[U-Boot] [PATCH 00/12] Enable returning back to BootROM from spear SPL

[U-Boot] [PATCH 00/12] Enable returning back to BootROM from spear SPL

[Miquel Raynal]

Spear machines currently have only the possibility to boot from NOR
while an interesting alternative exist: booting from USB. For this,
the BootROM will enumerate an USB device and wait for a RAM driver
(likely, the SPL). It will load the driver in SRAM and jump to
it. Once the initialization done, the SPL must return back into the
BootROM so that another enumeration occurs allowing the user to upload
the full Bootloader (eg. U-Boot). The BootROM will finally load the
file in RAM and jump into it.

Most of the patches are cleanups and preparation work to ease the
reading of the main assembly file.

The last patch is a fallback on USB Boot if the NOR is empty or
corrupted. Of course if USB boot has not been enabled, nothing will
happen.

Tested on a custom board featuring a SPEAr600.

Hope this change will find users!

Thanks,
Miquèl


Miquel Raynal (12):
  spl: Fix typo in kernel doc
  arm: spear: Drop useless board_init_r call
  arm: spear: Call the SPL 'SPL', not 'Xloader'
  arm: spear: Drop false comment
  arm: spear: Fix the main comment in start.S
  arm: spear: Purely cosmetic changes in start.S
  arm: spear: Use PUSH/POP mnemonics when relevant
  arm: spear: Reference the link register with LR instead of R14
  arm: spear: Simplify start.S organization
  arm: spear: Support returning to BootROM
  arm: spear: Do not link the _main branch
  arm: spear: Return to BootROM if failing to boot from the main device

 arch/arm/cpu/arm926ejs/spear/spl.c   | 47 +++++++++++++++++++++--
 arch/arm/cpu/arm926ejs/spear/start.S | 56 +++++++++++-----------------
 common/spl/spl.c                     |  2 +-
 3 files changed, 66 insertions(+), 39 deletions(-)

-- 
2.19.1

[U-Boot] [PATCH 01/12] spl: Fix typo in kernel doc

[Miquel Raynal]

Fix a tiny typo in boot_from_devices() kernel doc.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 common/spl/spl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/common/spl/spl.c b/common/spl/spl.c
index 88d4b8a9bf..745da7d431 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -532,7 +532,7 @@ static int spl_load_image(struct spl_image_info *spl_image,
 }
 
 /**
- * boot_from_devices() - Try loading an booting U-Boot from a list of devices
+ * boot_from_devices() - Try loading a booting U-Boot from a list of devices
  *
  * @spl_image: Place to put the image details if successful
  * @spl_boot_list: List of boot devices to try
-- 
2.19.1

[U-Boot] [PATCH 02/12] arm: spear: Drop useless board_init_r call

[Miquel Raynal]

It is clearly stated that board_init_f should *not* call
board_init_r. Indeed, board_init_f should return. The code will
continue through arch/arm/lib/crt0.S which will do more setup before
calling board_init_r.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/spl.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/spl.c b/arch/arm/cpu/arm926ejs/spear/spl.c
index d2bddb589a..b004cccafd 100644
--- a/arch/arm/cpu/arm926ejs/spear/spl.c
+++ b/arch/arm/cpu/arm926ejs/spear/spl.c
@@ -251,6 +251,4 @@ void board_init_f(ulong dummy)
 	puts("Configure DDR\n");
 	mpmc_init();
 	spear_late_init();
-
-	board_init_r(NULL, 0);
 }
-- 
2.19.1

[U-Boot] [PATCH 03/12] arm: spear: Call the SPL 'SPL', not 'Xloader'

[Miquel Raynal]

Rename Xloader as SPL in comments.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index 1cab4ca6fb..e69deb7926 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -33,14 +33,14 @@
 
 reset:
 /*
- * Xloader has to return back to BootROM in a few cases.
+ * SPL has to return back to BootROM in a few cases.
  * eg. Ethernet boot, UART boot, USB boot
  * Saving registers for returning back
  */
 	stmdb	sp!, {r0-r12,r14}
 	bl	cpu_init_crit
 /*
- * Clearing bss area is not done in Xloader.
+ * Clearing bss area is not done in SPL.
  * BSS area lies in the DDR location which is not yet initialized
  * bss is assumed to be uninitialized.
  */
-- 
2.19.1

[U-Boot] [PATCH 04/12] arm: spear: Drop false comment

[Miquel Raynal]

