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Date: Thu, 24 Mar 2022 07:01:17 -0700
From: Richard Cochran <richardcochran@...il.com>
To: Gerhard Engleder <gerhard@...leder-embedded.com>
Cc: yangbo.lu@....com, davem@...emloft.net, kuba@...nel.org,
mlichvar@...hat.com, vinicius.gomes@...el.com,
netdev@...r.kernel.org
Subject: Re: [PATCH net-next v1 5/6] ptp: Support late timestamp determination
On Tue, Mar 22, 2022 at 10:07:21PM +0100, Gerhard Engleder wrote:
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index 54b9f54ac0b2..b7a8cf27c349 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -450,6 +450,33 @@ void ptp_cancel_worker_sync(struct ptp_clock *ptp)
> }
> EXPORT_SYMBOL(ptp_cancel_worker_sync);
>
> +ktime_t ptp_get_timestamp(int index,
> + const struct skb_shared_hwtstamps *hwtstamps,
> + bool cycles)
> +{
> + char name[PTP_CLOCK_NAME_LEN] = "";
> + struct ptp_clock *ptp;
> + struct device *dev;
> + ktime_t ts;
> +
> + snprintf(name, PTP_CLOCK_NAME_LEN, "ptp%d", index);
> + dev = class_find_device_by_name(ptp_class, name);
This seems expensive for every single Rx frame in a busy PTP network.
Can't this be cached in the socket?
> + if (!dev)
> + return 0;
> +
> + ptp = dev_get_drvdata(dev);
> +
> + if (ptp->info->gettstamp)
> + ts = ptp->info->gettstamp(ptp->info, hwtstamps, cycles);
> + else
> + ts = hwtstamps->hwtstamp;
> +
> + put_device(dev);
> +
> + return ts;
> +}
> +EXPORT_SYMBOL(ptp_get_timestamp);
> +
> /* module operations */
>
> static void __exit ptp_exit(void)
> diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
> index cc6a7b2e267d..f4f0d8a880c6 100644
> --- a/include/linux/ptp_clock_kernel.h
> +++ b/include/linux/ptp_clock_kernel.h
> @@ -133,6 +133,16 @@ struct ptp_system_timestamp {
> * parameter cts: Contains timestamp (device,system) pair,
> * where system time is realtime and monotonic.
> *
> + * @gettstamp: Get hardware timestamp based on normal/adjustable time or free
> + * running time. If @getcycles64 or @getcyclesx64 are supported,
> + * then this method is required to provide timestamps based on the
> + * free running time. This method will be called if
> + * SKBTX_HW_TSTAMP_PHC is set by the driver.
> + * parameter hwtstamps: skb_shared_hwtstamps structure pointer.
> + * parameter cycles: If false, then hardware timestamp based on
> + * normal/adjustable time is requested. If true, then hardware
> + * timestamp based on free running time is requested.
> + *
> * @enable: Request driver to enable or disable an ancillary feature.
> * parameter request: Desired resource to enable or disable.
> * parameter on: Caller passes one to enable or zero to disable.
> @@ -185,6 +195,9 @@ struct ptp_clock_info {
> struct ptp_system_timestamp *sts);
> int (*getcrosscycles)(struct ptp_clock_info *ptp,
> struct system_device_crosststamp *cts);
> + ktime_t (*gettstamp)(struct ptp_clock_info *ptp,
> + const struct skb_shared_hwtstamps *hwtstamps,
> + bool cycles);
> int (*enable)(struct ptp_clock_info *ptp,
> struct ptp_clock_request *request, int on);
> int (*verify)(struct ptp_clock_info *ptp, unsigned int pin,
> @@ -364,6 +377,19 @@ static inline void ptp_cancel_worker_sync(struct ptp_clock *ptp)
> * a loadable module.
> */
>
> +/**
> + * ptp_get_timestamp() - get timestamp of ptp clock
> + *
> + * @index: phc index of ptp pclock.
> + * @hwtstamps: skb_shared_hwtstamps structure pointer.
> + * @cycles: true for timestamp based on cycles.
> + *
> + * Returns timestamp, or 0 on error.
