[PATCH v1] rockchip: include: asm: fix entering download mode rk3066

[Johan Jonker]

When a Rockchip rk3066 board download key is pressed it hangs.
The rk3066 BROM doesn't have support to check the return to BROM,
so when a key is pressed the loop that reads data must be broken
by writing a "-1" to the variable that points to the next page address.
It then goes in download mode and waits for data on USB OTG and UART0.

Signed-off-by: Johan Jonker <jbx6244 at gmail.com>
---
 arch/arm/include/asm/arch-rockchip/boot0.h | 32 +++++++++++++++++++---
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/arch-rockchip/boot0.h b/arch/arm/include/asm/arch-rockchip/boot0.h
index 0c375e543a5e..305461ce3751 100644
--- a/arch/arm/include/asm/arch-rockchip/boot0.h
+++ b/arch/arm/include/asm/arch-rockchip/boot0.h
@@ -3,6 +3,8 @@
  * Copyright 2017 Theobroma Systems Design und Consulting GmbH
  */

+#include <asm/arch-rockchip/boot_mode.h>
+
 /*
  * Execution starts on the instruction following this 4-byte header
  * (containing the magic 'RK30', 'RK31', 'RK32' or 'RK33').  This
@@ -23,17 +25,39 @@
 	 * the first one may be overwritten, if this is the first stage
 	 * contained in the final image created with mkimage)...
 	 */
-	b 1f	 /* if overwritten, entry-address is at the next word */
+	b	1f  /* if overwritten, entry-address is at the next word */
 1:
 #endif
 #if CONFIG_IS_ENABLED(ROCKCHIP_EARLYRETURN_TO_BROM)
-	adr     r3, entry_counter
+#if IS_ENABLED(CONFIG_ROCKCHIP_RK3066)
+/*
+ * Unlike newer Rockchip SoC models the rk3066 BROM code does not have
+ * built-in support to enter download mode after return to BROM code.
+ * Before a return the boot mode register must be checked for the
+ * BOOT_BROM_DOWNLOAD flag. Writing '-1' to a location in SRAM
+ * where the BROM stores the next page address breaks the loop
+ * that reads boot blocks. The boot ROM code then goes into a
+ * download mode and waits for data on USB OTG and UART0.
+ */
+	ldr	r1, =BOOT_BROM_DOWNLOAD
+	ldr	r0, =CONFIG_ROCKCHIP_BOOT_MODE_REG
+	ldr	r0, [r0]
+	cmp	r0, r1           /* if (readl(CONFIG_ROCKCHIP_BOOT_MODE_REG) == */
+	bne	counter_check    /*     BOOT_BROM_DOWNLOAD) {              */
+	ldr	r1, =0xffffffff
+	ldr	r0, =0x10080028
+	str	r1, [r0]         /*     writel(0xffffffff, 0x10080028);    */
+	mov	r0, #1           /*     return 1;                          */
+	bx	lr               /* }                                      */
+counter_check:
+#endif
+	adr	r3, entry_counter
 	ldr	r0, [r3]
 	cmp	r0, #1           /* check if entry_counter == 1 */
 	beq	reset            /* regular bootup */
-	add     r0, #1
+	add	r0, #1
 	str	r0, [r3]         /* increment the entry_counter in memory */
-	mov     r0, #0           /* return 0 to the BROM to signal 'OK' */
+	mov	r0, #0           /* return 0 to the BROM to signal 'OK' */
 	bx	lr               /* return control to the BROM */
 entry_counter:
 	.word   0
--
2.39.2