitpick: please don't use the '?' operator.

Rewritten.

> 
> > +}
> > +
> > +static int ctucan_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
> > +{
> > +	switch (cmd) {
> > +	case SIOCSHWTSTAMP:
> > +		return ctucan_hwtstamp_set(dev, ifr);
> > +	case SIOCGHWTSTAMP:
> > +		return ctucan_hwtstamp_get(dev, ifr);
> > +	default:
> > +		return -EOPNOTSUPP;
> > +	}
> > +}
> > +
> > +static int ctucan_ethtool_get_ts_info(struct net_device *ndev,
> > +				      struct ethtool_ts_info *info)
> > +{
> > +	struct ctucan_priv *priv = netdev_priv(ndev);
> > +
> > +	if (!priv->timestamp_possible)
> > +		return ethtool_op_get_ts_info(ndev, info);
> > +
> > +	can_ethtool_op_get_ts_info_hwts(ndev, info);
> > +	info->rx_filters |= BIT(HWTSTAMP_FILTER_NONE);
> > +	info->tx_types |= BIT(HWTSTAMP_TX_OFF);
> > +
> > +	return 0;
> > +}
> > +
> >  static const struct net_device_ops ctucan_netdev_ops = {
> >  	.ndo_open	= ctucan_open,
> >  	.ndo_stop	= ctucan_close,
> >  	.ndo_start_xmit	= ctucan_start_xmit,
> >  	.ndo_change_mtu	= can_change_mtu,
> > +	.ndo_eth_ioctl	= ctucan_ioctl,
> >  };
> >  
> >  static const struct ethtool_ops ctucan_ethtool_ops = {
> > -	.get_ts_info = ethtool_op_get_ts_info,
> > +	.get_ts_info = ctucan_ethtool_get_ts_info,
> >  };
> >  
> >  int ctucan_suspend(struct device *dev)
> > @@ -1338,12 +1452,42 @@ int ctucan_resume(struct device *dev)
> >  }
> >  EXPORT_SYMBOL(ctucan_resume);
> >  
> > +int ctucan_runtime_suspend(struct device *dev)
> > +{
> > +	struct net_device *ndev = dev_get_drvdata(dev);
> > +	struct ctucan_priv *priv = netdev_priv(ndev);
> > +
> > +	if (!IS_ERR_OR_NULL(priv->timestamp_clk))
> > +		clk_disable_unprepare(priv->timestamp_clk);
> 
> The common clock framework handles NULL pointers, so remove the
> IS_ERR_OR_NULL().

Removed.

> 
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(ctucan_runtime_suspend);
> > +
> > +int ctucan_runtime_resume(struct device *dev)
> > +{
> > +	struct net_device *ndev = dev_get_drvdata(dev);
> > +	struct ctucan_priv *priv = netdev_priv(ndev);
> > +	int ret;
> > +
> > +	if (!IS_ERR_OR_NULL(priv->timestamp_clk)) {
> 
> ...same here

Removed.

> 
> > +		ret = clk_prepare_enable(priv->timestamp_clk);
> > +		if (ret) {
> > +			dev_err(dev, "Cannot enable timestamping clock: %d\n", ret);
> > +			return ret;
> > +		}
> > +	}
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(ctucan_runtime_resume);
> > +
> >  int ctucan_probe_common(struct device *dev, void __iomem *addr, int irq, unsigned int ntxbufs,
> >  			unsigned long can_clk_rate, int pm_enable_call,
> >  			void (*set_drvdata_fnc)(struct device *dev, struct net_device *ndev))
> >  {
> >  	struct ctucan_priv *priv;
> >  	struct net_device *ndev;
> > +	u32 timestamp_freq = 0;
> 
> nitpick: name this _rate, similar to can_clk_rate.
> 

Renamed.

