linux-kernel - [PATCH] phy: Add exynos-phy driver

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Message-id: <1385558788-10880-1-git-send-email-t.stanislaws@samsung.com>
Date:	Wed, 27 Nov 2013 14:26:27 +0100
From:	Tomasz Stanislawski <t.stanislaws@...sung.com>
To:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org
Cc:	t.figa@...sung.com, kgene.kim@...sung.com, grant.likely@...aro.org,
	rob.herring@...xeda.com, sylvester.nawrocki@...il.com,
	kishon@...com, kyungmin.park@...sung.com,
	Tomasz Stanislawski <t.stanislaws@...sung.com>
Subject: [PATCH] phy: Add exynos-phy driver

Hello everyone,
The Samsung SoCs from Exynos family are enhanced with a bunch of switches
dedicated for IP blocks. Those switches are called PHYs in Exynos
specification. They are usually controlled by a single bit in a single
one-word-long register.

A IP driver has to control such a switch in an abstract manner.  Therefore,
such 'enablers' were implemented as clocks in older versions of Linux kernel.
With the dawn of PHY subsystems, PHYs become a natural way of exporting the
'enabler' functionality to drivers.  However, there is an unexpected
consequence. Some of those 1-bit PHYs were implemented as separate drivers.
This means that one has to create a struct device, struct phy, its phy provider
and 100-150 lines of driver code to basically set one bit.

The DP phy driver is a good example:
https://lkml.org/lkml/2013/7/18/53

And simple-phy RFC (shares only driver code but not other resources):
https://lkml.org/lkml/2013/10/21/313

To avoid waste of resources I propose to create all such 1-bit phys from Exynos
SoC using a single device, driver and phy provider.

This patchset contains a proposed solution.

All comment are welcome.

Hopefully in future the functionality introduced by this patch may be merged
into a larger Power Management Unit (PMU) gluer driver.  On Samsusng SoC , the
PMU part contains a number of register barely linked to power management (like
clock gating, clock dividers, CPU resetting, etc.).  It may be tempting to
create a hybrid driver that export clocks/phys/etc that are controlled by PMU
unit.

Regards,
Tomasz Stanislawski

Tomasz Stanislawski (1):
  phy: Add exynos-phy driver

 drivers/phy/Kconfig      |    5 ++
 drivers/phy/Makefile     |    1 +
 drivers/phy/exynos-phy.c |  152 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 158 insertions(+)
 create mode 100644 drivers/phy/exynos-phy.c

-- 
1.7.9.5

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