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Message-ID: <0f62faa4-608f-4e8e-98e5-7e6e50e20308@kernel.org>
Date: Mon, 26 Feb 2024 14:49:12 +0200
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Subject: Re: [PATCH net-next 1/2] net: ethernet: ti: am65-cpts: Enable PTP RX
 HW timestamp using CPTS FIFO
Content-Language: en-US
To: Chintan Vankar <c-vankar@ti.com>, Dan Carpenter
 <dan.carpenter@linaro.org>, Siddharth Vadapalli <s-vadapalli@ti.com>,
 Richard Cochran <richardcochran@gmail.com>, Paolo Abeni <pabeni@redhat.com>,
 Jakub Kicinski <kuba@kernel.org>, Eric Dumazet <edumazet@google.com>,
 "David S. Miller" <davem@davemloft.net>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org
References: <20240215110953.3225099-1-c-vankar@ti.com>
 <52ff5e18-3616-478a-ab40-8f9a6f7f3e37@kernel.org>
 <3713e01e-1e48-489b-8ec2-e98471ca22f0@ti.com>
From: Roger Quadros <rogerq@kernel.org>
In-Reply-To: <3713e01e-1e48-489b-8ec2-e98471ca22f0@ti.com>
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On 26/02/2024 11:08, Chintan Vankar wrote:
> 
> On 19/02/24 16:54, Roger Quadros wrote:
>>
>> On 15/02/2024 13:09, Chintan Vankar wrote:
>>> CPTS module supports capturing timestamp for every packet it receives,
>>> add a new function named "am65_cpts_rx_find_ts()" to get the timestamp
>>> of received packets from CPTS FIFO.
>>>
>>> Add another function named "am65_cpts_rx_timestamp()" which internally
>>> calls "am65_cpts_rx_find_ts()" function and timestamps the received
>>> PTP packets.
>>>
>>> Signed-off-by: Chintan Vankar <c-vankar@ti.com>
>>> ---
>>>   drivers/net/ethernet/ti/am65-cpts.c | 84 +++++++++++++++++++++--------
>>>   drivers/net/ethernet/ti/am65-cpts.h | 11 ++--
>>>   2 files changed, 67 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/ti/am65-cpts.c b/drivers/net/ethernet/ti/am65-cpts.c
>>> index c66618d91c28..92a3b40e60d6 100644
>>> --- a/drivers/net/ethernet/ti/am65-cpts.c
>>> +++ b/drivers/net/ethernet/ti/am65-cpts.c
>>> @@ -859,29 +859,6 @@ static long am65_cpts_ts_work(struct ptp_clock_info *ptp)
>>>       return delay;
>>>   }
>>>   -/**
>>> - * am65_cpts_rx_enable - enable rx timestamping
>>> - * @cpts: cpts handle
>>> - * @en: enable
>>> - *
>>> - * This functions enables rx packets timestamping. The CPTS can timestamp all
>>> - * rx packets.
>>> - */
>>> -void am65_cpts_rx_enable(struct am65_cpts *cpts, bool en)
>>> -{
>>> -    u32 val;
>>> -
>>> -    mutex_lock(&cpts->ptp_clk_lock);
>>> -    val = am65_cpts_read32(cpts, control);
>>> -    if (en)
>>> -        val |= AM65_CPTS_CONTROL_TSTAMP_EN;
>>> -    else
>>> -        val &= ~AM65_CPTS_CONTROL_TSTAMP_EN;
>>> -    am65_cpts_write32(cpts, val, control);
>>> -    mutex_unlock(&cpts->ptp_clk_lock);
>>> -}
>>> -EXPORT_SYMBOL_GPL(am65_cpts_rx_enable);
>>> -
>>>   static int am65_skb_get_mtype_seqid(struct sk_buff *skb, u32 *mtype_seqid)
>>>   {
>>>       unsigned int ptp_class = ptp_classify_raw(skb);
>>> @@ -906,6 +883,67 @@ static int am65_skb_get_mtype_seqid(struct sk_buff *skb, u32 *mtype_seqid)
>>>       return 1;
>>>   }
>>>   +static u64 am65_cpts_find_rx_ts(struct am65_cpts *cpts, struct sk_buff *skb,
>>> +                int ev_type, u32 skb_mtype_seqid)
>>> +{
>>> +    struct list_head *this, *next;
>>> +    struct am65_cpts_event *event;
>>> +    unsigned long flags;
>>> +    u32 mtype_seqid;
>>> +    u64 ns = 0;
>>> +
>>> +    am65_cpts_fifo_read(cpts);
>> am65_cpts_fifo_read() is called from the CPTS interrupt handler and the
>> event is popped out of the FIFO and pushed into an event list.
>>
>> Doesn't this race with that interrupt handler?
> Could you clarify why there be a race condition ?

I'm not sure so was asking. The question is, do you have to call
am65_cpts_fifo_read() here? If yes, could you please add a comment why.

