[RFC PATCH 0/1] phy: mediatek: phy-mtk-hdmi: Use regmap to manipulate hdmi registers

[Luca Leonardo Scorcia <l.scorcia@gmail.com>]

While working on MediaTek mt8167 HDMI support I noticed that on some SoCs
like mt8167 and mt8173 the registers used by HDMI PHY are actually inside
the memory space mapped by the apmixedsys driver. On mt8173 this driver
maps its memory using of_iomap, while on mt8167 it currently uses
devm_platform_ioremap_resource. The current phy_hdmi_mtk uses
devm_platform_ioremap_resource too, which causes a conflict between the
two at probe:

hdmi-phy: error -EBUSY: can't request region for resource
[mem 0x10018300-0x1001831f]

In patch [1] I initially proposed to use the same approach of mt8173
in mt8167 too. While working Sashiko correctly pointed out that it never
unmaps its memory during remove [2], even on mt8173. It is of course
possible to add code for that, but it would mean creating a dedicated
drvdata structure, and it seems a little invasive. Using the devm_*
functions is certainly cleaner.

This patch goes in the opposite direction - it converts all register
access for mtk hdmi phy to the regmap_* functions and obtains the regmap
using device_node_to_regmap, which internally uses iomap and does not
trigger the conflict. This way memory can still be managed by the
apmixedsys driver using the devm_* and the HDMI phy only gets a regmap.

This patch has been tested on mt8167 only. Unfortunately I have no devices
with the other SoCs that are touched by this refactoring, so I am sending
it as a RFC to gather feedback from more experienced kernel devs.

[1] https://lore.kernel.org/linux-mediatek/20261010115539.9237-4-l.scorcia@gmail.com/T/#u
[2] https://sashiko.dev/#/patchset/20261010115539.9237-1-l.scorcia%40gmail.com

Luca Leonardo Scorcia (1):
  phy: mediatek: phy-mtk-hdmi: Use regmap to manipulate hdmi registers

 drivers/phy/mediatek/phy-mtk-hdmi-mt2701.c | 145 ++++++++--------
 drivers/phy/mediatek/phy-mtk-hdmi-mt8173.c | 133 +++++++--------
 drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c | 185 ++++++++++-----------
 drivers/phy/mediatek/phy-mtk-hdmi.c        |   2 +-
 drivers/phy/mediatek/phy-mtk-hdmi.h        |   3 +-
 5 files changed, 235 insertions(+), 233 deletions(-)

-- 
2.43.0