SPL BSS lies in SRAM and is actually initialized to 0 by the SPL in
arch/arm/lib/crt0.S:_main(), which is called by cpu_init_crit.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index e69deb7926..4395985549 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -39,11 +39,6 @@ reset:
  */
 	stmdb	sp!, {r0-r12,r14}
 	bl	cpu_init_crit
-/*
- * Clearing bss area is not done in SPL.
- * BSS area lies in the DDR location which is not yet initialized
- * bss is assumed to be uninitialized.
- */
 	ldmia	sp!, {r0-r12,pc}
 
 /*
-- 
2.19.1

[U-Boot] [PATCH 05/12] arm: spear: Fix the main comment in start.S

[Miquel Raynal]

This comment describes the board state at the moment where we enter
the SPL. The description is entirely wrong; re-write it to fit the
reality.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index 4395985549..c3bb58c55b 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -21,10 +21,9 @@
  *
  * Startup Code (reset vector)
  *
- * Below are the critical initializations already taken place in BootROM.
- * So, these are not taken care in Xloader
- * 1. Relocation to RAM
- * 2. Initializing stacks
+ * The BootROM already initialized its own stack in the [0-0xb00] reserved
+ * range of the SRAM. The SPL (in _main) will update the stack pointer to
+ * its own SRAM area (right before the gd section).
  *
  *************************************************************************
  */
-- 
2.19.1

[U-Boot] [PATCH 06/12] arm: spear: Purely cosmetic changes in start.S

[Miquel Raynal]

Before cleaning a bit further the spear/start.S file, apply a few
cosmetic changes: capital letters, comment indentation and small
rewriting.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index c3bb58c55b..566cf668b7 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -31,11 +31,10 @@
 	.globl	reset
 
 reset:
-/*
- * SPL has to return back to BootROM in a few cases.
- * eg. Ethernet boot, UART boot, USB boot
- * Saving registers for returning back
- */
+	/*
+	* SPL has to return back to BootROM in a few cases (eg. Ethernet boot,
+	* UART boot, USB boot): save registers in BootROM's stack.
+	*/
 	stmdb	sp!, {r0-r12,r14}
 	bl	cpu_init_crit
 	ldmia	sp!, {r0-r12,pc}
@@ -52,14 +51,14 @@ reset:
  */
 cpu_init_crit:
 	/*
-	 * flush v4 I/D caches
+	 * Flush v4 I/D caches
 	 */
 	mov	r0, #0
-	mcr	p15, 0, r0, c7, c7, 0	/* flush v3/v4 cache */
-	mcr	p15, 0, r0, c8, c7, 0	/* flush v4 TLB */
+	mcr	p15, 0, r0, c7, c7, 0	/* Flush v3/v4 cache */
+	mcr	p15, 0, r0, c8, c7, 0	/* Flush v4 TLB */
 
 	/*
-	 * enable instruction cache
+	 * Enable instruction cache
 	 */
 	mrc	p15, 0, r0, c1, c0, 0
 	orr	r0, r0, #0x00001000	/* set bit 12 (I) I-Cache */
-- 
2.19.1

[U-Boot] [PATCH 07/12] arm: spear: Use PUSH/POP mnemonics when relevant

[Miquel Raynal]

Quoting ARM "RealView Compilation Tools Assembler Guide v4.0":

        PUSH and POP are synonyms for STMDB and LDM (or LDMIA), with
        the base register sp (r13), and the adjusted address written
        back to the base register.
	PUSH and POP are the preferred mnemonic in these cases.

Let's follow this recommandation to ease the reading and substitute
LDMIA/STMDB operations with PUSH/POP mnemonics.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index 566cf668b7..25895f01ac 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -35,9 +35,9 @@ reset:
 	* SPL has to return back to BootROM in a few cases (eg. Ethernet boot,
 	* UART boot, USB boot): save registers in BootROM's stack.
 	*/
-	stmdb	sp!, {r0-r12,r14}
+	push	{r0-r12,r14}
 	bl	cpu_init_crit
-	ldmia	sp!, {r0-r12,pc}
+	pop	{r0-r12,pc}
 
 /*
  *************************************************************************
@@ -67,6 +67,6 @@ cpu_init_crit:
 	/*
 	 * Go setup Memory and board specific bits prior to relocation.
 	 */
-	stmdb	sp!, {lr}
+	push	{lr}
 	bl	_main	/* _main will call board_init_f */
-	ldmia	sp!, {pc}
+	pop	{pc}
-- 
2.19.1

