From mboxrd@z Thu Jan 1 00:00:00 1970 From: shawn.guo@freescale.com (Shawn Guo) Date: Mon, 22 Oct 2012 22:32:45 +0800 Subject: [PATCH v4] ARM: SMP_TWD: make setup()/stop() reentrant In-Reply-To: <1350911721-3184-1-git-send-email-linus.walleij@stericsson.com> References: <1350911721-3184-1-git-send-email-linus.walleij@stericsson.com> Message-ID: <20121022143244.GA2180@S2100-06.ap.freescale.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Oct 22, 2012 at 03:15:21PM +0200, Linus Walleij wrote: > From: Linus Walleij > > It has been brought to my knowledge that the .setup()/.stop() > function pair in the SMP TWD is going to be called from atomic > contexts for CPUs coming and going, and then the > clk_prepare()/clk_unprepare() calls cannot be called > on subsequent .setup()/.stop() iterations. This is however > just the tip of an iceberg as the function pair is not > designed to be reentrant at all. > > This change makes the SMP_TWD clock .setup()/.stop() pair reentrant > by splitting the .setup() function in three parts: > > - One COMMON part that is executed the first time the first CPU > in the TWD cluster is initialized. This will fetch the TWD > clk for the cluster and prepare+enable it. If no clk is > available it will calibrate the rate instead. > > - One part that is executed the FIRST TIME a certain CPU is > brought on-line. This initializes and sets up the clock event > for a certain CPU. > > - One part that is executed on every subsequent .setup() call. > This will re-initialize the clock event. This is augmented > to call the clk_enable()/clk_disable() pair properly. > > Cc: Shawn Guo > Reported-by: Peter Chen > Signed-off-by: Linus Walleij Tested-by: Shawn Guo