linux-kernel - Re[2]: [PATCH v3] mfd: syscon: Add non-DT support

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Date:	Tue, 19 Feb 2013 11:03:01 +0400
From:	Alexander Shiyan <shc_work@...l.ru>
To:	Dong Aisheng <dong.aisheng@...aro.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re[2]: [PATCH v3] mfd: syscon: Add non-DT support

Hello.

Strange, but I not received an original answer from Arnd, have only this mail.

...
> >> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> >> index 4a7ed5a..3c0abcb 100644
> >> --- a/drivers/mfd/syscon.c
> >> +++ b/drivers/mfd/syscon.c
> >
> > Hi Alexander,
> >
> >>  struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
> >>  {
> >>       struct device_node *syscon_np;
> >>       struct regmap *regmap;
> >> +     struct syscon *syscon;
> >> +     struct device *dev;
> >>
> >>       syscon_np = of_find_compatible_node(NULL, NULL, s);
> >> -     if (!syscon_np)
> >> +     if (syscon_np) {
> >> +             regmap = syscon_node_to_regmap(syscon_np);
> >> +             of_node_put(syscon_np);
> >> +
> >> +             return regmap;
> >> +     }
> >> +
> >> +     /* Fallback to search by id_entry.name string */
> >> +     dev = driver_find_device(&syscon_driver.driver, NULL, (void *)s,
> >> +                              syscon_match_id);
> >> +     if (!dev)
> >>               return ERR_PTR(-ENODEV);
> >>
> >> -     regmap = syscon_node_to_regmap(syscon_np);
> >> -     of_node_put(syscon_np);
> >> +     syscon = dev_get_drvdata(dev);
> >>
> >> -     return regmap;
> >> +     return syscon->regmap;
> >>  }
> >>  EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
> >
> > Since you are not actually comparing the "compatible" property here,
> > I would suggest adding another function here,
> 
> Yes, i also think like that.

In this case we should provide two paths for drivers which can work as with DT
and without DT. In my case we can use platform_device_id.name field with
"compatible" string. My way in this case is transparency for driver which is
using "syscon".

> 
> > something like
> > syscon_regmap_lookup_by_pdevname() that you can use in device
> > drivers that are not DT-enabled.
> 
> IMHO i would like syscon_dev_to_regmap, then we do not need to
> care in case pdevname changes.
> See:
> http://www.gossamer-threads.com/lists/linux/kernel/1675210#1675210
> What do you think?

For me, I still do not understand how we get syscon_dev from driver.

> > I would also recommend enclosing
> > that function in #ifdef CONFIG_ATAGS.
> >
> > Which code do you have in mind that would call this anyway?
> > The changeset description does not really explain what ATAG
> > boot support in syscon is good for.
> >
> >> +     if (IS_ENABLED(CONFIG_OF) && np) {
> >> +             syscon->base = of_iomap(np, 0);
> >> +             if (!syscon->base)
> >> +                     return -EADDRNOTAVAIL;
> >> +
> >> +             res = &res_of;
> >> +             ret = of_address_to_resource(np, 0, res);
> >> +             if (ret) {
> >> +                     iounmap(syscon->base);
> >> +                     return ret;
> >> +             }
> >> +     } else {
> >> +             res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >> +             if (!res)
> >> +                     return -ENOENT;
> >> +
> >> +             if (!devm_request_mem_region(dev, res->start,
> >> +                                          resource_size(res),
> >> +                                          dev_name(&pdev->dev)))
> >> +                     return -EBUSY;
> >> +
> >> +             syscon->base = ioremap(res->start, resource_size(res));
> >> +             if (!syscon->base)
> >> +                     return -EADDRNOTAVAIL;
> >> +     }
> >
> > These two code paths look equivalent. Why not always use the second
> > one? Also, you might want to convert this to devm_ioremap_resource()
> > to simplify the code in the process.
> >
> 
> These two code paths have a slight difference.
> The path1 does not request the mem region, the main reason of that is we meet
> some devices register ranges used as syscon maybe overlapped with
> other exist drivers.
> e.g imx6q.dtsi
> The gpr is a few registers contained in iomuxc.
> gpr: iomuxc-gpr@...e0000 {
>         compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
>         reg = <0x020e0000 0x38>;
> };
> 
> iomuxc: iomuxc@...e0000 {
>         compatible = "fsl,imx6q-iomuxc";
>         reg = <0x020e0000 0x4000>;
> ...
> };
> 
> The iomuxc already has a pinctrl driver, so there are conflicts if both
> request the same mem region.
> 
> So i wonder maybe we also do not need request mem region in non-dt case,
> then we can only  use second code path.

So, you suggest completely remove CONFIG_OF-dependent code from "probe"?
I am not a guru in DT, is it will work correct?

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