> > +	u32 timestamp_bit_size = 0;
> >  	int ret;
> >  
> >  	/* Create a CAN device instance */
> > @@ -1373,6 +1517,7 @@ int ctucan_probe_common(struct device *dev, void __iomem *addr, int irq, unsigne
> >  					| CAN_CTRLMODE_FD_NON_ISO
> >  					| CAN_CTRLMODE_ONE_SHOT;
> >  	priv->mem_base = addr;
> > +	priv->timestamp_possible = true;
> >  
> >  	/* Get IRQ for the device */
> >  	ndev->irq = irq;
> > @@ -1386,27 +1531,39 @@ int ctucan_probe_common(struct device *dev, void __iomem *addr, int irq, unsigne
> >  
> >  	/* Getting the can_clk info */
> >  	if (!can_clk_rate) {
> > -		priv->can_clk = devm_clk_get(dev, NULL);
> > +		priv->can_clk = devm_clk_get_optional(dev, "core-clk");
> > +		if (!priv->can_clk)
> > +			/* For compatibility with (older) device trees without clock-names */
> > +			priv->can_clk = devm_clk_get(dev, NULL);
> >  		if (IS_ERR(priv->can_clk)) {
> > -			dev_err(dev, "Device clock not found.\n");
> > +			dev_err(dev, "Device clock not found: %pe.\n", priv->can_clk);
> >  			ret = PTR_ERR(priv->can_clk);
> >  			goto err_free;
> >  		}
> >  		can_clk_rate = clk_get_rate(priv->can_clk);
> >  	}
> >  
> > +	/* If it's a platform device - get the timestamping clock */
> > +	if (pm_enable_call) {
> 
> The variable pm_enable_call feels wrong. As PCI device automatically do
> an automatic pm_runtime_enable(), better move the pm_runtime_enable() to
> the platform device driver. But that's a separate patch.
> 
> Please don't wire more functionality to pm_enable_call. What about:
> - if ctucan_probe_common() is called with can_clk_rate set, use it as the
>   timestamp_freq, too.
> - otherwise get the rate from the ts-clk, or core clock
> 

Ok, I'll rewrite it. I agree that the pm_enable_call feels wrong.

> > +		priv->timestamp_clk = devm_clk_get(dev, "ts-clk");
> > +		if (IS_ERR(priv->timestamp_clk)) {
> > +			/* Take the core clock instead */
> > +			dev_info(dev, "Failed to get ts clk\nl");
>                                                            ^^^
> 
> trailing 'l'

Removed.

> 
> > +			priv->timestamp_clk = priv->can_clk;
> > +		}
> > +		clk_prepare_enable(priv->timestamp_clk);
> 
> Later in this function there is a call to pm_runtime_put(dev). Without
> runtime PM the clock will not turned off. So you rely on runtime PM,
> please adjust your Kconfig accordingly.

I wanted to keep the clock running (to support systems without runtime
PM - keep the clock running from probe and disable_unprepare it only
finally in the device _remove())

But scratch that, the next patch version will be with PM dependency in
Kconfig.

> 
> > +		timestamp_freq = clk_get_rate(priv->timestamp_clk);
> > +	} else {
> > +		/* PCI device: assume tstamp freq is equal to bus clk rate */
> > +		timestamp_freq = can_clk_rate;
> > +	}
> > +
> >  	priv->write_reg = ctucan_write32_le;
> >  	priv->read_reg = ctucan_read32_le;
> >  
> > +	pm_runtime_get_noresume(dev);
> 
> I think you're missing a pm_runtime_set_active() call here.

Yes, it is missing.
But I'll revert those changes for next patch version, and do only the
minimal necessary changes to runtime PM, leaving the rest of PM changes
for another patch.

