linux-kernel - Re: [PATCH net-next v6 02/25] net: dsa: qca8k: use iopoll macro for qca8k_busy

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Message-ID: <YJ8Clibm/95FOz4D@Ansuel-xps.localdomain>
Date:   Sat, 15 May 2021 01:07:02 +0200
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v6 02/25] net: dsa: qca8k: use iopoll macro for
 qca8k_busy_wait

On Fri, May 14, 2021 at 11:52:25PM +0100, Russell King (Oracle) wrote:
> On Fri, May 14, 2021 at 10:59:52PM +0200, Ansuel Smith wrote:
> > Use iopoll macro instead of while loop.
> > 
> > Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> > Reviewed-by: Andrew Lunn <andrew@...n.ch>
> 
> This doesn't look quite right to me.
> 
> >  static int
> >  qca8k_busy_wait(struct qca8k_priv *priv, u32 reg, u32 mask)
> >  {
> > -	unsigned long timeout;
> > -
> > -	timeout = jiffies + msecs_to_jiffies(20);
> > +	u32 val;
> 
> val is unsigned here.
> 
> > +	/* Check if qca8k_read has failed for a different reason
> > +	 * before returning -ETIMEDOUT
> > +	 */
> > +	if (ret < 0 && val < 0)
> 
> but here you are checking it for a negative number - this will always be
> false, making the conditional code unreachable. Either the test is wrong,
> or the type of val is wrong. Please resolve.
>

I know this is wrong and I will fix.
Anyway I tested this and I checked if with u32 a negative value was
actually provided and to my surprise the value was correctly returned.
Any idea why?

> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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