[PATCH v3] spi: rockchip: initialize bus_num to -1

[Stephano Cetola <stephano@cetola.net>]

spi_register_controller() only runs the OF alias lookup when
ctrl->bus_num is negative. This driver's kzalloc'd ctlr leaves
bus_num at 0. The lookup gets skipped. Every Rockchip SPI controller
ends up on bus 0.

Any board that enables two Rockchip SPI controllers at once hits this
bug. Both end up on bus 0. Looking one up by bus number can then
return the wrong controller.

Use -1 here to trigger the lookup from the device tree. No board board
file deliberately sets the id.

Fixes: 1efba64ba04 ("spi: add rockchip spi controller support")
Signed-off-by: Stephano Cetola <stephano@cetola.net>
---
We saw this on the MNT Pocket Reform (RK3588S). spi@feb20000 returns
the PMIC controller instead of the intended gpio-spi RP2040 bus. The
barebox spi command then does a write+read through the Rockchip SPI
driver, which programmes the hardware in XFM_RO (RX-only) mode for
the read phase. In that mode dummy TXDR writes don't generate clock
pulses, the RX FIFO never fills, and rockchip_spi_pio's while(1) loop
never exits.
---
Changes in v3:
- Initialize bus_num to -1 directly. Copying dev->id worked by
  coincidence, not by design.
- Rewrote the commit message to explain why -1 is correct, per
  Sascha's review.
- Link to v2: https://patch.msgid.link/20260822-send-spi-rockchip-busnum-v2-1-0f43376cb391@cetola.net

Changes in v2:
- Updated commit message for clarity.
- Link to v1: https://patch.msgid.link/20260822-send-spi-rockchip-busnum-v1-1-bf9c183786e4@cetola.net

To: Sascha Hauer <s.hauer@pengutronix.de>
To: "open list:BAREBOX" <barebox@lists.infradead.org>
---
 drivers/spi/spi-rockchip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 1e81e9393f..0ee31c1f55 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -514,7 +514,7 @@ static int rockchip_spi_probe(struct device *dev)
 		goto err_put_ctlr;
 	}
 
-//	ctlr->bus_num = pdev->id;
+	ctlr->bus_num = -1;
 //	ctlr->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP | SPI_LSB_FIRST;
 
 	/*

---
base-commit: 9bc1a26592a59919d2ee8c60c273d87d3d9f2e81
change-id: 20260821-send-spi-rockchip-busnum-a9b1116e14a5