> 
> >  	if (pm_enable_call)
> >  		pm_runtime_enable(dev);
> > -	ret = pm_runtime_get_sync(dev);
> > -	if (ret < 0) {
> > -		netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n",
> > -			   __func__, ret);
> > -		pm_runtime_put_noidle(priv->dev);
> > -		goto err_pmdisable;
> > -	}
> >  
> >  	/* Check for big-endianity and set according IO-accessors */
> >  	if ((ctucan_read32(priv, CTUCANFD_DEVICE_ID) & 0xFFFF) != CTUCANFD_ID) {
> > @@ -1425,6 +1582,49 @@ int ctucan_probe_common(struct device *dev, void __iomem *addr, int irq, unsigne
> >  
> >  	priv->can.clock.freq = can_clk_rate;
> >  
> > +	/* Obtain timestamping counter bit size */
> > +	timestamp_bit_size = FIELD_GET(REG_ERR_CAPT_TS_BITS,
> > +				       ctucan_read32(priv, CTUCANFD_ERR_CAPT));
> > +
> > +	/* The register value is actually bit_size - 1 */
> > +	if (timestamp_bit_size) {
> > +		timestamp_bit_size += 1;
> > +	} else {
> > +		/* For 2.x versions of the IP core, we will assume 64-bit counter
> > +		 * if there was a 0 in the register.
> > +		 */
> > +		u32 version_reg = ctucan_read32(priv, CTUCANFD_DEVICE_ID);
> > +		u32 major = FIELD_GET(REG_DEVICE_ID_VER_MAJOR, version_reg);
> > +
> > +		if (major == 2)
> > +			timestamp_bit_size = 64;
> > +		else
> > +			priv->timestamp_possible = false;
> > +	}
> > +
> > +	/* Setup conversion constants and work delay */
> > +	priv->cc.mask = CYCLECOUNTER_MASK(timestamp_bit_size);
> > +	if (priv->timestamp_possible) {
> > +		u64 max_cycles;
> > +		u64 work_delay_ns;
> > +		u32 maxsec = min_t(u32, CTUCANFD_MAX_WORK_DELAY_SEC,
> > +				   div_u64(priv->cc.mask, timestamp_freq));
> > +
> > +		priv->cc.read = ctucan_read_timestamp_cc_wrapper;
> > +		clocks_calc_mult_shift(&priv->cc.mult, &priv->cc.shift,
> > +				       timestamp_freq, NSEC_PER_SEC, maxsec);
> > +
> > +		/* shortened copy of clocks_calc_max_nsecs() */
> > +		max_cycles = div_u64(ULLONG_MAX, priv->cc.mult);
> > +		max_cycles = min(max_cycles, priv->cc.mask);
> > +		work_delay_ns = clocksource_cyc2ns(max_cycles, priv->cc.mult,
> > +						   priv->cc.shift) >> 1;
> > +		priv->work_delay_jiffies = nsecs_to_jiffies(work_delay_ns);
> > +
> > +		if (priv->work_delay_jiffies == 0)
> > +			priv->timestamp_possible = false;
> > +	}
> > +
> >  	netif_napi_add(ndev, &priv->napi, ctucan_rx_poll, NAPI_POLL_WEIGHT);
> >  
> >  	ret = register_candev(ndev);
> > @@ -1442,7 +1642,6 @@ int ctucan_probe_common(struct device *dev, void __iomem *addr, int irq, unsigne
> >  
> >  err_deviceoff:
> >  	pm_runtime_put(priv->dev);
> > -err_pmdisable:
> >  	if (pm_enable_call)
> >  		pm_runtime_disable(dev);
> >  err_free:
> > diff --git a/drivers/net/can/ctucanfd/ctucanfd_pci.c b/drivers/net/can/ctucanfd/ctucanfd_pci.c
> > index 8f2956a8ae43..bdb7cf789776 100644
> > --- a/drivers/net/can/ctucanfd/ctucanfd_pci.c
> > +++ b/drivers/net/can/ctucanfd/ctucanfd_pci.c
> > @@ -271,7 +271,10 @@ static void ctucan_pci_remove(struct pci_dev *pdev)
> >  	kfree(bdata);
> >  }
> >  
> > -static SIMPLE_DEV_PM_OPS(ctucan_pci_pm_ops, ctucan_suspend, ctucan_resume);
> > +static const struct dev_pm_ops ctucan_pci_pm_ops = {
> > +	SET_SYSTEM_SLEEP_PM_OPS(ctucan_suspend, ctucan_resume)
> > +	SET_RUNTIME_PM_OPS(ctucan_runtime_suspend, ctucan_runtime_resume, NULL)
> > +};
> >  
> >  static const struct pci_device_id ctucan_pci_tbl[] = {
> >  	{PCI_DEVICE_DATA(TEDIA, CTUCAN_VER21,
> > diff --git a/drivers/net/can/ctucanfd/ctucanfd_platform.c b/drivers/net/can/ctucanfd/ctucanfd_platform.c
> > index 89d54c2151e1..1b2052aec2ab 100644
> > --- a/drivers/net/can/ctucanfd/ctucanfd_platform.c
> > +++ b/drivers/net/can/ctucanfd/ctucanfd_platform.c
> > @@ -104,7 +104,10 @@ static int ctucan_platform_remove(struct platform_device *pdev)
> >  	return 0;
> >  }
> >  
> > -static SIMPLE_DEV_PM_OPS(ctucan_platform_pm_ops, ctucan_suspend, ctucan_resume);
> > +static const struct dev_pm_ops ctucan_platform_pm_ops = {
> > +	SET_SYSTEM_SLEEP_PM_OPS(ctucan_suspend, ctucan_resume)
> > +	SET_RUNTIME_PM_OPS(ctucan_runtime_suspend, ctucan_runtime_resume, NULL)
> > +};
> >  
> >  /* Match table for OF platform binding */
> >  static const struct of_device_id ctucan_of_match[] = {
> > diff --git a/drivers/net/can/ctucanfd/ctucanfd_timestamp.c b/drivers/net/can/ctucanfd/ctucanfd_timestamp.c
> > new file mode 100644
> > index 000000000000..77e461d1962d
> > --- /dev/null
> > +++ b/drivers/net/can/ctucanfd/ctucanfd_timestamp.c
> > @@ -0,0 +1,70 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*******************************************************************************
> > + *
> > + * CTU CAN FD IP Core
> > + *
> > + * Copyright (C) 2022 Matej Vasilevski <matej.vasilevski@...nam.cz> FEE CTU
> > + *
> > + * Project advisors:
> > + *     Jiri Novak <jnovak@....cvut.cz>
> > + *     Pavel Pisa <pisa@....felk.cvut.cz>
> > + *
> > + * Department of Measurement         (http://meas.fel.cvut.cz/)
> > + * Faculty of Electrical Engineering (http://www.fel.cvut.cz)
> > + * Czech Technical University        (http://www.cvut.cz/)
> > + ******************************************************************************/
> > +
> > +#include "linux/spinlock.h"
> > +#include <linux/bitops.h>
> > +#include <linux/clocksource.h>
> > +#include <linux/math64.h>
> > +#include <linux/timecounter.h>
> > +#include <linux/workqueue.h>
> > +
> > +#include "ctucanfd.h"
> > +#include "ctucanfd_kregs.h"
> > +
> > +u64 ctucan_read_timestamp_cc_wrapper(const struct cyclecounter *cc)
> > +{
> > +	struct ctucan_priv *priv;
> 
> Please add a "lockdep_assert_held(&priv->tc_lock);" and compile your
> code with lockdep enabled.

