Re: [PATCH] i2c: rk3x: init module as subsys call

[Jianqun Xu]

Hi Heiko:

在 05/01/2016 15:02, Heiko Stuebner 写道:
> Hi Jianqun,
>
> Am Dienstag, 5. Januar 2016, 11:02:18 schrieb jianqun.xu:
> > From: Xu Jianqun <jay.xu@xxxxxxxxxxxxxx>
> >
> > There is a requirement from pmic device, which is on the i2c bus,
> > that the pmic needs to be called earlier then devices powered by
> > the outputs of the pmic, if not, the devices maybe fail to probe.
> >
> > For example, a pmic on i2c0, and touchscreen device on i2c2,
> > i2c0: - pmic(rk818)
> > i2c2: - ts(gt911), powered by rk818 on i2c0
> >
> > The problem will happen if the i2c2 node in dts file is ordered
> > before i2c0 node, then ts(gt911) will be probed before pmic(rk818),
> > since the power from the pmic(rk818) for ts(gt911) hasn't enabled,
> > so ts(gt911) will fail to probe due to the failure of i2c test.
> >
> > But if we set the i2c0 node before i2c2, there is no this issue.
> >
> > The stable way to make sure that pmic can be intalized before other
> > peripher devices is to make the pmic module be subsys call, the i2c
> > module need to be subsys call firstly.
>
> I do believe that came up in the past already and the direction from then
> was (and most likely still is) that drivers should make use of the probe-
> deferral mechanism instead of wiggling with the initcall ordering.
>
> Your touchscreen will have a "xyz-supply" property and I think the
> regulator-framework should already emit a -EPROBE_DEFER at regulator_get,
> when the regulator is specified but not available yet.
It seems more reasonable, thanks for advice, I will have a try.
> Heiko
>
> > Signed-off-by: Xu Jianqun <jay.xu@xxxxxxxxxxxxxx>
> > ---
> >   drivers/i2c/busses/i2c-rk3x.c | 12 +++++++++++-
> >   1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
> > index c1935eb..00e5959 100644
> > --- a/drivers/i2c/busses/i2c-rk3x.c
> > +++ b/drivers/i2c/busses/i2c-rk3x.c
> > @@ -1037,7 +1037,17 @@ static struct platform_driver rk3x_i2c_driver = {
> >   	},
> >   };
> >
> > -module_platform_driver(rk3x_i2c_driver);
> > +static int __init rk3x_i2c_init(void)
> > +{
> > +	return platform_driver_register(&rk3x_i2c_driver);
> > +}
> > +subsys_initcall(rk3x_i2c_init);
> > +
> > +static void __exit rk3x_i2c_exit(void)
> > +{
> > +	platform_driver_unregister(&rk3x_i2c_driver);
> > +}
> > +module_exit(rk3x_i2c_exit);
> >
> >   MODULE_DESCRIPTION("Rockchip RK3xxx I2C Bus driver");
> >   MODULE_AUTHOR("Max Schwarz <max.schwarz@xxxxxxxxx>");

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