From: Rahul Sharma Rahul.Sharma@samsung.com
Hi All,
This series has been originally proposed by Tomasz Stanislawski. With his permission, I have addressed the following review comments in V3.
Changelog: v3: * Implement lazy-init of PHYs. * Use MACROs instead of numbers to represent phys. * Use regmap interface to access PMU registers.
It is based on "Next" branch in Kishon Vijay Abraham's tree at https://git.kernel.org/cgit/linux/kernel/git/kishon/linux-phy.git/
/* Original Message from Tomasz Stanislawski t.stanislaws@samsung.com */
The Samsung SoCs from Exynos family are enhanced with a bunch of devices that provide functionality of a physical layer for interfaces like USB, HDMI, SATA, etc. They are controlled by a simple interface, often a single bit that enables and/or resets the physical layer.
An IP driver should to control such a controller 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.
Alternative solutions might be: * exporting a regmap to the IP driver and allow the driver to control the PHY layer like in the patch: http://thread.gmane.org/gmane.linux.kernel.samsung-soc/28617/focus=28648
* create a dedicated power domain for hdmiphy
Regards, Tomasz Stanislawski
v2: * rename to exynos-simple-phy * fix usage of devm_ioremap() * add documentation for DT bindings * add patches to client drivers
v1: initial version
Tomasz Stanislawski (3): phy: Add exynos-simple-phy driver drm: exynos: hdmi: use hdmiphy as PHY s5p-tv: hdmi: use hdmiphy as PHY
.../devicetree/bindings/phy/samsung-phy.txt | 56 ++++++ drivers/gpu/drm/exynos/exynos_hdmi.c | 11 +- drivers/media/platform/s5p-tv/hdmi_drv.c | 11 +- drivers/phy/Kconfig | 5 + drivers/phy/Makefile | 1 + drivers/phy/exynos-simple-phy.c | 189 ++++++++++++++++++++ include/dt-bindings/phy/exynos-simple-phy.h | 27 +++ 7 files changed, 290 insertions(+), 10 deletions(-) create mode 100644 drivers/phy/exynos-simple-phy.c create mode 100644 include/dt-bindings/phy/exynos-simple-phy.h