Re: [PATCH v2 3/6] soc: actions: Add Actions Semi Owl socinfo driver

[Cristian Ciocaltea]

On Fri, Apr 02, 2021 at 11:46:24PM +0530, Manivannan Sadhasivam wrote:
> On Tue, Mar 30, 2021 at 04:48:18PM +0300, Cristian Ciocaltea wrote:
> > The driver provides information about the Action Semi Owl family of
> > SoCs (S500, S700 and S900) to user space via sysfs: machine, family,
> > soc_id, serial_number.
> > 
> > Note the serial number is currently provided only for the S500 SoC
> > variant.
> > 
> > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxx>
> > ---
> >  drivers/soc/actions/Kconfig                   |   8 +
> >  drivers/soc/actions/Makefile                  |   1 +
> >  drivers/soc/actions/owl-socinfo.c             | 152 ++++++++++++++++++
> >  include/linux/soc/actions/owl-serial-number.h |  20 +++
> >  4 files changed, 181 insertions(+)
> >  create mode 100644 drivers/soc/actions/owl-socinfo.c
> >  create mode 100644 include/linux/soc/actions/owl-serial-number.h
> > 
> > diff --git a/drivers/soc/actions/Kconfig b/drivers/soc/actions/Kconfig
> > index 1aca2058a40c..15faade9282d 100644
> > --- a/drivers/soc/actions/Kconfig
> > +++ b/drivers/soc/actions/Kconfig
> > @@ -14,4 +14,12 @@ config OWL_PM_DOMAINS
> >  	  power-gating on Actions Semiconductor S500, S700 and S900 SoCs.
> >  	  If unsure, say 'n'.
> >  
> > +config OWL_SOCINFO
> > +	bool "Actions Semi Owl SoC info driver"
> > +	default ARCH_ACTIONS
> > +	select SOC_BUS
> > +	help
> > +	  Say 'y' here to support the Action Semiconductor Owl socinfo
> 
> Actions Semi
> 
> > +	  driver, providing information about the SoC to user space.
> > +
> >  endif
> > diff --git a/drivers/soc/actions/Makefile b/drivers/soc/actions/Makefile
> > index 4db9e7b050e5..4b2591d3089f 100644
> > --- a/drivers/soc/actions/Makefile
> > +++ b/drivers/soc/actions/Makefile
> > @@ -2,3 +2,4 @@
> >  
> >  obj-$(CONFIG_OWL_PM_DOMAINS_HELPER) += owl-sps-helper.o
> >  obj-$(CONFIG_OWL_PM_DOMAINS) += owl-sps.o
> > +obj-$(CONFIG_OWL_SOCINFO) += owl-socinfo.o
> > diff --git a/drivers/soc/actions/owl-socinfo.c b/drivers/soc/actions/owl-socinfo.c
> > new file mode 100644
> > index 000000000000..f28eafac3792
> > --- /dev/null
> > +++ b/drivers/soc/actions/owl-socinfo.c
> > @@ -0,0 +1,152 @@
> 
> [...]
> 
> > + * Access SoC's serial number stored by the bootloader in DDR memory.
> > + */
> > +static int owl_socinfo_read_serial_rmem(struct device *dev)
> > +{
> > +	struct reserved_mem *rmem;
> > +	struct device_node *np;
> > +	int ret = 0;
> > +
> > +	np = of_find_compatible_node(NULL, NULL, "actions,owl-soc-serial");
> > +	if (!np)
> > +		return -ENXIO;
> > +
> > +	rmem = of_reserved_mem_lookup(np);
> 
> If you do this correctly, you could use "pdev->dev.of_node" here instead of
> using "of_find_compatible_node()" for getting np.

Right, as previously explained, my intention was to avoid binding the
driver on the serial number node in order to keep it generic enough.

> > +	if (!rmem) {
> > +		dev_err(dev, "failed to acquire reserved memory region\n");
> > +		ret = -EINVAL;
> > +		goto out_put;
> > +	}
> > +
> 
> [...]
> 
> > +static const struct of_device_id owl_socinfo_of_match[] = {
> > +	{ .compatible = "actions,s500-soc", .data = &s500_soc_info, },
> > +	{ .compatible = "actions,s700-soc", .data = &s700_soc_info, },
> > +	{ .compatible = "actions,s900-soc", .data = &s900_soc_info, },
> 
> Please don't add S700/S900 for now.

I assumed we can use the driver for S700/S900, even though the serial
number is not provided for them.

> > +	{ }
> > +};
> > +
> > +static struct platform_driver owl_socinfo_platform_driver = {
> > +	.probe = owl_socinfo_probe,
> > +	.driver = {
> > +		.name = "owl-socinfo",
> > +		.of_match_table = owl_socinfo_of_match,
> > +	},
> > +};
> > +
> > +static int __init owl_socinfo_init(void)
> > +{
> > +	return platform_driver_register(&owl_socinfo_platform_driver);
> > +}
> > +subsys_initcall(owl_socinfo_init);
> > diff --git a/include/linux/soc/actions/owl-serial-number.h b/include/linux/soc/actions/owl-serial-number.h
> > new file mode 100644
> > index 000000000000..f8595417668f
> > --- /dev/null
> > +++ b/include/linux/soc/actions/owl-serial-number.h
> > @@ -0,0 +1,20 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +/*
> > + * Copyright (c) 2021 Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxx>
> > + */
> > +
> > +#ifndef __SOC_ACTIONS_OWL_SERIAL_NUMBER_H__
> > +#define __SOC_ACTIONS_OWL_SERIAL_NUMBER_H__
> > +
> > +#if IS_ENABLED(CONFIG_OWL_SOCINFO)
> > +u32 owl_get_soc_serial_low(void);
> > +u32 owl_get_soc_serial_high(void);
> 
> Where are these APIs used?

This will be used by the Ethernet MAC driver to generate a stable
address. Initially I used the global 'system_serial_{low,high}'
variables to pass this information outside the driver, but that is
not portable, i.e. only supported on ARM32, not ARM64.

Thanks for the review,
Cristi

> Thanks,
> Mani
> 
> > +#else
> > +static inline u32 owl_get_soc_serial_low(void)
> > +{ return 0; }
> > +
> > +static inline u32 owl_get_soc_serial_high(void)
> > +{ return 0; }
> > +#endif /* CONFIG_OWL_SOCINFO */
> > +
> > +#endif /* __SOC_ACTIONS_OWL_SERIAL_NUMBER_H__ */
> > -- 
> > 2.31.1
> >