[PATCH v6 0/7] mmc: host: renesas_sdhi_core: support configuring an optional sdio mux

Josua Mayer
2026-01-21T09:21:05Z

Some Renesas SoC based boards mux SD and eMMC on a single sdio
controller, exposing user control by dip switch and software control by
gpio.

Purpose is to simplify development and provisioning by selecting boot
media at power-on, and again before starting linux.

Add binding and driver support for linking a (gpio) mux to renesas sdio
controller.

Introduce generic helper functions for getting managed and selected
mux-state objects, and switch i2c-omap and phy-can-transceiver drivers.

Signed-off-by: Josua Mayer <josua@solid-run.com>
---
Changes in v6:
- replaced /* with /** for devm_mux_state_state function description.
- collected review tags.
- fixed checkpatch warnings (space-before-tab, void-return).
(Reported-by: Geert Uytterhoeven)
- fixed use-after-free in mux core mux_get function.
(Reported-by: Geert Uytterhoeven)
- fix mux helper error path uninitialised return code variable.
(Reported-by: kernel test robot <lkp@intel.com>)
- Link to v5: https://lore.kernel.org/r/20260118-rz-sdio-mux-v5-0-3c37e8872683@solid-run.com

Changes in v5:
- implemented automatic mux deselect for devm_*_selected.
(Reported-by: Wolfram Sang <wsa+renesas@sang-engineering.com>)
- because of semantic changes I dropped reviewed and acks from omap-i2c
patch (Andreas Kemnade / Wolfram Sang).
- fix invalid return value in void function for mux helper stubs
(Reported-by: kernel test robot <lkp@intel.com>)
- Link to v4: https://lore.kernel.org/r/20251229-rz-sdio-mux-v4-0-a023e55758fe@solid-run.com

Changes in v4:
- added MULTIPLEXER Kconfig help text.
- removed "select MULTIPLEXER" from renesas sdhi Kconfig, as it is
not required for all devices using this driver.
- added stubs for all symbols exported by mux core.
(Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
- refactored mux core logic to silence ENOENT errors only on optional
code paths, keeping error printing unchanged otherwise.
(Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>)
- picked up various reviewed- and acked-by tags
- Link to v3: https://lore.kernel.org/r/20251210-rz-sdio-mux-v3-0-ca628db56d60@solid-run.com

Changes in v3:
- updated omap-i2c and phy-can-transceiver to use new helpers.
- created generic helper functions for getting managed optional mux-state.
(Reported-by: Rob Herring <robh@kernel.org>)
- picked up binding ack by Rob Herring.
- replaced use of "SDIO" with "SD/SDIO/eMMC" in binding document and
commit descriptions.
(Reported-by: Ulf Hansson <ulf.hansson@linaro.org>)
- Link to v2: https://lore.kernel.org/r/20251201-rz-sdio-mux-v2-0-bcb581b88dd7@solid-run.com

Changes in v2:
- dropped mux-controller node from dt binding example
(Reported-by: Conor Dooley <conor@kernel.org>
Reported-by: Krzysztof Kozlowski <krzk@kernel.org>)
- Link to v1: https://lore.kernel.org/r/20251128-rz-sdio-mux-v1-0-1ede318d160f@solid-run.com

---
Josua Mayer (7):
phy: can-transceiver: rename temporary helper function to avoid conflict
mux: Add helper functions for getting optional and selected mux-state
mux: add help text for MULTIPLEXER config option
phy: can-transceiver: drop temporary helper getting optional mux-state
i2c: omap: switch to new generic helper for getting selected mux-state
dt-bindings: mmc: renesas,sdhi: Add mux-states property
mmc: host: renesas_sdhi_core: support selecting an optional mux

.../devicetree/bindings/mmc/renesas,sdhi.yaml | 6 +
drivers/i2c/busses/i2c-omap.c | 24 +--
drivers/mmc/host/renesas_sdhi_core.c | 6 +
drivers/mux/Kconfig | 8 +
drivers/mux/core.c | 178 +++++++++++++++++----
drivers/phy/phy-can-transceiver.c | 10 --
include/linux/mux/consumer.h | 108 ++++++++++++-
7 files changed, 278 insertions(+), 62 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20251128-rz-sdio-mux-acc5137f1618

Best regards,
--
Josua Mayer <josua@solid-run.com>