[U-Boot] [PATCH 08/12] arm: spear: Reference the link register with LR instead of R14

[Miquel Raynal]

The link register is stored in R14. ARM assembly code allows to use
the 'lr' name to reference it instead of 'r14' which is not very
meaningful. Do the substitution to ease the reading.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index 25895f01ac..2bc9d5990e 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -35,7 +35,7 @@ reset:
 	* SPL has to return back to BootROM in a few cases (eg. Ethernet boot,
 	* UART boot, USB boot): save registers in BootROM's stack.
 	*/
-	push	{r0-r12,r14}
+	push	{r0-r12,lr}
 	bl	cpu_init_crit
 	pop	{r0-r12,pc}
 
-- 
2.19.1

[U-Boot] [PATCH 09/12] arm: spear: Simplify start.S organization

[Miquel Raynal]

There is no reason to do the few spear-related initialization, in a
different procedure than 'reset'. Spare one branching and get a linear
code flow by removing this indirection.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index 2bc9d5990e..5fb2bd12ec 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -36,20 +36,7 @@ reset:
 	* UART boot, USB boot): save registers in BootROM's stack.
 	*/
 	push	{r0-r12,lr}
-	bl	cpu_init_crit
-	pop	{r0-r12,pc}
 
-/*
- *************************************************************************
- *
- * CPU_init_critical registers
- *
- * setup important registers
- * setup memory timing
- *
- *************************************************************************
- */
-cpu_init_crit:
 	/*
 	 * Flush v4 I/D caches
 	 */
@@ -67,6 +54,6 @@ cpu_init_crit:
 	/*
 	 * Go setup Memory and board specific bits prior to relocation.
 	 */
-	push	{lr}
 	bl	_main	/* _main will call board_init_f */
-	pop	{pc}
+
+	pop	{r0-r12,pc}
-- 
2.19.1

[U-Boot] [PATCH 10/12] arm: spear: Support returning to BootROM

[Miquel Raynal]

Implement the weak board_return_to_bootrom() function so that when
enabling the spl_bootrom.c driver, one can make use of usbboot on
spear platforms. All necessary information to return to the BootROM
are stored in the BootROM's stack. The SPL stack pointer is reset so
we save the BootROM's stack pointer into the SPL .data section.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/spl.c   | 35 ++++++++++++++++++++++++++--
 arch/arm/cpu/arm926ejs/spear/start.S |  7 +++++-
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/spl.c b/arch/arm/cpu/arm926ejs/spear/spl.c
index b004cccafd..b2cacf2d3e 100644
--- a/arch/arm/cpu/arm926ejs/spear/spl.c
+++ b/arch/arm/cpu/arm926ejs/spear/spl.c
@@ -16,6 +16,12 @@
 #include <asm/arch/spr_syscntl.h>
 #include <linux/mtd/st_smi.h>
 
+/* Reserve some space to store the BootROM's stack pointer during SPL operation.
+ * The BSS cannot be used for this purpose because it will be zeroed after
+ * having stored the pointer, so force the location to the data section.
+ */
+u32 bootrom_stash_sp __attribute__((section(".data")));
+
 static void ddr_clock_init(void)
 {
 	struct misc_regs *misc_p = (struct misc_regs *)CONFIG_SPEAR_MISCBASE;
@@ -223,8 +229,9 @@ u32 spl_boot_device(void)
 {
 	u32 mode = 0;
 
-	/* Currently only SNOR is supported as the only */
-	if (snor_boot_selected()) {
+	if (usb_boot_selected()) {
+		mode = BOOT_DEVICE_BOOTROM;
+	} else if (snor_boot_selected()) {
 		/* SNOR-SMI initialization */
 		snor_init();
 
@@ -252,3 +259,27 @@ void board_init_f(ulong dummy)
 	mpmc_init();
 	spear_late_init();
 }
+
+/*
+ * In a few cases (Ethernet, UART or USB boot, we might want to go back into the
+ * BootROM code right after having initialized a few components like the DRAM).
+ * The following function is called from SPL common code (board_init_r).
+ */
+void board_return_to_bootrom(void)
+{
+	/*
+	 * Retrieve the BootROM's stack pointer and jump back to the start of
+	 * the SPL, where we can easily branch back into the BootROM. Don't do
+	 * it right here because SPL might be compiled in Thumb mode while the
+	 * BootROM expects ARM mode.
+	 */
+	asm volatile ("ldr r0, =bootrom_stash_sp;"
+		      "ldr r0, [r0];"
+		      "mov sp, r0;"
+#if defined(CONFIG_SPL_SYS_THUMB_BUILD)
+		      "blx back_to_bootrom;"
+#else
+		      "bl back_to_bootrom;"
+#endif
+		      );
+}
diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index 5fb2bd12ec..2cf854eb74 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -29,13 +29,17 @@
  */
 
