linux-kernel - Re: [PATCH v3 2/9] soc: samsung: Convert exynos-chipid driver to use the regmap API

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Message-ID: <CAJKOXPf597CMx=M2JmSTWe2GzBfcHFefgzSJbJ+njZGp-WfR1A@mail.gmail.com>
Date:   Tue, 20 Aug 2019 21:37:29 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Jon Hunter <jonathanh@...dia.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc:     robh+dt@...nel.org, vireshk@...nel.org, devicetree@...r.kernel.org,
        kgene@...nel.org, pankaj.dubey@...sung.com,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-pm@...r.kernel.org,
        Bartłomiej Żołnierkiewicz 
        <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v3 2/9] soc: samsung: Convert exynos-chipid driver to use
 the regmap API

On Tue, 20 Aug 2019 at 21:24, Jon Hunter <jonathanh@...dia.com> wrote:
>
>
> On 13/08/2019 16:08, Sylwester Nawrocki wrote:
> > Convert the driver to use regmap API in order to allow other
> > drivers, like ASV, to access the CHIPID registers.
> >
> > This patch adds definition of selected CHIPID register offsets
> > and register bit fields for Exynos5422 SoC.
> >
> > Signed-off-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
> > ---
> > Changes since v2:
> >  - s/_EXYNOS_ASV_H/__LINU_SOC_EXYNOS_ASV_H,
> >  - removed __func__ from error log,
> >  - removed unneeded <linux/of_address.h> header inclusion.
> >
> > Changes since v1 (RFC):
> >  - new patch
> > ---
> >  drivers/soc/samsung/exynos-chipid.c       | 34 ++++++---------
> >  include/linux/soc/samsung/exynos-chipid.h | 52 +++++++++++++++++++++++
> >  2 files changed, 65 insertions(+), 21 deletions(-)
> >  create mode 100644 include/linux/soc/samsung/exynos-chipid.h
> >
> > diff --git a/drivers/soc/samsung/exynos-chipid.c b/drivers/soc/samsung/exynos-chipid.c
> > index bcf691f2b650..006a95feb618 100644
> > --- a/drivers/soc/samsung/exynos-chipid.c
> > +++ b/drivers/soc/samsung/exynos-chipid.c
> > @@ -9,16 +9,13 @@
> >   */
> >
> >  #include <linux/io.h>
> > +#include <linux/mfd/syscon.h>
> >  #include <linux/of.h>
> > -#include <linux/of_address.h>
> > +#include <linux/regmap.h>
> >  #include <linux/slab.h>
> > +#include <linux/soc/samsung/exynos-chipid.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;
> > @@ -51,29 +48,24 @@ static const char * __init product_id_to_soc_id(unsigned int product_id)
> >  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;
> > +     struct regmap *regmap;
> >       u32 product_id;
> >       u32 revision;
> > +     int ret;
> >
> > -     /* 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;
> > +     regmap = syscon_regmap_lookup_by_compatible("samsung,exynos4210-chipid");
> > +     if (IS_ERR(regmap)) {
> > +             pr_err("Failed to get CHIPID regmap\n");
> > +             return PTR_ERR(regmap);
> >       }
>
> Following this change, I am now seeing the above error on our Tegra
> boards where this driver is enabled. This is triggering a kernel
> warnings test we have to fail. Hence, I don't think that you can remove
> the compatible node test here, unless you have a better way to determine
> if this is a samsung device.

Right, this is really wrong... I missed that it is not a probe but
early init. And this init will be called on every board... Probably it
should be converted to a regular driver.

This is very old patchset, revived recently. I see that in v6 it was a
platform driver:
https://patchwork.kernel.org/patch/9134949/
Pankaj, apparently based on these comments, made it initcall... but why?

Another point is that Arnd complained there about exposing global
header and no change here - we still expose the global header, but not
with soc revisions but register internals... although it has its
purpose - other Exynos-specific drivers need to access through regmap.

Best regards,
Krzysztof