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SubjectRe: [PATCH v12 04/13] mfd: Add Ingenic TCU driver
On Wed, 26 Jun 2019, Paul Cercueil wrote:
> Le mer. 26 juin 2019 à 15:18, Lee Jones <lee.jones@linaro.org> 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@crapouillou.net>
> > > ---
> > >
> > > 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?

> 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).

> > > +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?

> > > + return !!(pwm_channels_mask & BIT(channel));
> > > +}
> > > +EXPORT_SYMBOL_GPL(ingenic_tcu_pwm_can_use_chn);

Where is this called from?

I think this needs a review by the DT guys.

> > > diff --git a/include/linux/mfd/ingenic-tcu.h
> > > b/include/linux/mfd/ingenic-tcu.h
> > > index 2083fa20821d..21df23916cd2 100644
> > > --- a/include/linux/mfd/ingenic-tcu.h
> > > +++ b/include/linux/mfd/ingenic-tcu.h
> > > @@ -6,6 +6,11 @@
> > > #define __LINUX_MFD_INGENIC_TCU_H_
> > >
> > > #include <linux/bitops.h>
> > > +#include <linux/init.h>
> > > +
> > > +struct device;
> > > +struct device_node;
> > > +struct regmap;
> > >
> > > #define TCU_REG_WDT_TDR 0x00
> > > #define TCU_REG_WDT_TCER 0x04
> > > @@ -53,4 +58,7 @@
> > > #define TCU_REG_TCNTc(c) (TCU_REG_TCNT0 + ((c) *
> > > TCU_CHANNEL_STRIDE))
> > > #define TCU_REG_TCSRc(c) (TCU_REG_TCSR0 + ((c) *
> > > TCU_CHANNEL_STRIDE))
> > >
> > > +struct regmap * __init ingenic_tcu_get_regmap(struct device_node
> > > *np);
> > > +bool ingenic_tcu_pwm_can_use_chn(struct device *dev, unsigned int
> > > channel);
> > > +
> > > #endif /* __LINUX_MFD_INGENIC_TCU_H_ */
> >
>
>

--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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