 	.globl	reset
+	.globl	back_to_bootrom
 
 reset:
 	/*
 	* SPL has to return back to BootROM in a few cases (eg. Ethernet boot,
-	* UART boot, USB boot): save registers in BootROM's stack.
+	* UART boot, USB boot): save registers in BootROM's stack and then the
+	* BootROM's stack pointer in the SPL's data section.
 	*/
 	push	{r0-r12,lr}
+	ldr	r0, =bootrom_stash_sp
+	str	sp, [r0]
 
 	/*
 	 * Flush v4 I/D caches
@@ -56,4 +60,5 @@ reset:
 	 */
 	bl	_main	/* _main will call board_init_f */
 
+back_to_bootrom:
 	pop	{r0-r12,pc}
-- 
2.19.1

[U-Boot] [PATCH 11/12] arm: spear: Do not link the _main branch

[Miquel Raynal]

The _main call is not supposed to return at all: don't link the
branch.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/start.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/cpu/arm926ejs/spear/start.S b/arch/arm/cpu/arm926ejs/spear/start.S
index 2cf854eb74..9ac96291b7 100644
--- a/arch/arm/cpu/arm926ejs/spear/start.S
+++ b/arch/arm/cpu/arm926ejs/spear/start.S
@@ -57,8 +57,9 @@ reset:
 
 	/*
 	 * Go setup Memory and board specific bits prior to relocation.
+	 * This call is not supposed to return.
 	 */
-	bl	_main	/* _main will call board_init_f */
+	b	_main	/* _main will call board_init_f */
 
 back_to_bootrom:
 	pop	{r0-r12,pc}
-- 
2.19.1

[U-Boot] [PATCH 12/12] arm: spear: Return to BootROM if failing to boot from the main device

[Miquel Raynal]

Overload the weak function board_boot_order() so that besides choosing
the main boot device, we can fallback on USB boot by returning in the
BootROM, eg. if the NOR flash is empty while it was the primary boot
medium.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 arch/arm/cpu/arm926ejs/spear/spl.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm/cpu/arm926ejs/spear/spl.c b/arch/arm/cpu/arm926ejs/spear/spl.c
index b2cacf2d3e..fc332fb626 100644
--- a/arch/arm/cpu/arm926ejs/spear/spl.c
+++ b/arch/arm/cpu/arm926ejs/spear/spl.c
@@ -241,6 +241,18 @@ u32 spl_boot_device(void)
 	return mode;
 }
 
+void board_boot_order(u32 *spl_boot_list)
+{
+	spl_boot_list[0] = spl_boot_device();
+
+	/*
+	 * If the main boot device (eg. NOR) is empty, try to jump back into the
+	 * BootROM for USB boot process.
+	 */
+	if (USB_BOOT_SUPPORTED)
+		spl_boot_list[1] = BOOT_DEVICE_BOOTROM;
+}
+
 void board_init_f(ulong dummy)
 {
 	struct misc_regs *misc_p = (struct misc_regs *)CONFIG_SPEAR_MISCBASE;
-- 
2.19.1

[U-Boot] [PATCH 01/12] spl: Fix typo in kernel doc

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> Fix a tiny typo in boot_from_devices() kernel doc.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 02/12] arm: spear: Drop useless board_init_r call

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> It is clearly stated that board_init_f should *not* call
> board_init_r. Indeed, board_init_f should return. The code will
> continue through arch/arm/lib/crt0.S which will do more setup before
> calling board_init_r.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 03/12] arm: spear: Call the SPL 'SPL', not 'Xloader'

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> Rename Xloader as SPL in comments.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 04/12] arm: spear: Drop false comment

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> SPL BSS lies in SRAM and is actually initialized to 0 by the SPL in
> arch/arm/lib/crt0.S:_main(), which is called by cpu_init_crit.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 05/12] arm: spear: Fix the main comment in start.S

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> This comment describes the board state at the moment where we enter
> the SPL. The description is entirely wrong; re-write it to fit the
> reality.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 06/12] arm: spear: Purely cosmetic changes in start.S

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> Before cleaning a bit further the spear/start.S file, apply a few
> cosmetic changes: capital letters, comment indentation and small
> rewriting.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 07/12] arm: spear: Use PUSH/POP mnemonics when relevant

