Re: [PATCH v5 8/8] clk: fixed-rate: Convert into a module platform driver

Ricardo Ribalda Delgado
2018-10-18T20:02:24Z

Hi Alan

On Thu, Oct 18, 2018 at 9:21 PM Alan Tull <atull@kernel.org> wrote:
>
> On Tue, Jul 5, 2016 at 11:45 AM Ricardo Ribalda Delgado
> <ricardo.ribalda@gmail.com> wrote:
>
> I've stumbled across a of_node_get/put imbalance that happens when the
> fixed rate clock is added and deleted using device tree. The cause is
> that this driver calls of_clk_add_provider() when probed, but doesn't
> call of_clk_del_provider() when removed.
>
> It looks like a lot of clock drivers share that issue:
>
> $ cd drivers/clk/
> $ git grep -l of_clk_add_provider * | xargs grep -L of_clk_del_provider | wc -l
> 131
>
> It should be a one line fix, but for many files.
>
> I'm not a clock subsystem expert, so please let me know whether I'm
> missing something here.

Not an expert either, but I believe that the affected drivers are much
less. We have to consider only the drivers that can be removed

git grep -l of_clk_add_provider | xargs grep -l platform_driver |
xargs grep -l remove | xargs grep -L of_clk_del_provider
drivers/clk/clk-fixed-factor.c
drivers/clk/clk-fixed-rate.c
drivers/clk/davinci/psc.c
drivers/clk/ti/adpll.c
drivers/gpu/drm/mediatek/mtk_mt8173_hdmi_phy.c

Also there is something else that I do not undersand:
of_clk_add_hw_provider() is the same as of_clk_add_provider() ?

Maybe is a good idea to remove one of them and use the devm_of_add_hw_provider.

I can try to do that with coccinelle if you want.

Cheers

>
> Thanks,
> Alan
>
> >
> > Adds support for fixed-rate clock providers which have not been
> > enabled via of_clk_init().
> >
> > This is required by Device trees overlays that introduce clocks
> > providers.
> >
> > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> > ---
> > drivers/clk/clk-fixed-rate.c | 69 +++++++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 65 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/clk/clk-fixed-rate.c b/drivers/clk/clk-fixed-rate.c
> > index 2edb39342a02..e64ba2315880 100644
> > --- a/drivers/clk/clk-fixed-rate.c
> > +++ b/drivers/clk/clk-fixed-rate.c
> > @@ -15,6 +15,7 @@
> > #include <linux/io.h>
> > #include <linux/err.h>
> > #include <linux/of.h>
> > +#include <linux/platform_device.h>
> >
> > /*
> > * DOC: basic fixed-rate clock that cannot gate
> > @@ -160,15 +161,16 @@ EXPORT_SYMBOL_GPL(clk_hw_unregister_fixed_rate);
> > /**
> > * of_fixed_clk_setup() - Setup function for simple fixed rate clock
> > */
> > -void of_fixed_clk_setup(struct device_node *node)
> > +struct clk *_of_fixed_clk_setup(struct device_node *node)
> > {
> > struct clk *clk;
> > const char *clk_name = node->name;
> > u32 rate;
> > u32 accuracy = 0;
> > + int ret;
> >
> > if (of_property_read_u32(node, "clock-frequency", &rate))
> > - return;
> > + return ERR_PTR(-EIO);
> >
> > of_property_read_u32(node, "clock-accuracy", &accuracy);
> >
> > @@ -176,9 +178,68 @@ void of_fixed_clk_setup(struct device_node *node)
> >
> > clk = clk_register_fixed_rate_with_accuracy(NULL, clk_name, NULL,
> > 0, rate, accuracy);
> > - if (!IS_ERR(clk))
> > - of_clk_add_provider(node, of_clk_src_simple_get, clk);
> > + if (IS_ERR(clk))
> > + return clk;
> > +
> > + ret = of_clk_add_provider(node, of_clk_src_simple_get, clk);
> > + if (ret) {
> > + clk_unregister(clk);
> > + return ERR_PTR(ret);
> > + }
> > +
> > + return clk;
> > +}
> > +
> > +void of_fixed_clk_setup(struct device_node *node)
> > +{
> > + _of_fixed_clk_setup(node);
> > }
> > EXPORT_SYMBOL_GPL(of_fixed_clk_setup);
> > CLK_OF_DECLARE(fixed_clk, "fixed-clock", of_fixed_clk_setup);
> > +
> > +static int of_fixed_clk_remove(struct platform_device *pdev)
> > +{
> > + struct clk *clk = platform_get_drvdata(pdev);
> > +
> > + if (clk)
> > + clk_unregister_fixed_rate(clk);
> > +
> > + return 0;
> > +}
> > +
> > +static int of_fixed_clk_probe(struct platform_device *pdev)
> > +{
> > + struct clk *clk;
> > +
> > + /*
> > + * This function is not executed when of_fixed_clk_setup
> > + * succeeded.
> > + */
> > +
> > + clk = _of_fixed_clk_setup(pdev->dev.of_node);
> > +
> > + if (IS_ERR(clk))
> > + return PTR_ERR(clk);
> > +
> > + platform_set_drvdata(pdev, clk);
> > +
> > + return 0;
> > +}
> > +
> > +static const struct of_device_id of_fixed_clk_ids[] = {
> > + { .compatible = "fixed-clock" },
> > + { },
> > +};
> > +MODULE_DEVICE_TABLE(of, of_fixed_clk_ids);
> > +
> > +static struct platform_driver of_fixed_clk_driver = {
> > + .driver = {
> > + .name = "of_fixed_clk",
> > + .of_match_table = of_fixed_clk_ids,
> > + },
> > + .probe = of_fixed_clk_probe,
> > + .remove = of_fixed_clk_remove,
> > +};
> > +
> > +builtin_platform_driver(of_fixed_clk_driver);
> > #endif
> > --
> > 2.8.1
> >

--
Ricardo Ribalda