Messages in this thread | | | Date | Wed, 16 Dec 2015 16:55:00 +0100 | From | Thierry Reding <> | Subject | Re: [PATCH v2] pwm: ftm: fix clock enable/disable when using PM |
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On Mon, Nov 23, 2015 at 02:45:07PM -0800, Stefan Agner wrote: > A FTM PWM instance enables/disables three clocks: The bus clock, the > counter clock and the PWM clock. The bus clock gets enabled on > pwm_request, whereas the counter and PWM clocks will be enabled upon > pwm_enable. > > The driver has three closesly related issues when enabling/disabling > clocks during suspend/resume: > - The three clocks are not treated differently in regards to the > individual PWM state enabled/requested. This can lead to clocks > getting disabled which have not been enabled in the first place > (a PWM channel which only has been requested going through > suspend/resume). > > - When entering suspend, the current behavior relies on the > FTM_OUTMASK register: If a PWM output is unmasked, the driver > assumes the clocks are enabled. However, some PWM instances > have only 2 channels connected (e.g. Vybrid's FTM1). In that case, > the FTM_OUTMASK reads 0x3 if all channels are disabled, even if > the code wrote 0xff to it before. For those PWM instances, the > current approach to detect enabled PWM signals does not work. > > - A third issue applies to the bus clock only, which can get enabled > multiple times (once for each PWM channel of a PWM chip). This is > fine, however when entering suspend mode, the clock only gets > disabled once. > > This change introduces a different approach by relying on the enable > and prepared counters of the clock framework and using the frameworks > PWM signal states to address all three issues. > > Clocks get disabled during suspend and back enabled on resume > regarding to the PWM channels individual state (requested/enabled). > > Since we do not count the clock enables in the driver, this change no > longer clears the Status and Control registers Clock Source Selection > (FTM_SC[CLKS]). However, since we disable the selected clock anyway, > and we explicitly select the clock source on reenabling a PWM channel > this approach should not make a difference in practice. > > Signed-off-by: Stefan Agner <stefan@agner.ch> > --- > Hi Lee, > > I just found your new email address. Thierry and I already had some > discussion about the patch here: > http://thread.gmane.org/gmane.linux.pwm/2878 > > Could you have a look at that patch? > > Changes since v1: > - Use the pwm_is_enabled helper > > drivers/pwm/pwm-fsl-ftm.c | 58 ++++++++++++++++++++--------------------------- > 1 file changed, 25 insertions(+), 33 deletions(-)
Applied, thanks.
Thierry [unhandled content-type:application/pgp-signature] | |