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> Quoting ARM "RealView Compilation Tools Assembler Guide v4.0":
> 
>          PUSH and POP are synonyms for STMDB and LDM (or LDMIA), with
>          the base register sp (r13), and the adjusted address written
>          back to the base register.
> 	PUSH and POP are the preferred mnemonic in these cases.
> 
> Let's follow this recommandation to ease the reading and substitute
> LDMIA/STMDB operations with PUSH/POP mnemonics.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 08/12] arm: spear: Reference the link register with LR instead of R14

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> The link register is stored in R14. ARM assembly code allows to use
> the 'lr' name to reference it instead of 'r14' which is not very
> meaningful. Do the substitution to ease the reading.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 09/12] arm: spear: Simplify start.S organization

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> There is no reason to do the few spear-related initialization, in a
> different procedure than 'reset'. Spare one branching and get a linear
> code flow by removing this indirection.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 10/12] arm: spear: Support returning to BootROM

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> Implement the weak board_return_to_bootrom() function so that when
> enabling the spl_bootrom.c driver, one can make use of usbboot on
> spear platforms. All necessary information to return to the BootROM
> are stored in the BootROM's stack. The SPL stack pointer is reset so
> we save the BootROM's stack pointer into the SPL .data section.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 11/12] arm: spear: Do not link the _main branch

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> The _main call is not supposed to return at all: don't link the
> branch.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 12/12] arm: spear: Return to BootROM if failing to boot from the main device

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> Overload the weak function board_boot_order() so that besides choosing
> the main boot device, we can fallback on USB boot by returning in the
> BootROM, eg. if the NOR flash is empty while it was the primary boot
> medium.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

[U-Boot] [PATCH 00/12] Enable returning back to BootROM from spear SPL

[Stefan Roese]

On 07.05.19 14:18, Miquel Raynal wrote:
> Spear machines currently have only the possibility to boot from NOR
> while an interesting alternative exist: booting from USB. For this,
> the BootROM will enumerate an USB device and wait for a RAM driver
> (likely, the SPL). It will load the driver in SRAM and jump to
> it. Once the initialization done, the SPL must return back into the
> BootROM so that another enumeration occurs allowing the user to upload
> the full Bootloader (eg. U-Boot). The BootROM will finally load the
> file in RAM and jump into it.
> 
> Most of the patches are cleanups and preparation work to ease the
> reading of the main assembly file.
> 
> The last patch is a fallback on USB Boot if the NOR is empty or
> corrupted. Of course if USB boot has not been enabled, nothing will
> happen.
> 
> Tested on a custom board featuring a SPEAr600.
> 
> Hope this change will find users!

Many thanks for working on this and improving the neglected SPEAr
U-Boot port. It's quite some time since I worked on this platform
and I still do have a x600 board hidden somewhere. Frankly, if
there is no real need I will not dig this board up to update and
test a new U-Boot version on it (sorry).

Thanks,
Stefan

[U-Boot] [PATCH 00/12] Enable returning back to BootROM from spear SPL

[Miquel Raynal]

Hi Stefan,

Stefan Roese <sr@denx.de> wrote on Tue, 7 May 2019 14:50:02 +0200:

> On 07.05.19 14:18, Miquel Raynal wrote:
> > Spear machines currently have only the possibility to boot from NOR
> > while an interesting alternative exist: booting from USB. For this,
> > the BootROM will enumerate an USB device and wait for a RAM driver
> > (likely, the SPL). It will load the driver in SRAM and jump to
> > it. Once the initialization done, the SPL must return back into the
> > BootROM so that another enumeration occurs allowing the user to upload
> > the full Bootloader (eg. U-Boot). The BootROM will finally load the
> > file in RAM and jump into it.
> > 
> > Most of the patches are cleanups and preparation work to ease the
> > reading of the main assembly file.
> > 
> > The last patch is a fallback on USB Boot if the NOR is empty or
> > corrupted. Of course if USB boot has not been enabled, nothing will
> > happen.
> > 
> > Tested on a custom board featuring a SPEAr600.
> > 
> > Hope this change will find users!  
> 
> Many thanks for working on this and improving the neglected SPEAr
> U-Boot port. It's quite some time since I worked on this platform
> and I still do have a x600 board hidden somewhere. Frankly, if
> there is no real need I will not dig this board up to update and
> test a new U-Boot version on it (sorry).

