Re: [PATCH 4/8] clk: davinci: add a reset lookup table for psc0

[David Lechner]

On 03/21/2018 11:08 AM, Bartosz Golaszewski wrote:
> 2018-03-21 17:01 GMT+01:00 David Lechner <david@xxxxxxxxxxxxxx>:
> > On 03/21/2018 07:08 AM, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> > >
> > > In order to be able to use the reset framework in legacy boot mode as
> > > well, add the reset lookup table to the psc driver for da850 variant.
> > >
> > > Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> > > ---
> > >    drivers/clk/davinci/psc-da850.c | 8 ++++++++
> > >    drivers/clk/davinci/psc.c       | 1 +
> > >    2 files changed, 9 insertions(+)
> > >
> > > diff --git a/drivers/clk/davinci/psc-da850.c
> > > b/drivers/clk/davinci/psc-da850.c
> > > index ccc7eb17bf3a..395db4b2c0ee 100644
> > > --- a/drivers/clk/davinci/psc-da850.c
> > > +++ b/drivers/clk/davinci/psc-da850.c
> > > @@ -6,6 +6,7 @@
> > >     */
> > >      #include <linux/clk-provider.h>
> > > +#include <linux/reset-controller.h>
> > >    #include <linux/clk.h>
> > >    #include <linux/clkdev.h>
> > >    #include <linux/init.h>
> > > @@ -66,8 +67,15 @@ LPSC_CLKDEV3(ecap_clkdev,    "fck",  "ecap.0",
> > >                                  "fck",  "ecap.1",
> > >                                  "fck",  "ecap.2");
> > >    +static struct reset_control_lookup da850_psc0_reset_lookup_table[] = {
> > > +       RESET_LOOKUP("davinci-rproc.0", NULL, 15),
> > > +};
> > > +
> > >    static int da850_psc0_init(struct device *dev, void __iomem *base)
> > >    {
> > > +       reset_controller_add_lookup("da850-psc0",
> > > +                                   da850_psc0_reset_lookup_table,
> > > +
> > > ARRAY_SIZE(da850_psc0_reset_lookup_table));
> >
> >
> > Could there be a race condition here since you are adding the lookup
> > *before*
> > you are adding the actual provider? It seems like
> > reset_controller_add_lookup()
> > should be after davinci_psc_register_clocks().
>
> I don't think so, because reset_controller_add_lookup() only adds the
> lookup structure to the list in reset/core.c. The actual reset
> controller struct is only located and used when reset_control_get_*()
> is called, so after probing the user. And it's all protected with
> mutexes.
>
> This made me think though - maybe if we can't locate the controller,
> we should return -EPROBE_DEFER from probe in davinci-rproc?
>
> Bart

Yes, especially since we know that the PSC driver itself does get
deferred already.