On Wed, Sep 08, 2010 at 11:07:57AM +0800, Jason Wang wrote: > Dmitry Torokhov wrote: > >On Wed, Sep 01, 2010 at 09:48:18AM -0700, Dmitry Torokhov wrote: > >>On Wed, Sep 01, 2010 at 06:07:30PM +0800, Jason Wang wrote: > >>>Dmitry Torokhov wrote: > >>>>Hi Jason, > >>>> > >>>>On Wed, Aug 25, 2010 at 11:45:27AM +0800, Jason Wang wrote: > >>>>>Hi dmitry and others, > >>>>> > >>>>>could you please to help me review this patch? > >>>>> > >>>>>Thanks, > >>>>>Jason. > >>>>> > >>>>>Jason Wang wrote: > >>>>>>The commit 9114337 introduces regulator operations in the ads7846 > >>>>>>touchscreen driver. Among these operations, some are called in the > >>>>>>spinlock protected context. > >>>>>>On most platforms, the regulator operation is achieved through > >>>>>>i2c/spi bus transfer operations, some bus transfer operations will > >>>>>>call wait_for_completion function. It isn't allowable to call > >>>>>>sleepable function in the atomic context. So replace the spinlock with > >>>>>>mutex to protect ads7846_disable()/ads7846_enable(). > >>>>>> > >>>>I am afraid the patch is not correct. ads7846_disable() and > >>>>ads7846_enable() check and modify flags (such as irq_disabled and > >>>>pending) that are also accessed form timer/interrupt context. Moving to > >>>>mutex removes the serialization that used to be there. > >>>Thanks for your comments. you are right it is dangerous and > >>>unreasonable to use different locks to protect a critical resource. > >>>>I wonder if we should start by converting the driver to used threaded > >>>>IRQ model with "long playing" interrupt handler so all access happens in > >>>>process context and shutdown sequence is simplified. > >>>It can solve most issues, but it can't solve this situation. Because > >>>here the atomic region in which conflicts happened is from spin_lock > >>>instead of irq handler. > >>> > >>Right, but switching to threaded IRQ will allow to use mutex in place > >>of the spinlock everywhere. > >> > > > >I wonder if the following patch works (or can be made to work)... > > > Hi Dmitry, > > I have made a quick test of this patch, currently two issues found: > 1) missing #include <linux/sched.h> , it will produce a building error. > 2) touch panel can't work, it seems that the input dev doesn't > report pen up events. > Yeah, it is kinda hard to get stuff working first time around without the hardware :) > Your patch is a good frame work, i will continue working basing off > your patch. > Maybe several dates later, i will send out an extra patch to > strengthen your patch. > Great, let me know how it goes. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
