ARM: brcmstb: Add earlyprintk support using run-time checks

The SUN_TOP_CTRL_FAMILY_ID register  is at a fixed absolute address for
all of our supported chips, so utilize its value to determine what the
UARTA base address should be based on the value we read.

Since the code is called both during decompressor when the MMU is off,
and after the MMU has been turned on in the kernel, and we want to do
the lookup only once, we use the same technique as tegra.S and have a
shared storage location between the decompressor and the kernel.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

1 files changed, 145 insertions, 0 deletions

diff --git a/arch/arm/include/debug/brcmstb.S b/arch/arm/include/debug/brcmstb.S
new file mode 100644
index 000000000000..9113d7b33ae0
--- /dev/null
+++ b/arch/arm/include/debug/brcmstb.S
@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2016 Broadcom
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/serial_reg.h>
+
+/* Physical register offset and virtual register offset */
+#define REG_PHYS_BASE		0xf0000000
+#define REG_VIRT_BASE		0xfc000000
+#define REG_PHYS_ADDR(x)	((x) + REG_PHYS_BASE)
+
+/* Product id can be read from here */
+#define SUN_TOP_CTRL_BASE	REG_PHYS_ADDR(0x404000)
+
+#define UARTA_3390		REG_PHYS_ADDR(0x40a900)
+#define UARTA_7250		REG_PHYS_ADDR(0x40b400)
+#define UARTA_7268		REG_PHYS_ADDR(0x40c000)
+#define UARTA_7271		UARTA_7268
+#define UARTA_7364		REG_PHYS_ADDR(0x40b000)
+#define UARTA_7366		UARTA_7364
+#define UARTA_74371		REG_PHYS_ADDR(0x406b00)
+#define UARTA_7439		REG_PHYS_ADDR(0x40a900)
+#define UARTA_7445		REG_PHYS_ADDR(0x40ab00)
+
+#define UART_SHIFT		2
+
+#define checkuart(rp, rv, family_id, family) \
+		/* Load family id */ \
+		ldr	rp, =family_id ; \
+		/* Compare SUN_TOP_CTRL value against it */ \
+		cmp	rp, rv ; \
+		/* Passed test, load address */ \
+		ldreq	rp, =UARTA_##family ; \
+		/* Jump to save UART address */ \
+		beq	91f
+
+		.macro  addruart, rp, rv, tmp
+		adr	\rp, 99f		@ actual addr of 99f
+		ldr	\rv, [\rp]		@ linked addr is stored there
+		sub	\rv, \rv, \rp		@ offset between the two
+		ldr	\rp, [\rp, #4]		@ linked brcmstb_uart_config
+		sub	\tmp, \rp, \rv		@ actual brcmstb_uart_config
+		ldr	\rp, [\tmp]		@ Load brcmstb_uart_config
+		cmp	\rp, #1			@ needs initialization?
+		bne	100f			@ no; go load the addresses
+		mov	\rv, #0			@ yes; record init is done
+		str	\rv, [\tmp]
+
+		/* Check SUN_TOP_CTRL base */
+		ldr	\rp, =SUN_TOP_CTRL_BASE	@ load SUN_TOP_CTRL PA
+		ldr	\rv, [\rp, #0]		@ get register contents
+		and	\rv, \rv, #0xffffff00	@ strip revision bits [7:0]
+
+		/* Chip specific detection starts here */
+20:		checkuart(\rp, \rv, 0x33900000, 3390)
+21:		checkuart(\rp, \rv, 0x72500000, 7250)
+22:		checkuart(\rp, \rv, 0x72680000, 7268)
+23:		checkuart(\rp, \rv, 0x72710000, 7271)
+24:		checkuart(\rp, \rv, 0x73640000, 7364)
+25:		checkuart(\rp, \rv, 0x73660000, 7366)
+26:		checkuart(\rp, \rv, 0x07437100, 74371)
+27:		checkuart(\rp, \rv, 0x74390000, 7439)
+28:		checkuart(\rp, \rv, 0x74450000, 7445)
+
+		/* No valid UART found */
+90:		mov	\rp, #0
+		/* fall through */
+
+		/* Record whichever UART we chose */
+91:		str	\rp, [\tmp, #4]		@ Store in brcmstb_uart_phys
+		cmp	\rp, #0			@ Valid UART address?
+		bne	92f			@ Yes, go process it
+		str	\rp, [\tmp, #8]		@ Store 0 in brcmstb_uart_virt
+		b	100f			@ Done
+92:		and     \rv, \rp, #0xffffff	@ offset within 16MB section
+		add	\rv, \rv, #REG_VIRT_BASE
+		str	\rv, [\tmp, #8]		@ Store in brcmstb_uart_virt
+		b	100f
+
+		.align
+99:		.word	.
+		.word	brcmstb_uart_config
+		.ltorg
+
+		/* Load previously selected UART address */
+100:		ldr	\rp, [\tmp, #4]		@ Load brcmstb_uart_phys
+		ldr	\rv, [\tmp, #8]		@ Load brcmstb_uart_virt
+		.endm
+
+		.macro	store, rd, rx:vararg
+		str	\rd, \rx
+		.endm
+
+		.macro	load, rd, rx:vararg
+		ldr	\rd, \rx
+		.endm
+
+		.macro	senduart,rd,rx
+		store	\rd, [\rx, #UART_TX << UART_SHIFT]
+		.endm
+
+		.macro	busyuart,rd,rx
+1002:		load	\rd, [\rx, #UART_LSR << UART_SHIFT]
+		and	\rd, \rd, #UART_LSR_TEMT | UART_LSR_THRE
+		teq	\rd, #UART_LSR_TEMT | UART_LSR_THRE
+		bne	1002b
+		.endm
+
+		.macro	waituart,rd,rx
+		.endm
+
+/*
+ * Storage for the state maintained by the macros above.
+ *
+ * In the kernel proper, this data is located in arch/arm/mach-bcm/brcmstb.c.
+ * That's because this header is included from multiple files, and we only
+ * want a single copy of the data. In particular, the UART probing code above
+ * assumes it's running using physical addresses. This is true when this file
+ * is included from head.o, but not when included from debug.o. So we need
+ * to share the probe results between the two copies, rather than having
+ * to re-run the probing again later.
+ *
+ * In the decompressor, we put the symbol/storage right here, since common.c
+ * isn't included in the decompressor build. This symbol gets put in .text
+ * even though it's really data, since .data is discarded from the
+ * decompressor. Luckily, .text is writeable in the decompressor, unless
+ * CONFIG_ZBOOT_ROM. That dependency is handled in arch/arm/Kconfig.debug.
+ */
+#if defined(ZIMAGE)
+brcmstb_uart_config:
+	/* Debug UART initialization required */
+	.word 1
+	/* Debug UART physical address */
+	.word 0
+	/* Debug UART virtual address */
+	.word 0
+#endif