Didn't know about that, I'll add it, thanks.

> 
> > +
> > +	priv = container_of(cc, struct ctucan_priv, cc);
> > +	return ctucan_read_timestamp_counter(priv);
> > +}
> > +
> > +static void ctucan_timestamp_work(struct work_struct *work)
> > +{
> > +	struct delayed_work *delayed_work = to_delayed_work(work);
> > +	struct ctucan_priv *priv = container_of(delayed_work, struct ctucan_priv, timestamp);
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&priv->tc_lock, flags);
> > +	timecounter_read(&priv->tc);
> > +	spin_unlock_irqrestore(&priv->tc_lock, flags);
> > +	schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
> > +}
> > +
> > +void ctucan_skb_set_timestamp(struct ctucan_priv *priv, struct sk_buff *skb, u64 timestamp)
> > +{
> > +	struct skb_shared_hwtstamps *hwtstamps = skb_hwtstamps(skb);
> > +	u64 ns;
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&priv->tc_lock, flags);
> > +	ns = timecounter_cyc2time(&priv->tc, timestamp);
> > +	spin_unlock_irqrestore(&priv->tc_lock, flags);
> > +	hwtstamps->hwtstamp = ns_to_ktime(ns);
> > +}
> > +
> > +void ctucan_timestamp_init(struct ctucan_priv *priv)
> > +{
> > +	spin_lock_init(&priv->tc_lock);
> 
> please lock ->tc_lock during timecounter_init(), too. This will keep the
> lockdep_assert_held() happy.
> 

I'll add it.

> > +	timecounter_init(&priv->tc, &priv->cc, ktime_get_real_ns());
> > +	INIT_DELAYED_WORK(&priv->timestamp, ctucan_timestamp_work);
> > +	schedule_delayed_work(&priv->timestamp, priv->work_delay_jiffies);
> > +}
> > +
> > +void ctucan_timestamp_stop(struct ctucan_priv *priv)
> > +{
> > +	cancel_delayed_work_sync(&priv->timestamp);
> > +}
> > -- 
> > 2.25.1
> > 
> > 
> 
> -- 
> Pengutronix e.K.                 | Marc Kleine-Budde           |
> Embedded Linux                   | https://www.pengutronix.de  |
> Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
> Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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