netdev - Re: [PATCH 6/7] net: dsa: b53: Add logic for TX timestamping

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Message-ID: <b884b0c1-fc60-a7ac-a788-894e206b34a9@linutronix.de>
Date:   Mon, 8 Nov 2021 10:57:48 +0100
From:   Martin Kaistra <martin.kaistra@...utronix.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Richard Cochran <richardcochran@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>
Subject: Re: [PATCH 6/7] net: dsa: b53: Add logic for TX timestamping

Am 06.11.21 um 03:50 schrieb Florian Fainelli:
> 
> 
> On 11/4/2021 6:32 AM, Martin Kaistra wrote:
>> In order to get the switch to generate a timestamp for a transmitted
>> packet, we need to set the TS bit in the BRCM tag. The switch will then
>> create a status frame, which gets send back to the cpu.
>> In b53_port_txtstamp() we put the skb into a waiting position.
>>
>> When a status frame is received, we extract the timestamp and put the 
>> time
>> according to our timecounter into the waiting skb. When
>> TX_TSTAMP_TIMEOUT is reached and we have no means to correctly get back
>> a full timestamp, we cancel the process.
>>
>> As the status frame doesn't contain a reference to the original packet,
>> only one packet with timestamp request can be sent at a time.
>>
>> Signed-off-by: Martin Kaistra <martin.kaistra@...utronix.de>
>> ---
> 
> [snip]
> 
>> +static long b53_hwtstamp_work(struct ptp_clock_info *ptp)
>> +{
>> +    struct b53_device *dev =
>> +        container_of(ptp, struct b53_device, ptp_clock_info);
>> +    struct dsa_switch *ds = dev->ds;
>> +    int i;
>> +
>> +    for (i = 0; i < ds->num_ports; i++) {
>> +        struct b53_port_hwtstamp *ps;
>> +
>> +        if (!dsa_is_user_port(ds, i))
>> +            continue;
> 
> Can you also check on !dsa_port_is_unused()?
After the currently implemented check, dp->type should be 
DSA_PORT_TYPE_USER, so it can't be DSA_PORT_TYPE_UNUSED, right?


Thanks,
Martin