On Mon, Sep 09, 2019 at 10:56:25AM +0100, Greg KH wrote: > On Sun, Sep 08, 2019 at 08:26:05PM -0500, Sreeram Veluthakkal wrote: > > This patch fixes the issue: > > FILE: drivers/staging/fbtft/fb_agm1264k-fl.c:88: > > CHECK: usleep_range is preferred over udelay; see Documentation/timers/timers-howto.rst > > + udelay(20); > > > > Signed-off-by: Sreeram Veluthakkal <srrmvlt@xxxxxxxxx> > > --- > > drivers/staging/fbtft/fb_agm1264k-fl.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/fbtft/fb_agm1264k-fl.c b/drivers/staging/fbtft/fb_agm1264k-fl.c > > index eeeeec97ad27..2dece71fd3b5 100644 > > --- a/drivers/staging/fbtft/fb_agm1264k-fl.c > > +++ b/drivers/staging/fbtft/fb_agm1264k-fl.c > > @@ -85,7 +85,7 @@ static void reset(struct fbtft_par *par) > > dev_dbg(par->info->device, "%s()\n", __func__); > > > > gpiod_set_value(par->gpio.reset, 0); > > - udelay(20); > > + usleep_range(20, 40); > > Is it "safe" to wait 40? This kind of change you can only do if you > know this is correct. Have you tested this with hardware? > > thanks, > > greg k-h Hi Greg, No I haven't tested it, I don't have the hw. I dug depeer in to the usleep_range https://github.com/torvalds/linux/blob/master/kernel/time/timer.c#L1993 u64 delta = (u64)(max - min) * NSEC_PER_USEC; * The @delta argument gives the kernel the freedom to schedule the * actual wakeup to a time that is both power and performance friendly. * The kernel give the normal best effort behavior for "@expires+@delta", * but may decide to fire the timer earlier, but no earlier than @expires. My understanding is that keeping delta 0 (min=max=20) would be equivalent. I can revise the patch to usleep_range(20, 20) or usleep_range(20, 21) for a 1 usec delta. What do you suggest? thanks, Sreeram _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
