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Subject: Re: [PATCH v2 1/9] soc: samsung: Add exynos chipid driver support
To:     Krzysztof Kozlowski <krzk@kernel.org>
Cc:     Sylwester Nawrocki <s.nawrocki@samsung.com>, robh+dt@kernel.org,
        vireshk@kernel.org, devicetree@vger.kernel.org, kgene@kernel.org,
        pankaj.dubey@samsung.com,
        "linux-samsung-soc@vger.kernel.org" 
        <linux-samsung-soc@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org,
        Marek Szyprowski <m.szyprowski@samsung.com>
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Message-ID: <1117f432-8adf-fbe9-f4af-f8acb755326e@samsung.com>
Date:   Tue, 23 Jul 2019 16:10:05 +0200
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Hi Krzysztof,

On 7/23/19 2:57 PM, Krzysztof Kozlowski wrote:
> On Thu, 18 Jul 2019 at 16:31, Sylwester Nawrocki <s.nawrocki@samsung.com> wrote:
>>
>> From: Pankaj Dubey <pankaj.dubey@samsung.com>
>>
>> Exynos SoCs have Chipid, for identification of product IDs and SoC
>> revisions. This patch intends to provide initialization code for all
>> these functionalities, at the same time it provides some sysfs entries
>> for accessing these information to user-space.
>>
>> This driver uses existing binding for exynos-chipid.
>>
>> Changes by Bartlomiej:
>> - fixed return values on errors
>> - removed bogus kfree_const()
>> - added missing Exynos4210 EVT0 id
>> - converted code to use EXYNOS_MASK define
>> - fixed np use after of_node_put()
>> - fixed too early use of dev_info()
>> - made driver fail for unknown SoC-s
>> - added SPDX tag
>> - updated Copyrights
>>
>> Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
>> [m.szyprowski: for suggestion and code snippet of product_id_to_soc_id]
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
>> [s.nawrocki: updated copyright date]
>> Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
>> ---
>>  drivers/soc/samsung/Kconfig         |   5 ++
>>  drivers/soc/samsung/Makefile        |   2 +
>>  drivers/soc/samsung/exynos-chipid.c | 111 ++++++++++++++++++++++++++++
>>  3 files changed, 118 insertions(+)
>>  create mode 100644 drivers/soc/samsung/exynos-chipid.c
>>
>> diff --git a/drivers/soc/samsung/Kconfig b/drivers/soc/samsung/Kconfig
>> index 2186285fda92..2905f5262197 100644
>> --- a/drivers/soc/samsung/Kconfig
>> +++ b/drivers/soc/samsung/Kconfig
>> @@ -7,6 +7,11 @@ menuconfig SOC_SAMSUNG
>>
>>  if SOC_SAMSUNG
>>
>> +config EXYNOS_CHIPID
>> +       bool "Exynos Chipid controller driver" if COMPILE_TEST
>> +       depends on ARCH_EXYNOS || COMPILE_TEST
>> +       select SOC_BUS
>> +
>>  config EXYNOS_PMU
>>         bool "Exynos PMU controller driver" if COMPILE_TEST
>>         depends on ARCH_EXYNOS || ((ARM || ARM64) && COMPILE_TEST)
>> diff --git a/drivers/soc/samsung/Makefile b/drivers/soc/samsung/Makefile
>> index 29f294baac6e..3b6a8797416c 100644
>> --- a/drivers/soc/samsung/Makefile
>> +++ b/drivers/soc/samsung/Makefile
>> @@ -1,4 +1,6 @@
>>  # SPDX-License-Identifier: GPL-2.0
>> +
>> +obj-$(CONFIG_EXYNOS_CHIPID)    += exynos-chipid.o
>>  obj-$(CONFIG_EXYNOS_PMU)       += exynos-pmu.o
>>
>>  obj-$(CONFIG_EXYNOS_PMU_ARM_DRIVERS)   += exynos3250-pmu.o exynos4-pmu.o \
>> diff --git a/drivers/soc/samsung/exynos-chipid.c b/drivers/soc/samsung/exynos-chipid.c
>> new file mode 100644
>> index 000000000000..78b123ee60c0
>> --- /dev/null
>> +++ b/drivers/soc/samsung/exynos-chipid.c
>> @@ -0,0 +1,111 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2019 Samsung Electronics Co., Ltd.
>> + *           http://www.samsung.com/
>> + *
>> + * EXYNOS - CHIP ID support
>> + * Author: Pankaj Dubey <pankaj.dubey@samsung.com>
>> + * Author: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
>> + */
>> +
>> +#include <linux/io.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/platform_device.h>
> 
> Any changes here from my previous comments?
> 
> I have also one more new thought later.
> 
>> +#include <linux/slab.h>