> + */
> +ktime_t ptp_get_timestamp(int index,
> + const struct skb_shared_hwtstamps *hwtstamps,
> + bool cycles);
> +
> /**
> * ptp_get_vclocks_index() - get all vclocks index on pclock, and
> * caller is responsible to free memory
> @@ -386,6 +412,10 @@ int ptp_get_vclocks_index(int pclock_index, int **vclock_index);
> */
> ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp, int vclock_index);
> #else
> +static inline ktime_t ptp_get_timestamp(int index,
> + const struct skb_shared_hwtstamps *hwtstamps,
> + bool cycles);
> +{ return 0; }
> static inline int ptp_get_vclocks_index(int pclock_index, int **vclock_index)
> { return 0; }
> static inline ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp,
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index f494ddbfc826..38929c113953 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -564,7 +564,10 @@ static inline bool skb_frag_must_loop(struct page *p)
> * &skb_shared_info. Use skb_hwtstamps() to get a pointer.
> */
> struct skb_shared_hwtstamps {
> - ktime_t hwtstamp;
> + union {
> + ktime_t hwtstamp;
> + void *phc_data;
needs kdoc update
> + };
> };
>
> /* Definitions for tx_flags in struct skb_shared_info */
> @@ -581,6 +584,9 @@ enum {
> /* generate hardware time stamp based on cycles if supported */
> SKBTX_HW_TSTAMP_USE_CYCLES = 1 << 3,
>
> + /* call PHC to get actual hardware time stamp */
> + SKBTX_HW_TSTAMP_PHC = 1 << 3,
> +
> /* generate wifi status information (where possible) */
> SKBTX_WIFI_STATUS = 1 << 4,
>
> diff --git a/net/socket.c b/net/socket.c
> index 2e932c058002..fe765d559086 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -804,21 +804,17 @@ static bool skb_is_swtx_tstamp(const struct sk_buff *skb, int false_tstamp)
> return skb->tstamp && !false_tstamp && skb_is_err_queue(skb);
> }
>
> -static void put_ts_pktinfo(struct msghdr *msg, struct sk_buff *skb)
> +static void put_ts_pktinfo(struct msghdr *msg, struct sk_buff *skb,
> + int if_index)
> {
> struct scm_ts_pktinfo ts_pktinfo;
> - struct net_device *orig_dev;
>
> if (!skb_mac_header_was_set(skb))
> return;
>
> memset(&ts_pktinfo, 0, sizeof(ts_pktinfo));
>
> - rcu_read_lock();
> - orig_dev = dev_get_by_napi_id(skb_napi_id(skb));
> - if (orig_dev)
> - ts_pktinfo.if_index = orig_dev->ifindex;
> - rcu_read_unlock();
> + ts_pktinfo.if_index = if_index;
>
> ts_pktinfo.pkt_length = skb->len - skb_mac_offset(skb);
> put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMPING_PKTINFO,
> @@ -838,6 +834,9 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
> int empty = 1, false_tstamp = 0;
> struct skb_shared_hwtstamps *shhwtstamps =
> skb_hwtstamps(skb);
> + struct net_device *orig_dev;
> + int if_index = 0;
> + int phc_index = -1;
> ktime_t hwtstamp;
>
> /* Race occurred between timestamp enabling and packet
> @@ -886,18 +885,32 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
> if (shhwtstamps &&
> (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
> !skb_is_swtx_tstamp(skb, false_tstamp)) {
> - if (sk->sk_tsflags & SOF_TIMESTAMPING_BIND_PHC)
> - hwtstamp = ptp_convert_timestamp(&shhwtstamps->hwtstamp,
> - sk->sk_bind_phc);
> + rcu_read_lock();
> + orig_dev = dev_get_by_napi_id(skb_napi_id(skb));
> + if (orig_dev) {
> + if_index = orig_dev->ifindex;
> + if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_PHC)
> + phc_index = ethtool_get_phc(orig_dev);
again, this is something that can be cached, no?
> + }
> + rcu_read_unlock();
> +
> + if ((skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_PHC) &&
> + (phc_index != -1))
> + hwtstamp = ptp_get_timestamp(phc_index, shhwtstamps,
> + sk->sk_tsflags & SOF_TIMESTAMPING_BIND_PHC);
> else
> hwtstamp = shhwtstamps->hwtstamp;
>
> + if (sk->sk_tsflags & SOF_TIMESTAMPING_BIND_PHC)
> + hwtstamp = ptp_convert_timestamp(&hwtstamp,
> + sk->sk_bind_phc);
> +
> if (ktime_to_timespec64_cond(hwtstamp, tss.ts + 2)) {
> empty = 0;
>
> if ((sk->sk_tsflags & SOF_TIMESTAMPING_OPT_PKTINFO) &&
> !skb_is_err_queue(skb))
> - put_ts_pktinfo(msg, skb);
> + put_ts_pktinfo(msg, skb, if_index);
> }
> }
> if (!empty) {
> --
> 2.20.1
>
Thanks,
Richard
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