sunxi: Support the FEL boot mode in the regular u-boot build

So that the CONFIG_SPL_FEL option is not needed anymore. And the regular
SPL binary, generated by the default u-boot build, is now also bootable
over USB in the FEL mode. The SPL still can boot from the SD card too.

A bunch of system registers need to be saved/restored in order to ensure
that the IRQ handler still works in the BROM FEL code after getting
control back from the SPL. This is done in the sunxi code instead of
abusing ifdefs in 'start.S'.

The decision whether to load the main u-boot binary from the SD card or
return to the FEL code in the BROM is done at runtime.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
[hdegoede@redhat.com: Since we now restore various regs before returning to
 the FEL BROM code we can drop the sunxi specific #ifdefs in start.S]
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
index 098a83a..9b49ece 100644 (file)
--- a/arch/arm/cpu/armv7/start.S
+++ b/arch/arm/cpu/armv7/start.S
@@ -54,8 +54,7 @@ save_boot_params_ret:
  * (OMAP4 spl TEXT_BASE is not 32 byte aligned.
  * Continue to use ROM code vector only in OMAP4 spl)
  */
-#if !(defined(CONFIG_OMAP44XX) && defined(CONFIG_SPL_BUILD)) && \
-               !defined(CONFIG_SPL_FEL)
+#if !(defined(CONFIG_OMAP44XX) && defined(CONFIG_SPL_BUILD))
        /* Set V=0 in CP15 SCTLR register - for VBAR to point to vector */
        mrc     p15, 0, r0, c1, c0, 0   @ Read CP15 SCTLR Register
        bic     r0, #CR_V               @ V = 0
@@ -68,9 +67,7 @@ save_boot_params_ret:
 
        /* the mask ROM code should have PLL and others stable */
 #ifndef CONFIG_SKIP_LOWLEVEL_INIT
-#ifndef CONFIG_SPL_FEL
        bl      cpu_init_cp15
-#endif
        bl      cpu_init_crit
 #endif
 

diff --git a/arch/arm/cpu/armv7/sunxi/board.c b/arch/arm/cpu/armv7/sunxi/board.c
index b7492ac..c02c015 100644 (file)
--- a/arch/arm/cpu/armv7/sunxi/board.c
+++ b/arch/arm/cpu/armv7/sunxi/board.c
@@ -30,6 +30,10 @@
 struct fel_stash {
        uint32_t sp;
        uint32_t lr;
+       uint32_t cpsr;
+       uint32_t sctlr;
+       uint32_t vbar;
+       uint32_t cr;
 };
 
 struct fel_stash fel_stash __attribute__((section(".data")));
@@ -108,15 +112,34 @@ void s_init(void)
  */
 u32 spl_boot_device(void)
 {
+#ifdef CONFIG_SPL_FEL
        /*
-        * Have we been asked to return to the FEL portion of the boot ROM?
-        * TODO: We need a more robust test here, or bracket this with
-        * #ifdef CONFIG_SPL_FEL.
+        * This is the legacy compile time configuration for a special FEL
+        * enabled build. It has many restrictions and can only boot over USB.
         */
-       if (fel_stash.lr >= 0xffff0000 && fel_stash.lr < 0xffff4000)
+       return BOOT_DEVICE_BOARD;
+#else
+       /*
+        * When booting from the SD card, the "eGON.BT0" signature is expected
+        * to be found in memory at the address 0x0004 (see the "mksunxiboot"
+        * tool, which generates this header).
+        *
+        * When booting in the FEL mode over USB, this signature is patched in
+        * memory and replaced with something else by the 'fel' tool. This other
+        * signature is selected in such a way, that it can't be present in a
+        * valid bootable SD card image (because the BROM would refuse to
+        * execute the SPL in this case).
+        *
+        * This branch is just making a decision at runtime whether to load
+        * the main u-boot binary from the SD card (if the "eGON.BT0" signature
+        * is found) or return to the FEL code in the BROM to wait and receive
+        * the main u-boot binary over USB.
+        */
+       if (readl(4) == 0x4E4F4765 && readl(8) == 0x3054422E) /* eGON.BT0 */
+               return BOOT_DEVICE_MMC1;
+       else
                return BOOT_DEVICE_BOARD;
-
-       return BOOT_DEVICE_MMC1;
+#endif
 }
 
 /* No confirmation data available in SPL yet. Hardcode bootmode */

diff --git a/arch/arm/cpu/armv7/sunxi/fel_utils.S b/arch/arm/cpu/armv7/sunxi/fel_utils.S
index 0c1de52..bf00335 100644 (file)
--- a/arch/arm/cpu/armv7/sunxi/fel_utils.S
+++ b/arch/arm/cpu/armv7/sunxi/fel_utils.S
@@ -15,11 +15,28 @@ ENTRY(save_boot_params)
        ldr     r0, =fel_stash
        str     sp, [r0, #0]
        str     lr, [r0, #4]
+       mrs     lr, cpsr                @ Read CPSR
+       str     lr, [r0, #8]
+       mrc     p15, 0, lr, c1, c0, 0   @ Read CP15 SCTLR Register
+       str     lr, [r0, #12]
+       mrc     p15, 0, lr, c12, c0, 0  @ Read VBAR
+       str     lr, [r0, #16]
+       mrc     p15, 0, lr, c1, c0, 0   @ Read CP15 Control Register
+       str     lr, [r0, #20]
        b       save_boot_params_ret
 ENDPROC(save_boot_params)
 
 ENTRY(return_to_fel)
        mov     sp, r0
        mov     lr, r1
+       ldr     r0, =fel_stash
+       ldr     r1, [r0, #20]
+       mcr     p15, 0, r1, c1, c0, 0   @ Write CP15 Control Register
+       ldr     r1, [r0, #16]
+       mcr     p15, 0, r1, c12, c0, 0  @ Write VBAR
+       ldr     r1, [r0, #12]
+       mcr     p15, 0, r1, c1, c0, 0   @ Write CP15 SCTLR Register
+       ldr     r1, [r0, #8]
+       msr     cpsr, r1                @ Write CPSR
        bx      lr
 ENDPROC(return_to_fel)