>> +#include <linux/sys_soc.h>
>> +
>> +#define EXYNOS_SUBREV_MASK     (0xF << 4)
>> +#define EXYNOS_MAINREV_MASK    (0xF << 0)
>> +#define EXYNOS_REV_MASK                (EXYNOS_SUBREV_MASK | EXYNOS_MAINREV_MASK)
>> +#define EXYNOS_MASK            0xFFFFF000
>> +
>> +static const struct exynos_soc_id {
>> +       const char *name;
>> +       unsigned int id;
>> +} soc_ids[] = {
>> +       { "EXYNOS3250", 0xE3472000 },
>> +       { "EXYNOS4210", 0x43200000 },   /* EVT0 revision */
>> +       { "EXYNOS4210", 0x43210000 },
>> +       { "EXYNOS4212", 0x43220000 },
>> +       { "EXYNOS4412", 0xE4412000 },
>> +       { "EXYNOS5250", 0x43520000 },
>> +       { "EXYNOS5260", 0xE5260000 },
>> +       { "EXYNOS5410", 0xE5410000 },
>> +       { "EXYNOS5420", 0xE5420000 },
>> +       { "EXYNOS5440", 0xE5440000 },
>> +       { "EXYNOS5800", 0xE5422000 },
>> +       { "EXYNOS7420", 0xE7420000 },
>> +       { "EXYNOS5433", 0xE5433000 },
>> +};
>> +
>> +static const char * __init product_id_to_soc_id(unsigned int product_id)
>> +{
>> +       int i;
>> +
>> +       for (i = 0; i < ARRAY_SIZE(soc_ids); i++)
>> +               if ((product_id & EXYNOS_MASK) == soc_ids[i].id)
>> +                       return soc_ids[i].name;
>> +       return NULL;
>> +}
>> +
>> +int __init exynos_chipid_early_init(void)
>> +{
>> +       struct soc_device_attribute *soc_dev_attr;
>> +       void __iomem *exynos_chipid_base;
>> +       struct soc_device *soc_dev;
>> +       struct device_node *root;
>> +       struct device_node *np;
>> +       u32 product_id;
>> +       u32 revision;
>> +
>> +       /* look up for chipid node */
>> +       np = of_find_compatible_node(NULL, NULL, "samsung,exynos4210-chipid");
>> +       if (!np)
>> +               return -ENODEV;
>> +
>> +       exynos_chipid_base = of_iomap(np, 0);
>> +       of_node_put(np);
>> +
>> +       if (!exynos_chipid_base) {
>> +               pr_err("Failed to map SoC chipid\n");
>> +               return -ENXIO;
>> +       }
>> +
>> +       product_id = readl_relaxed(exynos_chipid_base);
>> +       revision = product_id & EXYNOS_REV_MASK;
>> +       iounmap(exynos_chipid_base);
>> +
>> +       soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
>> +       if (!soc_dev_attr)
>> +               return -ENOMEM;
>> +
>> +       soc_dev_attr->family = "Samsung Exynos";
>> +
>> +       root = of_find_node_by_path("/");
>> +       of_property_read_string(root, "model", &soc_dev_attr->machine);
>> +       of_node_put(root);
>> +
>> +       soc_dev_attr->revision = kasprintf(GFP_KERNEL, "%x", revision);
>> +       soc_dev_attr->soc_id = product_id_to_soc_id(product_id);
>> +       if (!soc_dev_attr->soc_id) {
>> +               pr_err("Unknown SoC\n");
> 
> In case of running old kernel on unknown SoC (new revision of existing
> one or older design not longer supported like 4415), the device will
> not bind. This was added by Bartlomiej. Why? I imagine that soc driver
> could be still matched and just report "Unknown". I am not sure if
> this changes anything, though.

I was thinking that we shouldn't be pretending that we know how to
handle unsupported SoCs, i.e. that we know how to correctly read its
product_id and revision.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

> Best regards,
> Krzysztof
> 
> 
>> +               return -ENODEV;
>> +       }
>> +
>> +       /* please note that the actual registration will be deferred */
>> +       soc_dev = soc_device_register(soc_dev_attr);
>> +       if (IS_ERR(soc_dev)) {
>> +               kfree(soc_dev_attr->revision);
>> +               kfree(soc_dev_attr);
>> +               return PTR_ERR(soc_dev);
>> +       }
>> +
>> +       /* it is too early to use dev_info() here (soc_dev is NULL) */
>> +       pr_info("soc soc0: Exynos: CPU[%s] PRO_ID[0x%x] REV[0x%x] Detected\n",
>> +               soc_dev_attr->soc_id, product_id, revision);
>> +
>> +       return 0;
>> +}
>> +early_initcall(exynos_chipid_early_init);
>> --
>> 2.17.1