[PATCH] staging: fbtft: fb_ra8875: replace udelay() with usleep_range()

[PATCH] staging: fbtft: fb_ra8875: replace udelay() with usleep_range()

[Anas Iqbal]

Replace udelay() with usleep_range() for 100 microsecond delays as
recommended by checkpatch.pl. usleep_range() avoids busy waiting and
allows the scheduler to run other tasks.

Signed-off-by: Anas Iqbal <mohd.abd.6602@gmail.com>
---
 drivers/staging/fbtft/fb_ra8875.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/fbtft/fb_ra8875.c b/drivers/staging/fbtft/fb_ra8875.c
index 0ab1de6647d0..d2400bb44f1c 100644
--- a/drivers/staging/fbtft/fb_ra8875.c
+++ b/drivers/staging/fbtft/fb_ra8875.c
@@ -210,7 +210,7 @@ static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
 	}
 	len--;
 
-	udelay(100);
+	usleep_range(100, 200);
 
 	if (len) {
 		buf = (u8 *)par->buf;
@@ -231,7 +231,7 @@ static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
 
 	/* restore user spi-speed */
 	par->fbtftops.write = fbtft_write_spi;
-	udelay(100);
+	usleep_range(100, 200);
 }
 
 static int write_vmem16_bus8(struct fbtft_par *par, size_t offset, size_t len)
-- 
2.43.0

Re: [PATCH] staging: fbtft: fb_ra8875: replace udelay() with usleep_range()

[Greg KH]

On Wed, Mar 11, 2026 at 01:52:45PM +0000, Anas Iqbal wrote:
> Replace udelay() with usleep_range() for 100 microsecond delays as
> recommended by checkpatch.pl. usleep_range() avoids busy waiting and
> allows the scheduler to run other tasks.
> 
> Signed-off-by: Anas Iqbal <mohd.abd.6602@gmail.com>
> ---
>  drivers/staging/fbtft/fb_ra8875.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/fbtft/fb_ra8875.c b/drivers/staging/fbtft/fb_ra8875.c
> index 0ab1de6647d0..d2400bb44f1c 100644
> --- a/drivers/staging/fbtft/fb_ra8875.c
> +++ b/drivers/staging/fbtft/fb_ra8875.c
> @@ -210,7 +210,7 @@ static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
>  	}
>  	len--;
>  
> -	udelay(100);
> +	usleep_range(100, 200);
>  
>  	if (len) {
>  		buf = (u8 *)par->buf;
> @@ -231,7 +231,7 @@ static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
>  
>  	/* restore user spi-speed */
>  	par->fbtftops.write = fbtft_write_spi;
> -	udelay(100);
> +	usleep_range(100, 200);
>  }
>  
>  static int write_vmem16_bus8(struct fbtft_par *par, size_t offset, size_t len)
> -- 
> 2.43.0
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- You sent a patch that has been sent multiple times in the past few
  days, and is identical to ones that has been recently rejected.
  Please always look at the mailing list traffic to determine if you are
  duplicating other people's work.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH] staging: fbtft: fb_ra8875: replace udelay() with usleep_range()

[Andy Shevchenko]

On Wed, Mar 11, 2026 at 01:52:45PM +0000, Anas Iqbal wrote:
> Replace udelay() with usleep_range() for 100 microsecond delays as
> recommended by checkpatch.pl. usleep_range() avoids busy waiting and
> allows the scheduler to run other tasks.

fsleep().
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.

-- 
With Best Regards,
Andy Shevchenko

Claude review: Re: [PATCH] staging: fbtft: fb_ra8875: replace udelay() with usleep_range()

[Claude Code Review Bot]

Overall Series Review

Subject: Re: [PATCH] staging: fbtft: fb_ra8875: replace udelay() with usleep_range()
Author: Greg KH <gregkh@linuxfoundation.org>
Patches: 3
Reviewed: 2026-03-13T14:46:08.864398

---

This is a single, straightforward cleanup patch replacing `udelay(100)` with `usleep_range(100, 200)` in a staging driver. The change is correct and follows the standard kernel coding guideline: for delays ≥ 10 µs in non-atomic context, `usleep_range()` is preferred over `udelay()` to avoid busy-waiting. Since the function performs SPI writes (which can sleep), this code is clearly in a sleepable context, making the conversion safe.

The patch is simple, well-scoped, and the commit message adequately explains the rationale.

**Verdict: Looks good (minor nit below).**

---
Generated by Claude Code Patch Reviewer

Claude review: Re: [PATCH] staging: fbtft: fb_ra8875: replace udelay() with usleep_range()

[Claude Code Review Bot]

Patch Review

**Overall: Correct and appropriate change.**

The two conversions at lines 213 and 234 of `fb_ra8875.c` are in `write_reg8_bus8()`, which is a `.write_register` callback that calls `par->fbtftops.write()` (i.e., `fbtft_write_spi`). SPI transfers can sleep, so this function is already in process context — `usleep_range()` is safe here.

```c
-	udelay(100);
+	usleep_range(100, 200);
```

The chosen range of `(100, 200)` is reasonable for a 100 µs delay.

**Minor nit (not a blocker):** The commit message says "as recommended by checkpatch.pl" — while true, it would be slightly better to mention the actual technical benefit (the function is in process/sleepable context since it performs SPI transfers) rather than citing checkpatch as the primary motivation. Checkpatch-driven patches that blindly convert `udelay` to `usleep_range` without verifying context safety are a common source of bugs; mentioning why it's safe here would strengthen the commit message.

**No functional issues found.**

---
Generated by Claude Code Patch Reviewer