Messages in this thread | | | Date | Mon, 25 Aug 2014 15:49:29 +0200 | From | Thierry Reding <> | Subject | Re: [PATCH v5 3/3] pwm: i.MX: Avoid sample FIFO overflow for i.MX PWM version2 |
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On Mon, Aug 25, 2014 at 07:59:01PM +0800, Shawn Guo wrote: > On Wed, May 28, 2014 at 06:50:13PM +0800, Liu Ying wrote: > > The i.MX PWM version2 is embedded in several i.MX SoCs, > > such as i.MX27, i.MX51 and i.MX6SL. There is a 4-word(16bit) > > sample FIFO in this IP. Each FIFO slot determines the duty > > period of a PWM waveform in one full cycle. The IP spec > > mentions that we should not write a fourth sample because > > the FIFO will become full and triggers a FIFO write error > > (FWE) which will prevent the PWM from starting once it is > > enabled. In order to avoid any sample FIFO overflow issue, > > this patch clears all sample FIFO by doing software reset > > in the configuration hook when the controller is disabled > > or waits for a full PWM cycle to get a relinquished FIFO > > slot when the controller is enabled and the FIFO is fully > > loaded. > > > > The FIFO overflow issue can be reproduced by the following > > commands on the i.MX6SL EVK platform, assuming we use PWM2 > > for the debug LED which is driven by the pin HSIC_STROBE > > and the maximal brightness is 255. > > echo 0 > /sys/class/leds/user/brightness > > echo 0 > /sys/class/leds/user/brightness > > echo 0 > /sys/class/leds/user/brightness > > echo 0 > /sys/class/leds/user/brightness > > echo 255 > /sys/class/leds/user/brightness > > Here, FWE happens(PWMSR register reads 0x58) and the LED > > can not be lighten. > > > > Another way to reproduce the FIFO overflow issue is to run > > this script: > > while true; > > do echo 255 > /sys/class/leds/user/brightness; > > done > > > > Cc: Thierry Reding <thierry.reding@gmail.com> > > Cc: Sascha Hauer <s.hauer@pengutronix.de> > > Cc: Shawn Guo <shawn.guo@freescale.com> > > Cc: Lothar Waßmann <LW@KARO-electronics.de> > > Cc: linux-pwm@vger.kernel.org > > Cc: linux-arm-kernel@lists.infradead.org > > Signed-off-by: Liu Ying <Ying.Liu@freescale.com> > > The whole series, > > Acked-by: Shawn Guo <shawn.guo@freescale.com> > > Thierry, > > Can you pick them up if they look good to you?
All three patches applied with your Acked-by (and some minor reformatting of the commit message).
Thanks, Thierry [unhandled content-type:application/pgp-signature] | |