| Message ID | 1411370675-27866-1-git-send-email-zyw@rock-chips.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Chris, Am Montag, 22. September 2014, 15:24:35 schrieb Chris Zhong: > Some device using this bus, such as regulators, they should register > as early as possible, so the I2C bus master needs to be loaded early. > Therefore initialize via subsys_initcall() is better. You could also use probe deferral in the regulator driver to wait until the bus is ready. I don't know if you're already doing it, just wanted to point that out. That said, this change will make the boot faster in any case by avoiding unnecessary deferrals, so I'm for it if you fix the minor issue below. > Signed-off-by: Chris Zhong <zyw@rock-chips.com> > > --- > > drivers/i2c/busses/i2c-rk3x.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c > index e637c32..5b91901 100644 > --- a/drivers/i2c/busses/i2c-rk3x.c > +++ b/drivers/i2c/busses/i2c-rk3x.c > @@ -760,7 +760,18 @@ static struct platform_driver rk3x_i2c_driver = { > }, > }; > > -module_platform_driver(rk3x_i2c_driver); > +static int __init rk3x_i2c_init_driver(void) > +{ > + return platform_driver_register(&rk3x_i2c_driver); > +} > + > +static void __exit rk3x_i2c_exit_driver(void) > +{ > + platform_driver_unregister(&rk3x_i2c_driver); > +} > + > +subsys_initcall(rk3x_i2c_init_driver); > +module_exit(rk3x_i2c_exit_driver); This means that the driver cannot be used as a loadable module any more, right? In that case, you should probably turn the tristate option in Kconfig into a bool. Cheers, Max
Hi Chris, > > +subsys_initcall(rk3x_i2c_init_driver); > > +module_exit(rk3x_i2c_exit_driver); > > This means that the driver cannot be used as a loadable module any more, > right? > > In that case, you should probably turn the tristate option in Kconfig into a > bool. I'm sorry, I see now that subsys_initcall() gets mapped to module_init() if the driver is built as a loadable module. Everything is fine ;-) Acked-By: Max Schwarz <max.schwarz@online.de> Cheers, Max
Max, On Mon, Sep 22, 2014 at 9:05 AM, Max Schwarz <max.schwarz@online.de> wrote: > Hi Chris, > > Am Montag, 22. September 2014, 15:24:35 schrieb Chris Zhong: >> Some device using this bus, such as regulators, they should register >> as early as possible, so the I2C bus master needs to be loaded early. >> Therefore initialize via subsys_initcall() is better. > > You could also use probe deferral in the regulator driver to wait until the > bus is ready. I don't know if you're already doing it, just wanted to point > that out. In general you are correct. You can get by with lots of probe deferrals. I don't personally know of any case where things are broken with the current code, but it's really nice to avoid the deferrals if possible. Given that this is a core SoC i2c bus and is used for _a lot_ of external connectivity (including for connecting to the primary regulator on most boards), bumping up the priority in the init order makes a lot of sense to me. This also matches the i2c busses of most other major SoCs. A selected few examples: i2c-gpio.c:subsys_initcall(i2c_gpio_init); i2c-omap.c:subsys_initcall(omap_i2c_init_driver); i2c-s3c2410.c:subsys_initcall(i2c_adap_s3c_init); i2c-tegra.c:subsys_initcall(tegra_i2c_init_driver); > That said, this change will make the boot faster in any case by avoiding > unnecessary deferrals, so I'm for it if you fix the minor issue below. Yes, I'm for it too. It's important to note that this fix is not something required for correctness (as far as I know) but just an optimization. >> Signed-off-by: Chris Zhong <zyw@rock-chips.com> >> >> --- >> >> drivers/i2c/busses/i2c-rk3x.c | 13 ++++++++++++- >> 1 file changed, 12 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c >> index e637c32..5b91901 100644 >> --- a/drivers/i2c/busses/i2c-rk3x.c >> +++ b/drivers/i2c/busses/i2c-rk3x.c >> @@ -760,7 +760,18 @@ static struct platform_driver rk3x_i2c_driver = { >> }, >> }; >> >> -module_platform_driver(rk3x_i2c_driver); >> +static int __init rk3x_i2c_init_driver(void) >> +{ >> + return platform_driver_register(&rk3x_i2c_driver); >> +} >> + >> +static void __exit rk3x_i2c_exit_driver(void) >> +{ >> + platform_driver_unregister(&rk3x_i2c_driver); >> +} >> + >> +subsys_initcall(rk3x_i2c_init_driver); >> +module_exit(rk3x_i2c_exit_driver); > > This means that the driver cannot be used as a loadable module any more, > right? > > In that case, you should probably turn the tristate option in Kconfig into a > bool. Actually, no. If this driver is switched to a loadable module then it will dumb itself down to a module initcall. ...so there's no reason for a Kconfig option. Reviewed-by: Doug Anderson <dianders@chromium.org> Tested-by: Doug Anderson <dianders@chromium.org>
Hi, > In general you are correct. You can get by with lots of probe > deferrals. I don't personally know of any case where things are > broken with the current code, but it's really nice to avoid the > deferrals if possible. Yes, we all want proper dependencies and ordering, yet deferred probing is the best we have. > Given that this is a core SoC i2c bus and is used for _a lot_ of > external connectivity (including for connecting to the primary > regulator on most boards), bumping up the priority in the init order > makes a lot of sense to me. > > This also matches the i2c busses of most other major SoCs. A selected > few examples: > > i2c-gpio.c:subsys_initcall(i2c_gpio_init); > i2c-omap.c:subsys_initcall(omap_i2c_init_driver); > i2c-s3c2410.c:subsys_initcall(i2c_adap_s3c_init); > i2c-tegra.c:subsys_initcall(tegra_i2c_init_driver); They were "lucky" to be around before deferred probing and using subsys_initcall was always considered a hack. I am not accepting new users of this hack unless there is really no other solution. So, NACK, since it doesn't solve a problem. Regards, Wolfram
diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c index e637c32..5b91901 100644 --- a/drivers/i2c/busses/i2c-rk3x.c +++ b/drivers/i2c/busses/i2c-rk3x.c @@ -760,7 +760,18 @@ static struct platform_driver rk3x_i2c_driver = { }, }; -module_platform_driver(rk3x_i2c_driver); +static int __init rk3x_i2c_init_driver(void) +{ + return platform_driver_register(&rk3x_i2c_driver); +} + +static void __exit rk3x_i2c_exit_driver(void) +{ + platform_driver_unregister(&rk3x_i2c_driver); +} + +subsys_initcall(rk3x_i2c_init_driver); +module_exit(rk3x_i2c_exit_driver); MODULE_DESCRIPTION("Rockchip RK3xxx I2C Bus driver"); MODULE_AUTHOR("Max Schwarz <max.schwarz@online.de>");
Some device using this bus, such as regulators, they should register as early as possible, so the I2C bus master needs to be loaded early. Therefore initialize via subsys_initcall() is better. Signed-off-by: Chris Zhong <zyw@rock-chips.com> --- drivers/i2c/busses/i2c-rk3x.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)