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SubjectRe: [PATCH v2] mfd: syscon: Decouple syscon interface from platform devices
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On Tuesday 02 September 2014 20:12:15 Pankaj Dubey wrote:
> Currently a syscon entity can only be registered directly through a
> platform device that binds to a dedicated syscon driver. However in
> certain cases it is required to bind a device with it's dedicated
> driver rather than binding with syscon driver.
>
> For example, certain SoCs (e.g. Exynos) contain system controller
> blocks which perform various functions such as power domain control,
> CPU power management, low power mode control, but in addition contain
> certain IP integration glue, such as various signal masks,
> coprocessor power control, etc. In such case, there is a need to have
> a dedicated driver for such system controller but also share registers
> with other drivers. The latter is where the syscon interface is helpful.
>
> This patch decouples syscon object from syscon platform driver, and
> allows to create syscon objects first time when it is required by
> calling of syscon_regmap_lookup_by APIs and keeps a list of such syscon
> objects along with syscon provider device_nodes and regmap handles.
>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> Signed-off-by: Tomasz Figa <t.figa@samsung.com>
> ---
> V1 of this patchset [1] and related discussion can be found here [1].
>
> Changes since v1:
> - Removed of_syscon_unregister function.
> - Modified of_syscon_register function and it will be used by syscon.c
> to create syscon objects whenever required.
> - Removed platform device support from syscon.
> - Removed syscon_regmap_lookup_by_pdevname API support.
> - As there are significant changes w.r.t patchset v1, I am taking over
> author for this patchset from Tomasz Figa.

Note that you got the Signed-off-by: list wrong, you should never have
any people listed as Signed-off-by after your own name, and they should
be listed before your name only when you are forwarding their patches.

> Note: Current kernel has clps711x user of syscon_regmap_lookup_by_pdevname and
> will be broken after this patch. As per discussion over here [1], patches
> for making these drivers DT based are ready and once that is done they can use
> syscon_regmap_lookup_by_phandle or syscon_regmap_lookup_by_compatible.
>
> [1]: https://lkml.org/lkml/2014/8/22/81

Adding Alexander Shiyan to Cc here, so we can make sure this is well
coordinated.

I'm also adding Michal Simek, since here was involved in earlier discussions
about doing this.

> drivers/mfd/syscon.c | 143 +++++++++++++-------------------------------
> include/linux/mfd/syscon.h | 1 +
> 2 files changed, 44 insertions(+), 100 deletions(-)

I certainly like the diffstat ;-)

> struct syscon {
> + struct device_node *np;
> struct regmap *regmap;
> + struct list_head list;
> };

Right

> @@ -68,27 +72,6 @@ struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
> }
> EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);
>
> -static int syscon_match_pdevname(struct device *dev, void *data)
> -{
> - return !strcmp(dev_name(dev), (const char *)data);
> -}
> -
> -struct regmap *syscon_regmap_lookup_by_pdevname(const char *s)
> -{
> - struct device *dev;
> - struct syscon *syscon;
> -
> - dev = driver_find_device(&syscon_driver.driver, NULL, (void *)s,
> - syscon_match_pdevname);
> - if (!dev)
> - return ERR_PTR(-EPROBE_DEFER);
> -
> - syscon = dev_get_drvdata(dev);
> -
> - return syscon->regmap;
> -}
> -EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_pdevname);

I think this can actually be left intact if that helps with clps71xx.
It could be done in a hacky way using bus_find_device_by_name()
to keep it simple, or in a somewhat nicer way by keeping the
syscon platform_driver around for the non-DT case.


> + regmap = regmap_init_mmio(NULL, base, &syscon_regmap_config);
> + if (IS_ERR(regmap)) {
> + pr_err("regmap init failed\n");
> + return ERR_CAST(regmap);
> + }

The last time I looked over this code, I think it was not safe to
call regmap_init_mmio() with a NULL device pointer, and we decided
that should be fixed. Have you checked whether it is ok now?

Arnd


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