[PATCH AUTOSEL 6.17-6.1] spi: rpc-if: Add resume support for RZ/G3E

[Sasha Levin <sashal@kernel.org>]

From: Biju Das <biju.das.jz@bp.renesas.com>

[ Upstream commit ad4728740bd68d74365a43acc25a65339a9b2173 ]

On RZ/G3E using PSCI, s2ram powers down the SoC. After resume,
reinitialize the hardware for SPI operations.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patch.msgid.link/20250921112649.104516-3-biju.das.jz@bp.renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

YES

- What changed: The resume callback now reinitializes the underlying
  RPC-IF hardware by calling `rpcif_hw_init(dev, false)` before resuming
  the SPI controller queue. See drivers/spi/spi-rpc-if.c:210. The rest
  of the resume path remains unchanged and returns
  `spi_controller_resume(ctlr)` (drivers/spi/spi-rpc-if.c:212). The
  patch is a small, contained 2-line addition in a single driver file.

- Why it’s needed: On RZ/G3E systems using PSCI, s2ram powers the SoC
  off, so the RPC-IF/xSPI controller loses register state. The SPI
  core’s `spi_controller_resume()` does not reconfigure hardware
  (drivers/spi/spi.c:3519), it only restarts the message queue. Without
  reinitialization, resumed SPI operations can fail or misbehave. The
  added `rpcif_hw_init()` reprograms controller registers and ensures
  the hardware is ready post-resume.

- Correctness of the reinit: `rpcif_hw_init()` is the standard hardware
  bring-up routine used in probe; it resumes runtime PM, reconfigures
  the controller for the appropriate mode, and then drops the PM
  reference. See drivers/memory/renesas-rpc-if.c:315. It’s already
  invoked during probe for the SPI path (drivers/spi/spi-rpc-if.c:173),
  so reusing it on resume is appropriate and consistent.

- Scope and risk: The change is isolated to RPC-IF SPI driver resume. It
  does not alter normal operation, only system-suspend resume behavior.
  The call is idempotent and guarded by runtime PM
  (pm_runtime_resume_and_get/put inside rpcif_hw_init), minimizing risk.
  It doesn’t introduce features or architectural changes.

- Impacted platforms: Although the commit message highlights RZ/G3E
  (xSPI), the reinit is generally safe for other RPC-IF variants too and
  can only improve robustness after system suspend.

- Stable-tree suitability:
  - Fixes a real user-visible bug (SPI transactions can fail after S2RAM
    on RZ/G3E).
  - Minimal change (two added lines), fully contained in the driver.
  - Low regression risk and no API or architectural churn.
  - Touches a specific subsystem driver (SPI/Renesas RPC-IF), not core
    kernel paths.

- Backport notes (API/context):
  - `rpcif_hw_init()` currently takes a `struct device *`
    (drivers/memory/renesas-rpc-if.c:315; include/memory/renesas-rpc-
    if.h:75). On older stable trees that predate commit a198fcd1d53cb
    (which changed RPC-IF APIs to pass a device instead of an internal
    handle), the signature may differ. In such trees, adapt the call
    accordingly (e.g., pass `rpc->dev` or the older handle type).
  - Ensure the device passed to `rpcif_hw_init()` is the one holding
    `rpcif_priv` (in probe we pass `rpc->dev`, which is the parent RPC-
    IF device). If the stable branch still uses the older arrangement,
    the backport should call `rpcif_hw_init(rpc->dev, false)` after
    obtaining `struct rpcif *rpc = spi_controller_get_devdata(ctlr)` in
    resume.
  - Macro context (SIMPLE_DEV_PM_OPS vs DEFINE_SIMPLE_DEV_PM_OPS) may
    differ between branches; this is mechanical and does not affect the
    substance of the fix.

In summary, this is a classic, low-risk, correctness fix for resume on
RZ/G3E that should be backported to stable kernels that include the RPC-
IF xSPI support, with trivial API/context adjustments as needed.

 drivers/spi/spi-rpc-if.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/spi/spi-rpc-if.c b/drivers/spi/spi-rpc-if.c
index 627cffea5d5c7..300a7c10b3d40 100644
--- a/drivers/spi/spi-rpc-if.c
+++ b/drivers/spi/spi-rpc-if.c
@@ -207,6 +207,8 @@ static int __maybe_unused rpcif_spi_resume(struct device *dev)
 {
 	struct spi_controller *ctlr = dev_get_drvdata(dev);
 
+	rpcif_hw_init(dev, false);
+
 	return spi_controller_resume(ctlr);
 }
 
-- 
2.51.0