Subject: [PATCH 1/9] ARM: sunxi: introduce SoC identification support

From: [email-masked] (Emilio López)
Date: Sun, 03 Aug 2014 18:45:37 -0300

Hi Maxime,

Thanks for taking the time to review this :)

El 03/08/14 a las 09:40, Maxime Ripard escibi?:
> Hi Emilio,
>
> On Thu, Jul 31, 2014 at 06:28:04PM -0300, Emilio L?pez wrote:
>> This commit adds SoC bus support on the sunxi platform, and exposes
>> information such as the hardware revision to userspace and other kernel
>> clients during init. A message with this information is also printed to
>> the kernel log to ease future bug triaging.
>>
>> Signed-off-by: Emilio L?pez <[email-masked]>
>> ---
>>   arch/arm/mach-sunxi/Kconfig        |   1 +
>>   arch/arm/mach-sunxi/Makefile       |   2 +-
>>   arch/arm/mach-sunxi/sunxi-soc-id.c | 226 +++++++++++++++++++++++++++++++++++++
>>   arch/arm/mach-sunxi/sunxi-soc-id.h |   6 +
>>   4 files changed, 234 insertions(+), 1 deletion(-)
>>   create mode 100644 arch/arm/mach-sunxi/sunxi-soc-id.c
>>   create mode 100644 arch/arm/mach-sunxi/sunxi-soc-id.h
>>
>> diff --git a/arch/arm/mach-sunxi/Kconfig b/arch/arm/mach-sunxi/Kconfig
>> index 6434e3b..4a199df 100644
>> --- a/arch/arm/mach-sunxi/Kconfig
>> +++ b/arch/arm/mach-sunxi/Kconfig
>> @@ -5,6 +5,7 @@ menuconfig ARCH_SUNXI
>>   	select GENERIC_IRQ_CHIP
>>   	select PINCTRL
>>   	select PINCTRL_SUNXI
>> +	select SOC_BUS
>>   	select SUN4I_TIMER
>>
>>   if ARCH_SUNXI
>> diff --git a/arch/arm/mach-sunxi/Makefile b/arch/arm/mach-sunxi/Makefile
>> index 27b168f..589239b 100644
>> --- a/arch/arm/mach-sunxi/Makefile
>> +++ b/arch/arm/mach-sunxi/Makefile
>> @@ -1,2 +1,2 @@
>> -obj-$(CONFIG_ARCH_SUNXI) += sunxi.o
>> +obj-$(CONFIG_ARCH_SUNXI) += sunxi.o sunxi-soc-id.o
>>   obj-$(CONFIG_SMP) += platsmp.o
>> diff --git a/arch/arm/mach-sunxi/sunxi-soc-id.c b/arch/arm/mach-sunxi/sunxi-soc-id.c
>> new file mode 100644
>> index 0000000..c7eff1c
>> --- /dev/null
>> +++ b/arch/arm/mach-sunxi/sunxi-soc-id.c
>> @@ -0,0 +1,226 @@
>> +/*
>> + * SoC revision detection for sunxi SoCs
>> + *
>> + * Copyright 2014 Emilio L?pez
>> + *
>> + * Emilio L?pez <[email-masked]>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, or
>> + * (at your option) any later version.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/err.h>
>> +#include <linux/io.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/slab.h>
>> +#include <linux/string.h>
>> +#include <linux/sys_soc.h>
>> +
>> +#include "sunxi-soc-id.h"
>> +
>> +/*
>> + * On the A10 SoC, we can read the revision information from the timer
>> + * block. The detection logic is extracted from similar code on the
>> + * Allwinner vendor tree, as this is undocumented on the user manual
>> + */
>> +
>> +#define TIMER_SOC_REV_REG		0x13c
>> +#define TIMER_SOC_REV_CLEAR(val)	((val) & ~(0x3 << 6))
>> +#define TIMER_SOC_REV_GET(val)		(((val) >> 6) & 0x3)
>> +
>> +static const struct of_device_id sun4i_timer_compatible[] __initconst = {
>> +	{ .compatible = "allwinner,sun4i-a10-timer", },
>> +	{},
>> +};
>> +
>> +static int __init sun4i_get_soc_revision(void)
>> +{
>> +	struct device_node *np;
>> +	void __iomem *base;
>> +	u32 val;
>> +	int ret;
>> +
>> +	/* Find the timer node */
>> +	np = of_find_matching_node(NULL, sun4i_timer_compatible);
>> +	if (!np)
>> +		return -ENODEV;
>> +
>> +	/* Temporarily map it for reading */
>> +	base = of_iomap(np, 0);
>> +	if (!base) {
>> +		of_node_put(np);
>> +		return -ENOMEM;
>> +	}
>> +
>> +	/* Clear the SoC revision bits and rewrite the register */
>> +	val = readl(base + TIMER_SOC_REV_REG);
>> +	val = TIMER_SOC_REV_CLEAR(val);
>> +	writel(val, base + TIMER_SOC_REV_REG);
>> +
>> +	/* Now read it again and see what shows up */
>> +	val = readl(base + TIMER_SOC_REV_REG);
>> +	val = TIMER_SOC_REV_GET(val);
>> +
>> +	switch (val) {
>> +	case 0:  /* revision A */
>> +		ret = 'A';
>> +	case 3:  /* revision B */
>> +		ret = 'B';
>> +	default: /* revision C */
>> +		ret = 'C';
>
> What's programmed in there in the case of the rev C?