Absolutely no problem, thanks for reviewing!

Miquèl

[U-Boot] [PATCH 01/12] spl: Fix typo in kernel doc

[Tom Rini]

On Tue, May 07, 2019 at 02:18:43PM +0200, Miquel Raynal wrote:

> Fix a tiny typo in boot_from_devices() kernel doc.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 02/12] arm: spear: Drop useless board_init_r call

[Tom Rini]

On Tue, May 07, 2019 at 02:18:44PM +0200, Miquel Raynal wrote:

> It is clearly stated that board_init_f should *not* call
> board_init_r. Indeed, board_init_f should return. The code will
> continue through arch/arm/lib/crt0.S which will do more setup before
> calling board_init_r.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 03/12] arm: spear: Call the SPL 'SPL', not 'Xloader'

[Tom Rini]

On Tue, May 07, 2019 at 02:18:45PM +0200, Miquel Raynal wrote:

> Rename Xloader as SPL in comments.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 04/12] arm: spear: Drop false comment

[Tom Rini]

On Tue, May 07, 2019 at 02:18:46PM +0200, Miquel Raynal wrote:

> SPL BSS lies in SRAM and is actually initialized to 0 by the SPL in
> arch/arm/lib/crt0.S:_main(), which is called by cpu_init_crit.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 05/12] arm: spear: Fix the main comment in start.S

[Tom Rini]

On Tue, May 07, 2019 at 02:18:47PM +0200, Miquel Raynal wrote:

> This comment describes the board state at the moment where we enter
> the SPL. The description is entirely wrong; re-write it to fit the
> reality.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 06/12] arm: spear: Purely cosmetic changes in start.S

[Tom Rini]

On Tue, May 07, 2019 at 02:18:48PM +0200, Miquel Raynal wrote:

> Before cleaning a bit further the spear/start.S file, apply a few
> cosmetic changes: capital letters, comment indentation and small
> rewriting.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 07/12] arm: spear: Use PUSH/POP mnemonics when relevant

[Tom Rini]

On Tue, May 07, 2019 at 02:18:49PM +0200, Miquel Raynal wrote:

> Quoting ARM "RealView Compilation Tools Assembler Guide v4.0":
> 
>         PUSH and POP are synonyms for STMDB and LDM (or LDMIA), with
>         the base register sp (r13), and the adjusted address written
>         back to the base register.
> 	PUSH and POP are the preferred mnemonic in these cases.
> 
> Let's follow this recommandation to ease the reading and substitute
> LDMIA/STMDB operations with PUSH/POP mnemonics.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 08/12] arm: spear: Reference the link register with LR instead of R14

[Tom Rini]

On Tue, May 07, 2019 at 02:18:50PM +0200, Miquel Raynal wrote:

> The link register is stored in R14. ARM assembly code allows to use
> the 'lr' name to reference it instead of 'r14' which is not very
> meaningful. Do the substitution to ease the reading.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 09/12] arm: spear: Simplify start.S organization

[Tom Rini]

On Tue, May 07, 2019 at 02:18:51PM +0200, Miquel Raynal wrote:

> There is no reason to do the few spear-related initialization, in a
> different procedure than 'reset'. Spare one branching and get a linear
> code flow by removing this indirection.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 10/12] arm: spear: Support returning to BootROM

[Tom Rini]

On Tue, May 07, 2019 at 02:18:52PM +0200, Miquel Raynal wrote:

> Implement the weak board_return_to_bootrom() function so that when
> enabling the spl_bootrom.c driver, one can make use of usbboot on
> spear platforms. All necessary information to return to the BootROM
> are stored in the BootROM's stack. The SPL stack pointer is reset so
> we save the BootROM's stack pointer into the SPL .data section.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 11/12] arm: spear: Do not link the _main branch

[Tom Rini]

On Tue, May 07, 2019 at 02:18:53PM +0200, Miquel Raynal wrote:

> The _main call is not supposed to return at all: don't link the
> branch.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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[U-Boot] [PATCH 12/12] arm: spear: Return to BootROM if failing to boot from the main device

[Tom Rini]

On Tue, May 07, 2019 at 02:18:54PM +0200, Miquel Raynal wrote:

> Overload the weak function board_boot_order() so that besides choosing
> the main boot device, we can fallback on USB boot by returning in the
> BootROM, eg. if the NOR flash is empty while it was the primary boot
> medium.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Reviewed-by: Stefan Roese <sr@denx.de>

Applied to u-boot/master, thanks!

-- 
Tom
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