board: rockchip: unblock CAN bus in spl_board_init on Jaguar

GPIO0_B7 is routed to TXI of the on-board CAN transceiver. The
line has a pull-down per SoC default.

This means the CAN transceiver transmits a dominant zero
and blocks the CAN bus until Linux boots and reconfigures the pin.

Let's switch to pull-up as soon as we can (i.e. in SPL).
This cuts down the "bus is blocked" time from 10 seconds to < 1 second.

Of course, to this needs CONFIG_SPL_BOARD_INIT, so enable it
the Jaguar defconfig.

Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>

board/theobroma-systems/jaguar_rk3588/jaguar_rk3588.c

@@ -51,3 +51,22 @@ int rockchip_early_misc_init_r(void)
 
 	return 0;
 }
+
+#define GPIO0B7_PU_EN BIT(15)
+
+void spl_board_init(void)
+{
+	/*
+	 * GPIO0_B7 is routed to CAN TX. This SoC pin has a pull-down per default.
+	 * So on power-up, we block the CAN bus with a dominant zero. We want to keep
+	 * this blocking time to a minimum, so we want to get this pin high in SPL.
+	 *
+	 * The CAN driver in Linux disables the pull-down and sets the pin to
+	 * output high. We don't have a CAN driver in U-Boot and don't need one,
+	 * so we just use the easiest way to get the pin high, which is setting a
+	 * pull-up.
+	 */
+	struct rk3588_pmu2_ioc * const ioc = (void *)PMU2_IOC_BASE;
+
+	rk_setreg(&ioc->gpio0b_p, GPIO0B7_PU_EN);
+}

configs/jaguar-rk3588_defconfig

@@ -27,6 +27,7 @@ CONFIG_DEFAULT_FDT_FILE="rockchip/rk3588-jaguar.dtb"
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_CYCLIC=y
 CONFIG_SPL_MAX_SIZE=0x40000
+CONFIG_SPL_BOARD_INIT=y
 # CONFIG_SPL_RAW_IMAGE_SUPPORT is not set
 CONFIG_SPL_ATF=y
 # CONFIG_BOOTM_NETBSD is not set