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The Exynos Chip ID driver on Exynos SoCs has so far only informational
purpose - to expose the SoC device in sysfs. No other drivers depend on
it so there is really no benefit of initializing it early.
The code would be the most flexible if converted to a regular driver.
However there is already another driver - Exynos ASV (Adaptive Supply
Voltage) - which binds to the device node of Chip ID.
The solution is to convert the Exynos Chip ID to a built in driver and
merge the Exynos ASV into it.
This has several benefits:
1. Although the Exynos ASV driver binds to a device node present in all
Exynos DTS (generic compatible), it fails to probe except on the
supported ones (only Exynos5422). This means that the regular boot
process has a planned/normal device probe failure.
Merging the ASV into Chip ID will remove this probe failure because
the final driver will always bind, just with disabled ASV features.
2. Allows to use dev_info() as the SoC bus is present (since
core_initcall).
3. Could speed things up because of execution of Chip ID code in a SMP
environment (after bringing up secondary CPUs, unlike early_initcall),
This reduces the amount of work to be done early, when the kernel has
to bring up critical devices.
5. Makes the Chip ID code defer-probe friendly,
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201207190517.262051-5-krzk@kernel.org
Reviewed-by: Pankaj Dubey <pankaj.dubey@samsung.com>
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The Adaptive Supply Voltage (ASV) driver adjusts CPU cluster operating
points depending on exact revision of an SoC retrieved from the CHIPID
block or the OTP memory. This allows for some power saving as for some
CPU clock frequencies we can lower CPU cluster's supply voltage comparing
to safe values common to all the SoC revisions.
This patch adds support for Exynos5422/5800 SoC, it is partially based
on code from https://github.com/hardkernel/linux repository,
branch odroidxu4-4.14.y, files: arch/arm/mach-exynos/exynos5422-asv.[ch].
Tested on Odroid XU3, XU4, XU3 Lite.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
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