Le jeu. 27 juin 2019 à 8:58, Lee Jones <lee.jones@xxxxxxxxxx> a
écrit :
> On Wed, 26 Jun 2019, Paul Cercueil wrote:
> > Le mer. 26 juin 2019 à 15:18, Lee Jones
<lee.jones@xxxxxxxxxx> a
> > écrit :
> > > On Tue, 21 May 2019, Paul Cercueil wrote:
> > >
> > > > This driver will provide a regmap that can be retrieved
very
> > early
> > > > in
> > > > the boot process through the API function
> > ingenic_tcu_get_regmap().
> > > >
> > > > Additionally, it will call devm_of_platform_populate() so
that
> > all
> > > > the
> > > > children devices will be probed.
> > > >
> > > > Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> > > > ---
> > > >
> > > > Notes:
> > > > v12: New patch
> > > >
> > > > drivers/mfd/Kconfig | 8 +++
> > > > drivers/mfd/Makefile | 1 +
> > > > drivers/mfd/ingenic-tcu.c | 113
> > > > ++++++++++++++++++++++++++++++++
> > > > include/linux/mfd/ingenic-tcu.h | 8 +++
> > > > 4 files changed, 130 insertions(+)
> > > > create mode 100644 drivers/mfd/ingenic-tcu.c
>
> [...]
>
> > > > +static struct regmap * __init
ingenic_tcu_create_regmap(struct
> > > > device_node *np)
> > > > +{
> > > > + struct resource res;
> > > > + void __iomem *base;
> > > > + struct regmap *map;
> > > > +
> > > > + if (!of_match_node(ingenic_tcu_of_match, np))
> > > > + return ERR_PTR(-EINVAL);
>
> Drop this check.
>
> > > > + base = of_io_request_and_map(np, 0, "TCU");
> > > > + if (IS_ERR(base))
> > > > + return ERR_PTR(PTR_ERR(base));
> > > > +
> > > > + map = regmap_init_mmio(NULL, base,
> > &ingenic_tcu_regmap_config);
> > > > + if (IS_ERR(map))
> > > > + goto err_iounmap;
>
> Place this inside probe().
>
> > > > + return map;
> > > > +
> > > > +err_iounmap:
> > > > + iounmap(base);
> > > > + of_address_to_resource(np, 0, &res);
> > > > + release_mem_region(res.start, resource_size(&res));
> > > > +
> > > > + return map;
> > > > +}
> > >
> > > Why does this need to be set-up earlier than probe()?
> >
> > See the explanation below.
>
> I think the answer is, it doesn't.
>
> > > > +static int __init ingenic_tcu_probe(struct
platform_device
> > *pdev)
> > > > +{
> > > > + struct regmap *map =
> > ingenic_tcu_get_regmap(pdev->dev.of_node);
> > > > +
> > > > + platform_set_drvdata(pdev, map);
> > > > +
> > > > + regmap_attach_dev(&pdev->dev, map,
> > &ingenic_tcu_regmap_config);
> > > > +
> > > > + return devm_of_platform_populate(&pdev->dev);
> > > > +}
> > > > +
> > > > +static struct platform_driver ingenic_tcu_driver = {
> > > > + .driver = {
> > > > + .name = "ingenic-tcu",
> > > > + .of_match_table = ingenic_tcu_of_match,
> > > > + },
> > > > +};
> > > > +
> > > > +static int __init ingenic_tcu_platform_init(void)
> > > > +{
> > > > + return platform_driver_probe(&ingenic_tcu_driver,
> > > > + ingenic_tcu_probe);
> > >
> > > What? Why?
> >
> > The device driver probed here will populate the children
devices,
> > which will be able to retrieve the pointer to the regmap
through
> > device_get_regmap(dev->parent).
>
> I've never heard of this call. Where is it?
dev_get_regmap, in <linux/regmap.h>.
> > The children devices are normal platform drivers that can be
probed
> > the normal way. These are the PWM driver, the watchdog driver,
and
> > the
> > OST (OS Timer) clocksource driver, all part of the same
hardware
> > block
> > (the Timer/Counter Unit or TCU).
>
> If they are normal devices, then there is no need to roll your own
> regmap-getter implementation like this.
>
> > > > +}
> > > > +subsys_initcall(ingenic_tcu_platform_init);
> > > > +
> > > > +struct regmap * __init ingenic_tcu_get_regmap(struct
> > device_node
> > > > *np)
> > > > +{
> > > > + if (!tcu_regmap)
> > > > + tcu_regmap = ingenic_tcu_create_regmap(np);
> > > > +
> > > > + return tcu_regmap;
> > > > +}
> > >
> > > This makes me pretty uncomfortable.
> > >
> > > What calls it?
> >
> > The TCU IRQ driver (patch [06/13]), clocks driver (patch
[05/13]),
> > and the
> > non-OST clocksource driver (patch [07/13]) all probe very
early in
> > the boot
> > process, and share the same devicetree node. They call this
> > function to get
> > a pointer to the regmap.
>
> Horrible!
>
> Instead, you should send it through platform_set_drvdata() and
collect
> it in the child drivers with platform_get_drvdata(dev->parent).
The IRQ, clocks and clocksource driver do NOT have a "struct
device" to
begin with. They are not platform drivers, and cannot be platform
drivers,
as they must register so early in the boot process, before "struct
device"
is even a thing.
All they get is a pointer to the same devicetree node. Since all of
these
have to use the same registers, they need to use a shared regmap,
which
they obtain by calling ingenic_tcu_get_regmap() below.
Then, when this driver's probe gets called, the regmap is retrieved
and
attached to the struct device, and then the children devices will be
probed: the watchdog device, the PWM device, the OST device. These
three
will retrieve the regmap by calling dev_get_regmap(dev->parent,
NULL).
