Messages in this thread | | | Date | Wed, 5 Jun 2019 15:53:56 +0300 | From | Mika Westerberg <> | Subject | Re: [PATCH v2] pwm: pca9685: fix pwm/gpio inter-operation |
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On Tue, Jun 04, 2019 at 02:13:45PM -0400, Sven Van Asbroeck wrote: > This driver allows pwms to be requested as gpios via gpiolib. > Obviously, it should not be allowed to request a gpio when its > corresponding pwm is already requested (and vice versa). > So it requires some exclusion code. > > Given that the pwm and gpio cores are not synchronized with > respect to each other, this exclusion code will also require > proper synchronization. > > Such a mechanism was in place, but was inadvertently removed > by Uwe's clean-up patch. > > Upon revisiting the synchronization mechanism, we found that > theoretically, it could allow two threads to successfully > request conflicting pwms / gpios. > > Replace with a bitmap which tracks pwm in-use, plus a mutex. > As long as pwm and gpio's respective request/free functions > modify the in-use bitmap while holding the mutex, proper > synchronization will be guaranteed. > > Reported-by: YueHaibing <yuehaibing@huawei.com> > Fixes: e926b12c611c ("pwm: Clear chip_data in pwm_put()") > Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
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