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From: Vladimir Oltean <olteanv@gmail.com>
To: Kurt Kanzenbach <kurt@linutronix.de>
Cc: Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	netdev@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
	devicetree@vger.kernel.org,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Richard Cochran <richardcochran@gmail.com>,
	Kamil Alkhouri <kamil.alkhouri@hs-offenburg.de>,
	ilias.apalodimas@linaro.org
Subject: Re: [PATCH v4 2/7] net: dsa: Add DSA driver for Hirschmann Hellcreek switches
Date: Tue, 1 Sep 2020 17:22:43 +0300	[thread overview]
Message-ID: <20200901142243.2jrurmfmh6znosxd@skbuf> (raw)
In-Reply-To: <87y2ltegnd.fsf@kurt>

On Tue, Sep 01, 2020 at 04:05:42PM +0200, Kurt Kanzenbach wrote:
> Hi Vladimir,
> 
> On Tue Sep 01 2020, Vladimir Oltean wrote:
> > Hi Kurt,
> >
> > On Tue, Sep 01, 2020 at 02:50:09PM +0200, Kurt Kanzenbach wrote:
> [snip]
> >> +struct hellcreek {
> >> +	const struct hellcreek_platform_data *pdata;
> >> +	struct device *dev;
> >> +	struct dsa_switch *ds;
> >> +	struct hellcreek_port *ports;
> >> +	struct mutex reg_lock;	/* Switch IP register lock */
> >
> > Pardon me asking, but I went back through the previous review comments
> > and I didn't see this being asked.
> 
> It was asked multiple times, why there was a spinlock without interrupts
> being registered (see e.g. [1], [2]). I've used the spinlock variant,
> because the previously used hrtimers act like interrupts. As there are
> no timers anymore, there's no need for spinlocks and mutexes can be
> used.
> 

That, yes, I remember, but not why the reg_lock exists in the first
place.

> Florian Fainelli also asked if the reg lock can be removed
> completely. See below.
> 

Missed your answer on that.

> >
> > What is the register lock protecting against, exactly?
> 
> A lot of the register operations work by:
> 
>  * Select port, priority, vlan or counter
>  * Configure it
> 
> These sequences have to be atomic. That's what I wanted to ensure.
> 

So, let me rephrase. Is there any code path that is broken, even if only
theoretically, if you remove the reg_lock?

> Thanks,
> Kurt
> 
> [1] - https://lkml.kernel.org/netdev/def49ff6-72fe-7ca0-9e00-863c314c1c3d@gmail.com/
> [2] - https://lkml.kernel.org/netdev/20200624130318.GD7247@localhost/

Thanks,
-Vladimir

  reply	other threads:[~2020-09-01 14:33 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-01 12:50 [PATCH v4 0/7] Hirschmann Hellcreek DSA driver Kurt Kanzenbach
2020-09-01 12:50 ` [PATCH v4 1/7] net: dsa: Add tag handling for Hirschmann Hellcreek switches Kurt Kanzenbach
2020-09-01 12:50 ` [PATCH v4 2/7] net: dsa: Add DSA driver " Kurt Kanzenbach
2020-09-01 13:40   ` Vladimir Oltean
2020-09-01 14:05     ` Kurt Kanzenbach
2020-09-01 14:22       ` Vladimir Oltean [this message]
2020-09-01 15:59         ` Andrew Lunn
2020-09-01 16:36           ` Richard Cochran
2020-09-01 18:53             ` David Miller
2020-09-02  5:59               ` Kurt Kanzenbach
2020-09-01 15:11   ` kernel test robot
2020-09-01 12:50 ` [PATCH v4 3/7] net: dsa: hellcreek: Add PTP clock support Kurt Kanzenbach
2020-09-01 12:50 ` [PATCH v4 4/7] net: dsa: hellcreek: Add support for hardware timestamping Kurt Kanzenbach
2020-09-01 12:50 ` [PATCH v4 5/7] net: dsa: hellcreek: Add PTP status LEDs Kurt Kanzenbach
2020-09-03 16:32   ` Florian Fainelli
2020-09-01 12:50 ` [PATCH v4 6/7] dt-bindings: Add vendor prefix for Hirschmann Kurt Kanzenbach
2020-09-01 12:50 ` [PATCH v4 7/7] dt-bindings: net: dsa: Add documentation for Hellcreek switches Kurt Kanzenbach
2020-09-03 16:27   ` Rob Herring
2020-09-03 16:29   ` Florian Fainelli

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