linux-kernel - Re: [PATCH v5] mfd: syscon: Decouple syscon interface from platform devices

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Date:	Tue, 23 Sep 2014 20:12:50 +0200
From:	Joachim Eastwood <manabian@...il.com>
To:	Pankaj Dubey <pankaj.dubey@...sung.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-samsung-soc@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kgene.kim@...sung.com,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, naushad@...sung.com,
	b29396@...escale.com, tomasz.figa@...il.com, joshi@...sung.com,
	thomas.ab@...sung.com, Li.Xiubo@...escale.com,
	vikas.sajjan@...sung.com, chow.kim@...sung.com,
	lee.jones@...aro.org
Subject: Re: [PATCH v5] mfd: syscon: Decouple syscon interface from platform devices

On 22 September 2014 06:40, Pankaj Dubey <pankaj.dubey@...sung.com> wrote:
> Currently a syscon entity can be only registered directly through a
> platform device that binds to a dedicated syscon driver. However in
> certain use cases it is desirable to make a device used with another
> driver a syscon interface provider.
>
> 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.
>
> In case of DT based platforms, 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 keep
> a list of such syscon objects along with syscon provider device_nodes
> and regmap handles.
>
> For non-DT based platforms, this patch keeps syscon platform driver
> structure where is can be probed and such non-DT based drivers can use
> syscon_regmap_lookup_by_pdev API and get access to regmap handles.
> Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> we can completly remove platform driver of syscon, and keep only helper
> functions to get regmap handles.
>
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Suggested-by: Tomasz Figa <tomasz.figa@...il.com>
> Tested-by: Vivek Gautam <gautam.vivek@...sung.com>
> Tested-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>

Hi Pankaj,

I wrote a clk driver using syscon and your patch. clk driver uses
CLK_OF_DECLARE, btw.

It works but I get a '(null): Failed to create debugfs directory'
message in the boot log.

Tested-by: Joachim Eastwood <manabian@...il.com>

regards,
Joachim Eastwood
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