>> Can't you use that event list instead of reading cpts_fifo directly?
>>
>> Something like am65_cpts_match_tx_ts()?
>>
>>> +    spin_lock_irqsave(&cpts->lock, flags);
>>> +    list_for_each_safe(this, next, &cpts->events) {
>>> +        event = list_entry(this, struct am65_cpts_event, list);
>>> +        if (time_after(jiffies, event->tmo)) {
>>> +            list_del_init(&event->list);
>>> +            list_add(&event->list, &cpts->pool);
>>> +            continue;
>>> +        }
>>> +
>>> +        mtype_seqid = event->event1 &
>>> +                  (AM65_CPTS_EVENT_1_MESSAGE_TYPE_MASK |
>>> +                   AM65_CPTS_EVENT_1_SEQUENCE_ID_MASK |
>>> +                   AM65_CPTS_EVENT_1_EVENT_TYPE_MASK);
>>> +
>>> +        if (mtype_seqid == skb_mtype_seqid) {
>>> +            ns = event->timestamp;
>>> +            list_del_init(&event->list);
>>> +            list_add(&event->list, &cpts->pool);
>>> +            break;
>>> +        }
>>> +    }
>>> +    spin_unlock_irqrestore(&cpts->lock, flags);
>>> +
>>> +    return ns;
>>> +}
>>> +
>>> +void am65_cpts_rx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb)
>>> +{
>>> +    struct am65_cpts_skb_cb_data *skb_cb = (struct am65_cpts_skb_cb_data *)skb->cb;
>>> +    struct skb_shared_hwtstamps *ssh;
>>> +    int ret;
>>> +    u64 ns;
>>> +
>>> +    ret = am65_skb_get_mtype_seqid(skb, &skb_cb->skb_mtype_seqid);
>>> +    if (!ret)
>>> +        return; /* if not PTP class packet */
>>> +
>>> +    skb_cb->skb_mtype_seqid |= (AM65_CPTS_EV_RX << AM65_CPTS_EVENT_1_EVENT_TYPE_SHIFT);
>>> +
>>> +    dev_dbg(cpts->dev, "%s mtype seqid %08x\n", __func__, skb_cb->skb_mtype_seqid);
>>> +
>>> +    ns = am65_cpts_find_rx_ts(cpts, skb, AM65_CPTS_EV_RX, skb_cb->skb_mtype_seqid);
>>> +    if (!ns)
>>> +        return;
>>> +
>>> +    ssh = skb_hwtstamps(skb);
>>> +    memset(ssh, 0, sizeof(*ssh));
>>> +    ssh->hwtstamp = ns_to_ktime(ns);
>>> +}
>>> +EXPORT_SYMBOL_GPL(am65_cpts_rx_timestamp);
>>> +
>>>   /**
>>>    * am65_cpts_tx_timestamp - save tx packet for timestamping
>>>    * @cpts: cpts handle
>>> diff --git a/drivers/net/ethernet/ti/am65-cpts.h b/drivers/net/ethernet/ti/am65-cpts.h
>>> index 6e14df0be113..6099d772799d 100644
>>> --- a/drivers/net/ethernet/ti/am65-cpts.h
>>> +++ b/drivers/net/ethernet/ti/am65-cpts.h
>>> @@ -22,9 +22,9 @@ void am65_cpts_release(struct am65_cpts *cpts);
>>>   struct am65_cpts *am65_cpts_create(struct device *dev, void __iomem *regs,
>>>                      struct device_node *node);
>>>   int am65_cpts_phc_index(struct am65_cpts *cpts);
>>> +void am65_cpts_rx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb);
>>>   void am65_cpts_tx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb);
>>>   void am65_cpts_prep_tx_timestamp(struct am65_cpts *cpts, struct sk_buff *skb);
>>> -void am65_cpts_rx_enable(struct am65_cpts *cpts, bool en);
>>>   u64 am65_cpts_ns_gettime(struct am65_cpts *cpts);
>>>   int am65_cpts_estf_enable(struct am65_cpts *cpts, int idx,
>>>                 struct am65_cpts_estf_cfg *cfg);
>>> @@ -48,17 +48,18 @@ static inline int am65_cpts_phc_index(struct am65_cpts *cpts)
>>>       return -1;
>>>   }
>>>   -static inline void am65_cpts_tx_timestamp(struct am65_cpts *cpts,
>>> +static inline void am65_cpts_rx_timestamp(struct am65_cpts *cpts,
>>>                         struct sk_buff *skb)
>>>   {
>>>   }
>>>   -static inline void am65_cpts_prep_tx_timestamp(struct am65_cpts *cpts,
>>> -                           struct sk_buff *skb)
>>> +static inline void am65_cpts_tx_timestamp(struct am65_cpts *cpts,
>>> +                      struct sk_buff *skb)
>>>   {
>>>   }
>>>   -static inline void am65_cpts_rx_enable(struct am65_cpts *cpts, bool en)
>>> +static inline void am65_cpts_prep_tx_timestamp(struct am65_cpts *cpts,
>>> +                           struct sk_buff *skb)
>>>   {
>>>   }
>>>   

-- 
cheers,
-roger