linux-kernel - Re: [PATCH v2 1/1] net: fec: ptp: avoid register access when ipg clock is disabled

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Date:   Fri, 26 Feb 2021 07:23:31 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Heiko Thiery <heiko.thiery@...il.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Fugang Duan <fugang.duan@....com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH v2 1/1] net: fec: ptp: avoid register access when ipg
 clock is disabled

On Thu, Feb 25, 2021 at 10:15:16PM +0100, Heiko Thiery wrote:
> When accessing the timecounter register on an i.MX8MQ the kernel hangs.
> This is only the case when the interface is down. This can be reproduced
> by reading with 'phc_ctrl eth0 get'.
> 
> Like described in the change in 91c0d987a9788dcc5fe26baafd73bf9242b68900
> the igp clock is disabled when the interface is down and leads to a
> system hang.
> 
> So we check if the ptp clock status before reading the timecounter
> register.
> 
> Signed-off-by: Heiko Thiery <heiko.thiery@...il.com>
> ---
> v2:
>  - add mutex (thanks to Richard)
> 
> v3:
> I did a mistake and did not test properly
>  - add parenteses
>  - fix the used variable

Acked-by: Richard Cochran <richardcochran@...il.com>