netdev - Re: [PATCH NET] net: atlantic: Use readx_poll

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Date:   Wed, 19 Aug 2020 09:19:53 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Igor Russkikh <irusskikh@...vell.com>, netdev@...r.kernel.org,
        Mark Starovoytov <mstarovoitov@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH NET] net: atlantic: Use readx_poll_timeout() for large
 timeout

On Tue, Aug 18, 2020 at 06:14:39PM +0200, Sebastian Andrzej Siewior wrote:
> Commit
>    8dcf2ad39fdb2 ("net: atlantic: add hwmon getter for MAC temperature")
> 
> implemented a read callback with an udelay(10000U). This fails to
> compile on ARM because the delay is >1ms. I doubt that it is needed to
> spin for 10ms even if possible on x86.
> 
> >From looking at the code, the context appears to be preemptible so using
> usleep() should work and avoid busy spinning.
> 
> Use readx_poll_timeout() in the poll loop.
> 
> Cc: Mark Starovoytov <mstarovoitov@...vell.com>
> Cc: Igor Russkikh <irusskikh@...vell.com>
> Signed-off-by: Sebastian Andrzej Siewior <sebastian@...akpoint.cc>

Fixes: 8dcf2ad39fdb2 ("net: atlantic: add hwmon getter for MAC temperature")
Acked-by: Guenter Roeck <linux@...ck-us.net>

As in: This patch does not cause any additional trouble and will fix the
observed compile failure. However, the submitter of 8dcf2ad39fdb2 might
consider adding a mutex either into hw_atl_b0_get_mac_temp() or into
the calling code.

Thanks,
Guenter

> ---
> 
> Could someone with hardware please verify it? It compiles, yes.
> 
>  drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c b/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c
> index 16a944707ba90..8941ac4df9e37 100644
> --- a/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c
> +++ b/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c
> @@ -1631,8 +1631,8 @@ static int hw_atl_b0_get_mac_temp(struct aq_hw_s *self, u32 *temp)
>  		hw_atl_ts_reset_set(self, 0);
>  	}
>  
> -	err = readx_poll_timeout_atomic(hw_atl_b0_ts_ready_and_latch_high_get,
> -					self, val, val == 1, 10000U, 500000U);
> +	err = readx_poll_timeout(hw_atl_b0_ts_ready_and_latch_high_get, self,
> +				 val, val == 1, 10000U, 500000U);
>  	if (err)
>  		return err;
>  
> -- 
> 2.28.0
>