netdev - Re: [PATCH net-next v3 2/3] net: txgbe: Reset hardware

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Message-ID: <Y0TM+eHBtGa0YLXq@lunn.ch>
Date:   Tue, 11 Oct 2022 03:55:05 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Jiawen Wu <jiawenwu@...stnetic.com>
Cc:     netdev@...r.kernel.org, mengyuanlou@...-swift.com
Subject: Re: [PATCH net-next v3 2/3] net: txgbe: Reset hardware

> > So you have an IO barrier before and a read barrier afterwards.  So all i think you need is a
> mb(), not a
> > full rd32().
> > 
> >    Andrew
> > 
> 
> I think we need a readl(), because there are problems that sometimes IO is not synchronized with
> flushing memory on some domestic cpu platforms.
> It can become a serious problem, causing register error configurations.
 
So please document this as a comment in the code.

I also then start to wounder if more such flushes are needed, to
handle this broken hardware. Do you have a detailed description of
what actually goes wrong? Otherwise how do you know when such a flush
is needed?

   Andrew