[v2] staging: fbtft: Change udelay() to usleep_range()

[PATCH v2] staging: fbtft: Change udelay() to usleep_range()

Posted by Gideon Adjei 3 weeks, 4 days ago

Replace udelay() calls >= 100us with usleep_range() to avoid busy-waiting.

The delays are used in init_display() callbacks. These callbacks are
invoked by fbtft_probe_common() during the driver's probe path. the
probe path runs in process context which already uses sleeping APIs.
This makes usleep_range() safe to use in these situations.

Signed-off-by: Gideon Adjei <gideonadjei.dev@gmail.com>
---
 drivers/staging/fbtft/fb_tinylcd.c   | 2 +-
 drivers/staging/fbtft/fb_upd161704.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/fbtft/fb_tinylcd.c b/drivers/staging/fbtft/fb_tinylcd.c
index 9469248f2c50..ee8d6b10374a 100644
--- a/drivers/staging/fbtft/fb_tinylcd.c
+++ b/drivers/staging/fbtft/fb_tinylcd.c
@@ -41,7 +41,7 @@ static int init_display(struct fbtft_par *par)
 		       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, 400);
 	write_reg(par, MIPI_DCS_SET_DISPLAY_ON);
 
 	return 0;
diff --git a/drivers/staging/fbtft/fb_upd161704.c b/drivers/staging/fbtft/fb_upd161704.c
index c680160d6380..aed5cc7cabde 100644
--- a/drivers/staging/fbtft/fb_upd161704.c
+++ b/drivers/staging/fbtft/fb_upd161704.c
@@ -32,7 +32,7 @@ static int init_display(struct fbtft_par *par)
 
 	/* oscillator start */
 	write_reg(par, 0x003A, 0x0001);	/*Oscillator 0: stop, 1: operation */
-	udelay(100);
+	usleep_range(100, 200);
 
 	/* y-setting */
 	write_reg(par, 0x0024, 0x007B);	/* amplitude setting */
@@ -60,7 +60,7 @@ static int init_display(struct fbtft_par *par)
 
 	/* Power supply setting */
 	write_reg(par, 0x0019, 0x0000);	/* DC/DC output setting */
-	udelay(200);
+	usleep_range(200, 400);
 	write_reg(par, 0x001A, 0x1000);	/* DC/DC frequency setting */
 	write_reg(par, 0x001B, 0x0023);	/* DC/DC rising setting */
 	write_reg(par, 0x001C, 0x0C01);	/* Regulator voltage setting */
-- 
2.34.1

Re: [PATCH v2] staging: fbtft: Change udelay() to usleep_range()

Posted by Andy Shevchenko 3 weeks, 4 days ago

On Tue, Jan 13, 2026 at 11:06 PM Gideon Adjei <gideonadjei.dev@gmail.com> wrote:
>
> Replace udelay() calls >= 100us with usleep_range() to avoid busy-waiting.
>
> The delays are used in init_display() callbacks. These callbacks are
> invoked by fbtft_probe_common() during the driver's probe path. the
> probe path runs in process context which already uses sleeping APIs.
> This makes usleep_range() safe to use in these situations.

Nice, now can we switch to modern API, i.e. fsleep()?


-- 
With Best Regards,
Andy Shevchenko