Something that's not a 3 or a 0 - I don't have any more specifics than 
what the Allwinner code does :(

https://github.com/linux-sunxi/linux-sunxi/blob/lichee-dev/arch/arm/mach-sun4i/core.c#L418

I just noticed that I forgot the breaks while reworking this from return 
to a variable, so everything is rev C right now - I'll fix that.

>> +	}
>> +
>> +	iounmap(base);
>> +	of_node_put(np);
>> +
>> +	return ret;
>> +}
>> +
>> +/*
>> + * On the sun5i SoCs (A10S, A13), we can read the revision information
>> + * from the first bits in the Security ID. The detection logic is
>> + * extracted from similar code on the Allwinner vendor tree, as this
>> + * is undocumented on the user manual.
>> + */
>> +
>> +static const struct of_device_id sun5i_sid_compatible[] __initconst = {
>> +	{ .compatible = "allwinner,sun4i-a10-sid", },
>> +	{},
>> +};
>> +
>> +static int __init sun5i_get_soc_revision(void)
>> +{
>> +	struct device_node *np;
>> +	void __iomem *sid;
>> +	u32 val;
>> +	int ret;
>> +
>> +	/* Find the SID node */
>> +	np = of_find_matching_node(NULL, sun5i_sid_compatible);
>> +	if (!np)
>> +		return -ENODEV;
>> +
>> +	/* Temporarily map it for reading */
>> +	sid = of_iomap(np, 0);
>> +	if (!sid) {
>> +		of_node_put(np);
>> +		return -ENOMEM;
>> +	}
>> +
>> +	/* Read and extract the chip revision from the SID */
>> +	val = readl(sid);
>> +	val = (val >> 8) & 0xffffff;
>> +
>> +	switch (val) {
>> +	case 0:        /* A10S/A13 rev A */
>> +	case 0x162541: /* A10S/A13 rev A */
>> +	case 0x162565: /* A13 rev A */
>
> Some defines would be nice.

Ok

> Also, isn't the SID supposed to identify any SoC, not just the sun5i?

The Allwinner code I've seen uses the SS to detect the SoC (which 
luckily we don't need, as we have DT) and then reads the timer for sun4i 
or the SID for sun5i.

>> +		ret = 'A';
>> +		break;
>> +	case 0x162542: /* A10S/A13 rev B */
>> +		ret = 'B';
>> +		break;
>> +	default:       /* Unknown chip revision */
>> +		ret = -ENODATA;
>> +	}
>> +
>> +	iounmap(sid);
>> +	of_node_put(np);
>> +
>> +	return ret;
>> +}
>> +
>> +int __init sunxi_soc_revision(void)
>> +{
>> +	static int revision = -ENODEV;
>> +
>> +	/* Try to query the hardware just once */
>> +	if (!IS_ERR_VALUE(revision))
>> +		return revision;
>> +
>> +	if (of_machine_is_compatible("allwinner,sun4i-a10")) {
>> +		revision = sun4i_get_soc_revision();
>> +	} else if (of_machine_is_compatible("allwinner,sun5i-a10s") ||
>> +		   of_machine_is_compatible("allwinner,sun5i-a13")) {
>> +		revision = sun5i_get_soc_revision();
>> +	}
>> +
>> +	return revision;
>> +}
>> +
>> +/* Matches for the sunxi SoCs we know of */
>> +static const struct of_device_id soc_matches[] __initconst = {
>> +	{ .compatible = "allwinner,sun4i-a10", .data = "A10 (sun4i)" },
>> +	{ .compatible = "allwinner,sun5i-a13", .data = "A13 (sun5i)" },
>> +	{ .compatible = "allwinner,sun5i-a10s", .data = "A10S (sun5i)" },
>> +	{ .compatible = "allwinner,sun6i-a31", .data = "A31 (sun6i)" },
>> +	{ .compatible = "allwinner,sun7i-a20", .data = "A20 (sun7i)" },
>> +	{ .compatible = "allwinner,sun8i-a23", .data = "A23 (sun8i)" },
>> +	{ /* sentinel */ },
>> +};
>
> Hmmm, no, either auto-detect it, or don't, but that's useless. We can
> already have the same information from the DT directly.

