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@gmail.com
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