From: Arnd Bergmann <[email protected]>
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 <[email protected]>
Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor")
Signed-off-by: Arnd Bergmann <[email protected]>
---
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 {
/*
--
2.39.2
Hi Arnd,
Thank you for the patch.
On Wed, Dec 13, 2023 at 12:23:07PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> 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.
The longest delay would be 16.66µs, which may not be worth a sleep, but
I think that's fine. Using fsleep() by default is a good idea.
> Cc: Sakari Ailus <[email protected]>
> Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
Reviewed-by: Laurent Pinchart <[email protected]>
> 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 {
> /*
--
Regards,
Laurent Pinchart
On 13/12/2023 13:23, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> 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 <[email protected]>
> Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> 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 <[email protected]>
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 =).
Tomi
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 <[email protected]>
> >
> > 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 <[email protected]>
> > Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor")
> > Signed-off-by: Arnd Bergmann <[email protected]>
> > ---
> > 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 <[email protected]>
>
> 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.
--
Regards,
Laurent Pinchart
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 <[email protected]>
>>>
>>> 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 <[email protected]>
>>> Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor")
>>> Signed-off-by: Arnd Bergmann <[email protected]>
>>> ---
>>> 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 <[email protected]>
>>
>> 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
On Wed, Dec 13, 2023 at 01:56:48PM +0200, Tomi Valkeinen wrote:
> 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 <[email protected]>
> >>>
> >>> 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 <[email protected]>
> >>> Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor")
> >>> Signed-off-by: Arnd Bergmann <[email protected]>
> >>> ---
> >>> 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 <[email protected]>
> >>
> >> 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.
Indeed. Only arch/m68k (for Coldfire), arch/mips (for BCM63xx and
Lantiq) and arch/sh (for pre-DT platforms) still make use of
HAVE_LEGACY_CLK. It takes a long time to address the last users of a
legacy API, but it seems we could get there one day.
--
Regards,
Laurent Pinchart