* [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() @ 2023-12-13 11:23 Arnd Bergmann 2023-12-13 11:36 ` Laurent Pinchart 2023-12-13 11:40 ` Tomi Valkeinen 0 siblings, 2 replies; 6+ messages in thread From: Arnd Bergmann @ 2023-12-13 11:23 UTC (permalink / raw) To: Laurent Pinchart, Sakari Ailus, Mauro Carvalho Chehab, Nathan Chancellor, Jacopo Mondi, Hans Verkuil Cc: Arnd Bergmann, Nick Desaulniers, Bill Wendling, Justin Stitt, Tomi Valkeinen, Shuah Khan, linux-media, linux-kernel, llvm From: Arnd Bergmann <arnd@arndb.de> 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@linux.intel.com> Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- 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 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() 2023-12-13 11:23 [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() Arnd Bergmann @ 2023-12-13 11:36 ` Laurent Pinchart 2023-12-13 11:40 ` Tomi Valkeinen 1 sibling, 0 replies; 6+ messages in thread From: Laurent Pinchart @ 2023-12-13 11:36 UTC (permalink / raw) To: Arnd Bergmann Cc: Sakari Ailus, Mauro Carvalho Chehab, Nathan Chancellor, Jacopo Mondi, Hans Verkuil, Arnd Bergmann, Nick Desaulniers, Bill Wendling, Justin Stitt, Tomi Valkeinen, Shuah Khan, linux-media, linux-kernel, llvm Hi Arnd, Thank you for the patch. On Wed, Dec 13, 2023 at 12:23:07PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > 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 <sakari.ailus@linux.intel.com> > Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() 2023-12-13 11:23 [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() Arnd Bergmann 2023-12-13 11:36 ` Laurent Pinchart @ 2023-12-13 11:40 ` Tomi Valkeinen 2023-12-13 11:48 ` Laurent Pinchart 1 sibling, 1 reply; 6+ messages in thread From: Tomi Valkeinen @ 2023-12-13 11:40 UTC (permalink / raw) To: Arnd Bergmann, Laurent Pinchart, Sakari Ailus, Mauro Carvalho Chehab, Nathan Chancellor, Jacopo Mondi, Hans Verkuil Cc: Arnd Bergmann, Nick Desaulniers, Bill Wendling, Justin Stitt, Shuah Khan, linux-media, linux-kernel, llvm On 13/12/2023 13:23, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > 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@linux.intel.com> > Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > 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@ideasonboard.com> 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() 2023-12-13 11:40 ` Tomi Valkeinen @ 2023-12-13 11:48 ` Laurent Pinchart 2023-12-13 11:56 ` Tomi Valkeinen 0 siblings, 1 reply; 6+ messages in thread From: Laurent Pinchart @ 2023-12-13 11:48 UTC (permalink / raw) To: Tomi Valkeinen Cc: Arnd Bergmann, Sakari Ailus, Mauro Carvalho Chehab, Nathan Chancellor, Jacopo Mondi, Hans Verkuil, Arnd Bergmann, Nick Desaulniers, Bill Wendling, Justin Stitt, Shuah Khan, linux-media, linux-kernel, llvm 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@arndb.de> > > > > 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@linux.intel.com> > > Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor") > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > --- > > 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@ideasonboard.com> > > 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() 2023-12-13 11:48 ` Laurent Pinchart @ 2023-12-13 11:56 ` Tomi Valkeinen 2023-12-13 12:09 ` Laurent Pinchart 0 siblings, 1 reply; 6+ messages in thread From: Tomi Valkeinen @ 2023-12-13 11:56 UTC (permalink / raw) To: Laurent Pinchart Cc: Arnd Bergmann, Sakari Ailus, Mauro Carvalho Chehab, Nathan Chancellor, Jacopo Mondi, Hans Verkuil, Arnd Bergmann, Nick Desaulniers, Bill Wendling, Justin Stitt, Shuah Khan, linux-media, linux-kernel, llvm 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@arndb.de> >>> >>> 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@linux.intel.com> >>> Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor") >>> Signed-off-by: Arnd Bergmann <arnd@arndb.de> >>> --- >>> 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@ideasonboard.com> >> >> 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() 2023-12-13 11:56 ` Tomi Valkeinen @ 2023-12-13 12:09 ` Laurent Pinchart 0 siblings, 0 replies; 6+ messages in thread From: Laurent Pinchart @ 2023-12-13 12:09 UTC (permalink / raw) To: Tomi Valkeinen Cc: Arnd Bergmann, Sakari Ailus, Mauro Carvalho Chehab, Nathan Chancellor, Jacopo Mondi, Hans Verkuil, Arnd Bergmann, Nick Desaulniers, Bill Wendling, Justin Stitt, Shuah Khan, linux-media, linux-kernel, llvm 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 <arnd@arndb.de> > >>> > >>> 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@linux.intel.com> > >>> Fixes: 24d756e914fc ("media: i2c: Add driver for onsemi MT9M114 camera sensor") > >>> Signed-off-by: Arnd Bergmann <arnd@arndb.de> > >>> --- > >>> 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@ideasonboard.com> > >> > >> 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 ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-12-13 12:09 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2023-12-13 11:23 [PATCH] [v2] media: i2c: mt9m114: use fsleep() in place of udelay() Arnd Bergmann 2023-12-13 11:36 ` Laurent Pinchart 2023-12-13 11:40 ` Tomi Valkeinen 2023-12-13 11:48 ` Laurent Pinchart 2023-12-13 11:56 ` Tomi Valkeinen 2023-12-13 12:09 ` Laurent Pinchart
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