netdev - Re: [PATCH net-next] net: lan966x: Improve the CPU TX bitrate.

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Message-ID: <20220308164024.5f65b426@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 8 Mar 2022 16:40:24 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc:     Andrew Lunn <andrew@...n.ch>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <UNGLinuxDriver@...rochip.com>,
        <davem@...emloft.net>
Subject: Re: [PATCH net-next] net: lan966x: Improve the CPU TX bitrate.

On Tue, 8 Mar 2022 23:30:00 +0100 Horatiu Vultur wrote:
> > >  static int lan966x_port_inj_ready(struct lan966x *lan966x, u8 grp)
> > >  {
> > > -     u32 val;
> > > +     unsigned long time = jiffies + usecs_to_jiffies(READL_TIMEOUT_US);
> > > +     int ret = 0;
> > >
> > > -     return readx_poll_timeout_atomic(lan966x_port_inj_status, lan966x, val,
> > > -                                      QS_INJ_STATUS_FIFO_RDY_GET(val) & BIT(grp),
> > > -                                      READL_SLEEP_US, READL_TIMEOUT_US);
> > > +     while (!(lan_rd(lan966x, QS_INJ_STATUS) &
> > > +              QS_INJ_STATUS_FIFO_RDY_SET(BIT(grp)))) {
> > > +             if (time_after(jiffies, time)) {
> > > +                     ret = -ETIMEDOUT;
> > > +                     break;
> > > +             }  
> > 
> > Did you try setting READL_SLEEP_US to 0? readx_poll_timeout_atomic()
> > explicitly supports that.  
> 
> I have tried but it didn't improve. It was the same as before.

Huh, is ktime_get() super expensive on that platform?
jiffies vs ktime seems to be the main difference?