linux-kernel - Re: [RFC Patch net-next v2 3/8] net: dsa: microchip: Initial hardware time stamping support

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Date:   Thu, 24 Nov 2022 10:52:46 +0000
From:   <Arun.Ramadoss@...rochip.com>
To:     <olteanv@...il.com>
CC:     <andrew@...n.ch>, <linux-kernel@...r.kernel.org>,
        <UNGLinuxDriver@...rochip.com>, <vivien.didelot@...il.com>,
        <linux@...linux.org.uk>, <Tristram.Ha@...rochip.com>,
        <f.fainelli@...il.com>, <kuba@...nel.org>, <edumazet@...gle.com>,
        <pabeni@...hat.com>, <richardcochran@...il.com>,
        <netdev@...r.kernel.org>, <Woojung.Huh@...rochip.com>,
        <davem@...emloft.net>
Subject: Re: [RFC Patch net-next v2 3/8] net: dsa: microchip: Initial hardware
 time stamping support

On Thu, 2022-11-24 at 12:22 +0200, Vladimir Oltean wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
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> 
> On Wed, Nov 23, 2022 at 01:57:47PM +0000, Arun.Ramadoss@...rochip.com
>  wrote:
> > > What's your excuse which such a horrible code pattern? What will
> > > happen
> > > so bad with the packet if it's flagged with a TX timestamp
> > > request in
> > > KSZ_SKB_CB(skb) at the same time as REG_PTP_MSG_CONF1 is written
> > > to?
> > > 
> > > Also, doesn't dev->ports[port].hwts_tx_en serve as a guard
> > > against
> > > flagging packets for TX timestamps when you shouldn't?
> > > 
> > 
> > I took this configuration template routine from other driver.

Mistake here. It is carried forwarded from Christian Eggers patch.

> 
> Not really a good excuse. The sja1105 driver has more hardware-
> specific
> issues to deal with, not necessarily the same as ksz.
> 
> > Can I replace above snippet with
> > 
> > tagger_data->hwtstamp_set_state(dev->ds, rx_on);
> > ret = ksz_ptp_enable_mode(dev, rx_on);
> > if (ret)
> >     return ret;
> 
> Why do you need to call hwtstamp_set_state anyway?

In tag_ksz.c, xmit function query this state, to determine whether to
allocate the 4 PTP timestamp bytes in the skb_buffer or not. Using this
tagger_data set state, ptp enable and disable is communicated between
ksz_ptp.c and tag_ksz.c