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

From: Krzysztof Kozlowski <krzk@kernel.org>
To: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Sylwester Nawrocki <snawrocki@kernel.org>,
	Jon Hunter <jonathanh@nvidia.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-kernel@vger.kernel.org>,
	linux-pm@vger.kernel.org,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	linux-tegra <linux-tegra@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v3 2/9] soc: samsung: Convert exynos-chipid driver to use the regmap API
Date: Wed, 21 Aug 2019 15:10:53 +0200	[thread overview]
Message-ID: <CAJKOXPdbPg-O6zh6LXrvSRSMG8psxW6_eREe+UEH=UZNhAT=rQ@mail.gmail.com> (raw)
In-Reply-To: <537999b7-b0e8-33a7-4bdc-c6952a0a5d06@samsung.com>

On Wed, 21 Aug 2019 at 14:41, Sylwester Nawrocki <s.nawrocki@samsung.com> wrote:
>
> On 8/21/19 14:16, Krzysztof Kozlowski wrote:
> >>> I'm also inclined to have it converted to a regular driver.  We already
> >>> have "exynos-asv" driver matching on the chipid node (patch 3/9).
> >>> The ASV patches will not be merged soon anyway, all this needs some more
> >>> thought. Krzysztof, can we abandon the chipid patches for now? Your
> >>
> >> chipid driver is good and useful on its own. The preferred solution
> >> IMHO would be to just revert "soc: samsung: Convert exynos-chipid
> >> driver to use the regmap API" commit.
> >
> > I queued the chipid as a dependency for ASV but ASV requires the
> > regmap. What would be left after reverting the regmap part? Simple
> > unused printk driver? No need for such. If reverting, then let's drop
> > entire driver and rework it offline.
>
> In fact there is now no dependency between the chipid and the ASV
> driver (patch 3/9), the regmap is provided by the syscon driver/API.
> I should have added "depends on REGMAP && MFD_SYSCON" to Kconfig.
> Both drivers (chipid, ASV) share the registers region so the regmap
> API seemed appropriate here.

Indeed, ASV needs only the header + DT change... Then actually we do
not need chipid driver at all. Just to print the SoC and provide sysfs
entry? If this is the only purpose, then it should be a driver.

> Converting the chipid code to platform driver wouldn't make sense as
> it wouldn't be useful early in arch/arm/mach-exynos and we can't have
> two drivers for same device (the ASV driver matches on the chipid
> compatible now).

There is no use case for arm/mach-exynos. This code was not
resubmitted and I doubt it will be (unless now someone wants to prove
I am wrong and sends it again :) ). The two-device case is indeed a
problem but it is possible. Clocks are doing it with PMU driver. See
CLK_OF_DECLARE_DRIVER(), although I do not remember whether it is
maybe obsolete pattern (discouraged).

Best regards,
Krzysztof