From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Subject: Re: [PATCH] net: mdio-gpio: support access that may sleep Date: Fri, 24 Apr 2015 09:19:55 -0700 Message-ID: <553A6D2B.20901@gmail.com> References: <1429722414-18173-1-git-send-email-vivien.didelot@savoirfairelinux.com> <20150424.110455.2117537129018647564.davem@davemloft.net> <553A67B2.3040400@gmail.com> <20150424.120142.515098054679955418.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: vivien.didelot@savoirfairelinux.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@savoirfairelinux.com To: David Miller Return-path: In-Reply-To: <20150424.120142.515098054679955418.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 24/04/15 09:01, David Miller wrote: > From: Florian Fainelli > Date: Fri, 24 Apr 2015 08:56:34 -0700 > >> On 24/04/15 08:04, David Miller wrote: >>> From: Vivien Didelot >>> Date: Wed, 22 Apr 2015 13:06:54 -0400 >>> >>>> Some systems using mdio-gpio may use gpio on message based busses, which >>>> require sleeping (e.g. gpio from an I2C I/O expander). >>>> >>>> Since this driver does not use IRQ handler, it is safe to use the >>>> _cansleep suffixed gpio accessors. >>>> >>>> Signed-off-by: Vivien Didelot >>> >>> Since this is down underneath the layer of an MII bus, you cannot >>> universally say that these routines are always called in a sleepable >>> context. >>> >>> The PHY layer, and the driver itself above that, might call these >>> routines from timers, interruptes etc. >> >> The PHY library calls these routines from its state machine workqueue >> for that reason, or from process context (when invoked via ethtool >> ioctl). The only special case is phy_mac_interrupt() which is callable >> from interrupt context, but schedules the state machine workqueue anyway >> to circumvent the "in-interrupt" context. >> >> If we were not doing that, there would be a number of things broken, for >> instance the per-MDIO bus mutex would not protect us from anything. > > Does the link state polling timer use a workqueue in this manner as > well? Yes, the state machine re-schedules its own delayed workqueue at the end of its state processing, no timer/hrtimer is used. -- Florian