[U-Boot] [PATCH v3 5/6] rockchip: back-to-bootrom: rk3188: chain from SPL via TPL to the BROM

[Philipp Tomsich <philipp.tomsich@theobroma-systems.com>]

The RK3188 implementation previously passed the address of the stack
frame created during save_boot_params via pmu->os_reg[2]. This was not
strictly necessary, as the save_boot_params() function was called
twice (first: for TPL, saving the context for the BROM; next: for SPL,
saving the context for the TPL) and a back-to-bootrom from the SPL
would thus return to TPL.

To simplify things, we now assume that the state of the TPL is not
corrupted during SPL (the binaries are non-overlapping) and that the
SPL can safely return to TPL using the back-to-bootrom mechanism.
Consequently, the TPL should expect the SPL to return control and then
further return to the actual bootrom by performing another
back-to-bootrom transition.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
---

Changes in v3: None
Changes in v2:
- [added in v2] chain back_to_bootrom calls for SPL, first returning
  to the TPL (using the same mechanism) and the to the BROM from the
  TPL

 arch/arm/mach-rockchip/rk3188-board-spl.c | 10 ----------
 arch/arm/mach-rockchip/rk3188-board-tpl.c | 17 ++++++++++-------
 2 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/arch/arm/mach-rockchip/rk3188-board-spl.c b/arch/arm/mach-rockchip/rk3188-board-spl.c
index d3866bf..05d4ae6 100644
--- a/arch/arm/mach-rockchip/rk3188-board-spl.c
+++ b/arch/arm/mach-rockchip/rk3188-board-spl.c
@@ -101,7 +101,6 @@ static int setup_arm_clock(void)
 void board_init_f(ulong dummy)
 {
 	struct udevice *pinctrl, *dev;
-	struct rk3188_pmu *pmu;
 	int ret;
 
 	/* Example code showing how to enable the debug UART on RK3188 */
@@ -145,15 +144,6 @@ void board_init_f(ulong dummy)
 		return;
 	}
 
-	/*
-	 * Recover the bootrom's stackpointer.
-	 * For whatever reason needs to run after rockchip_get_clk.
-	 */
-	pmu = syscon_get_first_range(ROCKCHIP_SYSCON_PMU);
-	if (IS_ERR(pmu))
-		error("pmu syscon returned %ld\n", PTR_ERR(pmu));
-	SAVE_SP_ADDR = readl(&pmu->sys_reg[2]);
-
 	ret = uclass_get_device(UCLASS_PINCTRL, 0, &pinctrl);
 	if (ret) {
 		debug("Pinctrl init failed: %d\n", ret);
diff --git a/arch/arm/mach-rockchip/rk3188-board-tpl.c b/arch/arm/mach-rockchip/rk3188-board-tpl.c
index b458ef6..c714278 100644
--- a/arch/arm/mach-rockchip/rk3188-board-tpl.c
+++ b/arch/arm/mach-rockchip/rk3188-board-tpl.c
@@ -21,15 +21,16 @@ static int rk3188_num_entries __attribute__ ((section(".data")));
 
 static void jump_to_spl(void)
 {
-	typedef void __noreturn (*image_entry_noargs_t)(void);
+	typedef void (*image_entry_noargs_t)(void);
 
-	struct rk3188_pmu * const pmu = (void *)PMU_BASE;
 	image_entry_noargs_t tpl_entry =
 		(image_entry_noargs_t)(unsigned long)SPL_ENTRY;
 
-	/* Store the SAVE_SP_ADDR in a location shared with SPL. */
-	writel(SAVE_SP_ADDR, &pmu->sys_reg[2]);
 	tpl_entry();
+	/*
+	 * If the SPL stage triggers a 'return to bootrom', it will
+	 * return to here.
+	 */
 }
 
 void board_init_f(ulong dummy)
@@ -77,10 +78,12 @@ void board_init_f(ulong dummy)
 		back_to_bootrom();
 	} else {
 		/*
-		 * TPL part of the loader should now wait for us
-		 * at offset 0xC00 in the sram. Should never return
-		 * from there.
+		 * SPL part of the loader should now wait for us at
+		 * offset 0xC00 in the sram. If the SPL returns to us,
+		 * we should in turn return to the BROM (i.e. chain
+		 * through).
 		 */
 		jump_to_spl();
+		back_to_bootrom();
 	}
 }
-- 
2.1.4