Re: [PATCH] staging: fbtft: fb_watterott: fix usleep_range is preferred over udelay

On Sun, Nov 01, 2020 at 07:39:48AM +0100, Greg KH wrote:

On Sun, Nov 01, 2020 at 02:20:10AM +0200, Hassan Shahbazi wrote:

quoted

Fix the checkpath.pl issue on fb_watterott.c. write_vmem and
write_vmem_8bit functions are within non-atomic context and can
safely use usleep_range.
see Documentation/timers/timers-howto.txt

Signed-off-by: Hassan Shahbazi <redacted>
---
 drivers/staging/fbtft/fb_watterott.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/fbtft/fb_watterott.c b/drivers/staging/fbtft/fb_watterott.c
index 76b25df376b8..afcc86a17995 100644
--- a/drivers/staging/fbtft/fb_watterott.c
+++ b/drivers/staging/fbtft/fb_watterott.c

@@ -84,7 +84,7 @@ static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
 			par->txbuf.buf, 10 + par->info->fix.line_length);
 		if (ret < 0)
 			return ret;
-		udelay(300);
+		usleep_range(300, 310);
 	}
 
 	return 0;

@@ -124,7 +124,7 @@ static int write_vmem_8bit(struct fbtft_par *par, size_t offset, size_t len)
 			par->txbuf.buf, 10 + par->info->var.xres);
 		if (ret < 0)
 			return ret;
-		udelay(700);
+		usleep_range(700, 710);

How do you know that these ranges are ok?  Are you able to test these
changes with real hardware?

thanks,

greg k-h

No, I don't have the hardware to test with. I just used the current
value as the minimum and added an epsilon to it for the maximum
param.

best, hassan shahbazi