staging: fbtft: fb_tinylcd: replace udelay() with usleep_range()

[PATCH] staging: fbtft: fb_tinylcd: replace udelay() with usleep_range()

Posted by Anas Iqbal 3 weeks, 6 days ago

Replace udelay() with usleep_range() for a 250 microsecond delay
as recommended by checkpatch.pl. usleep_range() avoids busy
waiting and allows the scheduler to schedule other tasks.

Signed-off-by: Anas Iqbal <mohd.abd.6602@gmail.com>
---
 drivers/staging/fbtft/fb_tinylcd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/fbtft/fb_tinylcd.c b/drivers/staging/fbtft/fb_tinylcd.c
index 9469248f2c50..51e6493b050f 100644
--- a/drivers/staging/fbtft/fb_tinylcd.c
+++ b/drivers/staging/fbtft/fb_tinylcd.c
@@ -38,10 +38,10 @@ static int init_display(struct fbtft_par *par)
 	write_reg(par, 0xE5, 0x00);
 	write_reg(par, 0xF0, 0x36, 0xA5, 0x53);
 	write_reg(par, 0xE0, 0x00, 0x35, 0x33, 0x00, 0x00, 0x00,
-		       0x00, 0x35, 0x33, 0x00, 0x00, 0x00);
+		  0x00, 0x35, 0x33, 0x00, 0x00, 0x00);
 	write_reg(par, MIPI_DCS_SET_PIXEL_FORMAT, 0x55);
 	write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE);
-	udelay(250);
+	usleep_range(250, 500);
 	write_reg(par, MIPI_DCS_SET_DISPLAY_ON);
 
 	return 0;
-- 
2.43.0

Re: [PATCH] staging: fbtft: fb_tinylcd: replace udelay() with usleep_range()

Posted by Andy Shevchenko 3 weeks, 6 days ago

On Wed, Mar 11, 2026 at 02:24:07PM +0000, Anas Iqbal wrote:
> Replace udelay() with usleep_range() for a 250 microsecond delay
> as recommended by checkpatch.pl. usleep_range() avoids busy
> waiting and allows the scheduler to schedule other tasks.

Now, read README here:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/staging/fbtft/README
and act accordingly.

If you have been mentored on this, show the above link to your mentors.

...

>  	write_reg(par, 0xE0, 0x00, 0x35, 0x33, 0x00, 0x00, 0x00,
> -		       0x00, 0x35, 0x33, 0x00, 0x00, 0x00);
> +		  0x00, 0x35, 0x33, 0x00, 0x00, 0x00);

Use the common sense here. This change won't be accepted.

...

> -	udelay(250);
> +	usleep_range(250, 500);

No.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] staging: fbtft: fb_tinylcd: replace udelay() with usleep_range()

Posted by Greg KH 3 weeks, 6 days ago

On Wed, Mar 11, 2026 at 02:24:07PM +0000, Anas Iqbal wrote:
> Replace udelay() with usleep_range() for a 250 microsecond delay
> as recommended by checkpatch.pl. usleep_range() avoids busy
> waiting and allows the scheduler to schedule other tasks.
> 
> Signed-off-by: Anas Iqbal <mohd.abd.6602@gmail.com>
> ---
>  drivers/staging/fbtft/fb_tinylcd.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/fbtft/fb_tinylcd.c b/drivers/staging/fbtft/fb_tinylcd.c
> index 9469248f2c50..51e6493b050f 100644
> --- a/drivers/staging/fbtft/fb_tinylcd.c
> +++ b/drivers/staging/fbtft/fb_tinylcd.c
> @@ -38,10 +38,10 @@ static int init_display(struct fbtft_par *par)
>  	write_reg(par, 0xE5, 0x00);
>  	write_reg(par, 0xF0, 0x36, 0xA5, 0x53);
>  	write_reg(par, 0xE0, 0x00, 0x35, 0x33, 0x00, 0x00, 0x00,
> -		       0x00, 0x35, 0x33, 0x00, 0x00, 0x00);
> +		  0x00, 0x35, 0x33, 0x00, 0x00, 0x00);

Don't you think the original formatting makes more sense?  And you did
not describe this change in the changelog :(

>  	write_reg(par, MIPI_DCS_SET_PIXEL_FORMAT, 0x55);
>  	write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE);
> -	udelay(250);
> +	usleep_range(250, 500);

This is a totally different change than above.  And also one that keeps
getting rejected, please see the mailing list archives for details.

thanks,

greg k-h

Re: [PATCH] staging: fbtft: fb_tinylcd: replace udelay() with usleep_range()

Posted by Dan Carpenter 3 weeks, 6 days ago

On Wed, Mar 11, 2026 at 02:24:07PM +0000, Anas Iqbal wrote:
> Replace udelay() with usleep_range() for a 250 microsecond delay
> as recommended by checkpatch.pl. usleep_range() avoids busy
> waiting and allows the scheduler to schedule other tasks.
> 
> Signed-off-by: Anas Iqbal <mohd.abd.6602@gmail.com>
> ---
>  drivers/staging/fbtft/fb_tinylcd.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/fbtft/fb_tinylcd.c b/drivers/staging/fbtft/fb_tinylcd.c
> index 9469248f2c50..51e6493b050f 100644
> --- a/drivers/staging/fbtft/fb_tinylcd.c
> +++ b/drivers/staging/fbtft/fb_tinylcd.c
> @@ -38,10 +38,10 @@ static int init_display(struct fbtft_par *par)
>  	write_reg(par, 0xE5, 0x00);
>  	write_reg(par, 0xF0, 0x36, 0xA5, 0x53);
>  	write_reg(par, 0xE0, 0x00, 0x35, 0x33, 0x00, 0x00, 0x00,
> -		       0x00, 0x35, 0x33, 0x00, 0x00, 0x00);
> +		  0x00, 0x35, 0x33, 0x00, 0x00, 0x00);

Don't do this.
1) It's unrelated.
2) The previous alignment was done deliberate to make it easier to read.
   Checkpatch is not perfect so don't always do what it says.

>  	write_reg(par, MIPI_DCS_SET_PIXEL_FORMAT, 0x55);
>  	write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE);
> -	udelay(250);
> +	usleep_range(250, 500);

Do a search for init_display on lore

https://lore.kernel.org/all/?q=init_display

regards,
dan carpenter