[PATCH V4 2/2] xen/arm: Add i.MX lpuart early printk support

["Peng Fan (OSS)" <peng.fan@xxxxxxxxxxx>]

From: Peng Fan <peng.fan@xxxxxxx>

Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
---
 xen/arch/arm/Kconfig.debug              | 14 +++++++
 xen/arch/arm/arm64/debug-imx-lpuart.inc | 52 +++++++++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 xen/arch/arm/arm64/debug-imx-lpuart.inc

diff --git a/xen/arch/arm/Kconfig.debug b/xen/arch/arm/Kconfig.debug
index 35ccd13273..842d768280 100644
--- a/xen/arch/arm/Kconfig.debug
+++ b/xen/arch/arm/Kconfig.debug
@@ -58,6 +58,16 @@ choice
                        This option is preferred over the platform specific
                        options; the platform specific options are deprecated
                        and will soon be removed.
+       config EARLY_UART_CHOICE_IMX_LPUART
+               select EARLY_UART_IMX_LPUART
+               depends on ARM_64
+               bool "Early printk via i.MX LPUART"
+               help
+                       Say Y here if you wish the early printk to direct their
+                       output to a i.MX LPUART. You can use this option to
+                       provide the parameters for the i.MX LPUART rather than
+                       selecting one of the platform specific options below if
+                       you know the parameters for the port.
        config EARLY_UART_CHOICE_MESON
                select EARLY_UART_MESON
                depends on ARM_64
@@ -186,6 +196,9 @@ config EARLY_UART_CADENCE
 config EARLY_UART_EXYNOS4210
        select EARLY_PRINTK
        bool
+config EARLY_UART_IMX_LPUART
+       select EARLY_PRINTK
+       bool
 config EARLY_UART_MESON
        select EARLY_PRINTK
        bool
@@ -283,6 +296,7 @@ config EARLY_PRINTK_INC
        default "debug-8250.inc" if EARLY_UART_8250
        default "debug-cadence.inc" if EARLY_UART_CADENCE
        default "debug-exynos4210.inc" if EARLY_UART_EXYNOS4210
+       default "debug-imx-lpuart.inc" if EARLY_UART_IMX_LPUART
        default "debug-meson.inc" if EARLY_UART_MESON
        default "debug-mvebu.inc" if EARLY_UART_MVEBU
        default "debug-pl011.inc" if EARLY_UART_PL011
diff --git a/xen/arch/arm/arm64/debug-imx-lpuart.inc 
b/xen/arch/arm/arm64/debug-imx-lpuart.inc
new file mode 100644
index 0000000000..f68252da86
--- /dev/null
+++ b/xen/arch/arm/arm64/debug-imx-lpuart.inc
@@ -0,0 +1,52 @@
+/*
+ * xen/arch/arm/arm64/debug-imx-lpuart.inc
+ *
+ * i.MX8QM specific debug code
+ *
+ * Peng Fan <peng.fan@xxxxxxx>
+ * Copyright 2022 NXP
+ *
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <asm/imx-lpuart.h>
+
+.macro early_uart_init wb wc wd
+/* Already initialized in bootloader */
+.endm
+
+/*
+ * Wait LPUART to be ready to transmit
+ * rb: register which contains the UART base address
+ * rc: scratch register
+ */
+.macro early_uart_ready xb, c
+1:
+        ldr   w\c, [\xb, #UARTSTAT]   /* <- Flag register */
+        tst   w\c, #UARTSTAT_TDRE     /* Check FIFO EMPTY bit */
+        beq   1b                      /* Wait for the UART to be ready */
+.endm
+
+/*
+ * LPUART transmit character
+ * rb: register which contains the UART base address
+ * rt: register which contains the character to transmit
+ */
+.macro early_uart_transmit xb, wt
+        str   \wt, [\xb, #UARTDATA]  /* -> Data Register */
+.endm
+
+/*
+ * Local variables:
+ * mode: ASM
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.35.1