On 13/12/2023 13:48, Laurent Pinchart wrote:
On Wed, Dec 13, 2023 at 01:40:54PM +0200, Tomi Valkeinen wrote:
On 13/12/2023 13:23, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@xxxxxxxx>
With clang-16, building without COMMON_CLK triggers a range check on
udelay() because of a constant division-by-zero calculation:
ld.lld: error: undefined symbol: __bad_udelay
referenced by mt9m114.c
drivers/media/i2c/mt9m114.o:(mt9m114_power_on) in archive vmlinux.a
In this configuration, the driver already fails to probe, before
this function gets called, so it's enough to suppress the assertion.
Do this by using fsleep(), which turns long delays into sleep() calls
in place of the link failure.
This is probably a good idea regardless to avoid overly long dynamic
udelay() calls on a slow clock.
Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
drivers/media/i2c/mt9m114.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/i2c/mt9m114.c b/drivers/media/i2c/mt9m114.c
index 0a22f328981d..68adaecaf481 100644
--- a/drivers/media/i2c/mt9m114.c
+++ b/drivers/media/i2c/mt9m114.c
@@ -2116,7 +2116,7 @@ static int mt9m114_power_on(struct mt9m114 *sensor)
duration = DIV_ROUND_UP(2 * 50 * 1000000, freq);
gpiod_set_value(sensor->reset, 1);
- udelay(duration);
+ fsleep(duration);
gpiod_set_value(sensor->reset, 0);
} else {
/*
I think this is fine, so:
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
But: If we don't have COMMON_CLK (or rather, I think, HAVE_CLK), the
freq will be zero at compile time. So won't the compiler give a warning
for the DIV_ROUND_UP() call?
Interestingly, for me, this doesn't give a div-by-zero warning:
int x;
int y = 0;
x = DIV_ROUND_UP(10, y);
but this does:
int x;
const int y = 0;
x = DIV_ROUND_UP(10, y);
And looks like this gives the warning too:
int x;
const int y = 0;
if (y)
x = DIV_ROUND_UP(10, y);
So, I think, the code in the driver could fail to compile at some later
point, if the compiler warnings are improved (?), or if someone adds a
'const' in front of 'long freq = clk_get_rate(sensor->clk);' line.
Maybe worry about that if it actually happens =).
Maybe :-) I would be tempted to make VIDEO_CAMERA_SENSOR depend on
COMMON_CLK.
I think HAVE_CLK would be more correct.
Tomi
