Re: [PATCH v12 04/13] mfd: Add Ingenic TCU driver

[Paul Cercueil]

Le jeu. 27 juin 2019 Ã 11:01, Lee Jones <lee.jones@xxxxxxxxxx> a 
Ãcrit :
> On Thu, 27 Jun 2019, Paul Cercueil wrote:
> >  Le jeu. 27 juin 2019 Ã 8:58, Lee Jones <lee.jones@xxxxxxxxxx> a 
> > Ãcrit :
> >  > On Wed, 26 Jun 2019, Paul Cercueil wrote:
> >  > >  Le mer. 26 juin 2019 Ã 15:18, Lee Jones 
> > <lee.jones@xxxxxxxxxx> a
> >  > > Ãcrit :
> >  > >  > 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).
>
> That makes sense.
>
> This explanation certainly belongs in the commit log.

Right.

> Can you send your v14, as you intended.  I will re-review it with new
> eyes when you do.

Could you review v13 instead? v14 will be a v13 with tiny teeny
non-code fixes (delete some newlines, replace %i with %d, and
convert the documentation from .txt to .rst).

> >  > >  > >  +bool ingenic_tcu_pwm_can_use_chn(struct device *dev, 
> > unsigned
> >  > > int
> >  > >  > > channel)
> >  > >  > >  +{
> >  > >  > >  +	const struct ingenic_soc_info *soc =
> >  > >  > > device_get_match_data(dev->parent);
> >  > >  > >  +
> >  > >  > >  +	/* Enable all TCU channels for PWM use by default except
> >  > > channels
> >  > >  > > 0/1 */
> >  > >  > >  +	u32 pwm_channels_mask = GENMASK(soc->num_channels - 1, 
> > 2);
> >  > >  > >  +
> >  > >  > >  +	device_property_read_u32(dev->parent,
> >  > > "ingenic,pwm-channels-mask",
> >  > >  > >  +				 &pwm_channels_mask);
> >  >
> >  > Doesn't this call overwrite the previous assignment above?
> >
> >  Yes, that's intended. You have a default value, that can be 
> > overriden
> >  by a device property.
>
> You should provide a comment here to make your intentions clear.

Ok.

> >  > >  > >  +	return !!(pwm_channels_mask & BIT(channel));
> >  > >  > >  +}
> >  > >  > >  +EXPORT_SYMBOL_GPL(ingenic_tcu_pwm_can_use_chn);
> >  >
> >  > Where is this called from?
> >
> >  This is called from the PWM driver.
>
> Why can't it live in the PWM driver?

It totally can. I'll move it there.

> --
> Lee Jones [æçæ]
> Linaro Services Technical Lead
> Linaro.org â Open source software for ARM SoCs
> Follow Linaro: Facebook | Twitter | Blog