[PATCH v2] clk: sunxi-ng: a733: Keep SCP firmware bus clocks enabled

[Enzo Adriano <enzo.adriano.code@gmail.com>]

The A733 PRCM's bus-r-riscv and bus-r-msgbox gates have no Linux
consumers, so unused-clock cleanup gates them. With vendor SCP firmware
running on the E902 as shipped on Cubie A7S, warm reboot then stalls.

Keep both critical until remoteproc/mailbox drivers can claim them.
This follows A523 bus-r-cpucfg in commit 1dba74abf3e2 ("clk: sunxi-ng:
Mark A523 bus-r-cpucfg clock as critical") and the temporary SCPI firmware
clock protection for Meson AXG fclk_div3 in drivers/clk/meson/axg.c.

On Cubie A7S with vendor boot0/BL31/SCP/U-Boot and without
clk_ignore_unused, warm reboot returns with both clocks critical and
stalls without them. Vinicius found either flag alone insufficient on
Cubie A7Z. Power-off, suspend, single flags on A7S, other
boards/firmware and upstream TF-A were not tested.

Link: https://lore.kernel.org/r/20261005183038.417798-1-vinicius.eduardo.pedrosa@gmail.com
Signed-off-by: Enzo Adriano <enzo.adriano.code@gmail.com>
---
Changes in v2:
- Drop r-timer0, bus-r-timer and bus-msgbox0: A7S warm reboot works with
  these at 0/0. Keep only the two E902/mailbox bus gates after Junhui's
  review, pending remoteproc/mailbox ownership.
- Rebase on CCU v7; its PRCM clock definitions are unchanged from v6.

v1:
https://lore.kernel.org/r/20261031020640-263f7b05-a7s-clock@gmail.com

Base: v7.4-rc1. Depends on CCU v7 (all eight patches):
https://lore.kernel.org/r/20261112-a733-clk-v7-0-db7c5451ffa2@pigmoral.tech

November 12 board test: two RAM boots and warm reboot -f returns on
Cubie A7S with vendor boot0/BL31/SCP/U-Boot, without clk_ignore_unused.
Both retained clocks were 1/1; all three dropped clocks were 0/0.
The no-flag stall was observed with CCU v6 on Nov 10; PRCM code is
byte-identical in v7, where the no-flag control was not repeated.
Runtime used DT v3 and its dependencies (all four UART v2 patches),
with the PMIC identifier and pinctrl IRQ-map context adapted to the base:
https://lore.kernel.org/r/cover.1794227241.git.enzo.adriano.code@gmail.com

 drivers/clk/sunxi-ng/ccu-sun60i-a733-r.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu-sun60i-a733-r.c b/drivers/clk/sunxi-ng/ccu-sun60i-a733-r.c
index b8f6e8c6e507..f2965daba0d3 100644
--- a/drivers/clk/sunxi-ng/ccu-sun60i-a733-r.c
+++ b/drivers/clk/sunxi-ng/ccu-sun60i-a733-r.c
@@ -108,7 +108,9 @@ static SUNXI_CCU_DUALDIV_MUX_GATE(r_spi_clk, "r-spi", r_spi_parents, 0x150,
 				  0);
 static SUNXI_CCU_GATE_HW(bus_r_spi_clk, "bus-r-spi", &r_ahb_clk.common.hw, 0x15c, BIT(0), 0);
 
-static SUNXI_CCU_GATE_HW(bus_r_msgbox_clk, "bus-r-msgbox", &r_ahb_clk.common.hw, 0x17c, BIT(0), 0);
+/* Vendor SCP firmware on E902 needs this until a remoteproc/mailbox driver claims it. */
+static SUNXI_CCU_GATE_HW(bus_r_msgbox_clk, "bus-r-msgbox", &r_ahb_clk.common.hw,
+			 0x17c, BIT(0), CLK_IS_CRITICAL);
 
 static SUNXI_CCU_GATE_HW(bus_r_uart0_clk, "bus-r-uart0", &r_apb1_clk.common.hw, 0x18c, BIT(0), 0);
 static SUNXI_CCU_GATE_HW(bus_r_uart1_clk, "bus-r-uart1", &r_apb1_clk.common.hw, 0x18c, BIT(1), 0);
@@ -146,8 +148,9 @@ static SUNXI_CCU_MUX_DATA_WITH_GATE(r_riscv_clk, "r-riscv", r_riscv_parents, 0x2
 				  24, 2,	/* mux */
 				  BIT(31),	/* gate */
 				  0);
+/* Vendor SCP firmware on E902 needs this until a remoteproc/mailbox driver claims it. */
 static SUNXI_CCU_GATE_HW(bus_r_riscv_clk, "bus-r-riscv", &r_apb0_clk.common.hw,
-			 0x21c, BIT(0), 0);
+			 0x21c, BIT(0), CLK_IS_CRITICAL);
 static SUNXI_CCU_GATE_HW(bus_r_riscv_cfg_clk, "bus-r-riscv-cfg", &r_apb0_clk.common.hw,
 			 0x21c, BIT(1), 0);
 

base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.53.0