I don't quite get what you're trying to say here. This is here to
a) get a fancy string saying what the SoC is (AFAIK that's not directly 
available on the DT)
b) only run in the listed SoCs

>> +static int __init sunxi_register_soc_device(void)
>> +{
>> +	struct soc_device_attribute *soc_dev_attr;
>> +	struct soc_device *soc_dev;
>> +	const struct of_device_id *match;
>> +	struct device_node *root;
>> +	int revision;
>> +
>> +	/* Only run on sunxi SoCs that we know of */
>> +	root = of_find_node_by_path("/");
>> +	match = of_match_node(soc_matches, root);
>> +	if (!match)
>> +		goto exit;

See here

>> +
>> +	soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
>> +	if (!soc_dev_attr)
>> +		goto exit;
>> +
>> +	/* Read the machine name if available */
>> +	of_property_read_string(root, "model", &soc_dev_attr->machine);
>> +
>> +	soc_dev_attr->family = kstrdup("Allwinner A Series", GFP_KERNEL);
>
> I think the family should be sun*i

Here is a list of the ones currently in use for family

"Cirrus Logic EP93xx"
"Freescale i.MX"
"Integrator"
"Marvell"
"Freescale MXS Family"
"Tegra"
"Xilinx Zynq"

There does not seem to be a real consensus on what these mean. There's a 
binding document on Documentation/ABI/testing/sysfs-devices-soc but it's 
not really detailed.

>
>> +	soc_dev_attr->soc_id = kstrdup(match->data, GFP_KERNEL);
>
> And soc_id would be just the name of the SoC.

According to the binding this is a serial number. Lee, could you help us 
decide what these fields should look like?

I'm now inclining to have eg. family=sun5i, machine=A13, keep revision 
the same and drop soc_id.

>> +
>> +	/* Revision may not always be available */
>> +	revision = sunxi_soc_revision();
>> +	if (IS_ERR_VALUE(revision))
>> +		soc_dev_attr->revision = kstrdup("Unknown", GFP_KERNEL);
>> +	else
>> +		soc_dev_attr->revision = kasprintf(GFP_KERNEL, "%c", revision);
>> +
>> +	soc_dev = soc_device_register(soc_dev_attr);
>> +	if (IS_ERR(soc_dev))
>> +		goto free_struct;
>> +
>> +	/*
>> +	 * Print an informational line mentioning the hardware details.
>> +	 * It may come in handy during bug reports, as some early SoC
>> +	 * revisions have hardware quirks and do not get much testing.
>> +	 */
>> +	pr_info("SoC bus registered, running %s %s, revision %s\n",
>> +		soc_dev_attr->family, soc_dev_attr->soc_id,
>> +		soc_dev_attr->revision);
>
> Maybe a pr_fmt would be nice here.

With something like "Allwinner SoC bus"?

>> +
>> +	return 0;
>> +
>> +free_struct:
>> +	kfree(soc_dev_attr->family);
>> +	kfree(soc_dev_attr->soc_id);
>> +	kfree(soc_dev_attr->revision);
>> +	kfree(soc_dev_attr);
>> +exit:
>> +	of_node_put(root);
>> +
>> +	return 0;
>> +}
>> +postcore_initcall(sunxi_register_soc_device)
>
> I'm kind of reluctant to this. That would mean that it will run for
> every SoC.

The overhead should be negligible - on non-sunxi, it will only check if 
the machine is compatible by looking at the root node and bail out as 
it's not the case.

> Can't you tie it to the system controller, and have it probed as
> usual?

I considered tying this to init_machine, right before the DT starts to 
get probed. That would mean actually writing init_machine hooks calling 
into this for some of our machines, and getting us further from the 
generic DT machine nirvana though. As the quirk bits do not directly 
depend on this, we can probably get away with making this a normal
driver compatible with all our SoCs. Let me know which way do you 
prefer, and I'll be happy to oblige.

Cheers!

Emilio