[Xen-devel] [RFC PATCH 1/2] xen/arm: Add i.MX8MQ SoCs earlyprintk support

[Amit Singh Tomar <amittomer25@xxxxxxxxx>]

This patch adds earlyprintk support for i.MX8MQ SoC based
boards.

As with most of other debug code for other platforms, uart is
initialized by bootloaders(for instance u-boot[1]).

[1]:https://github.com/u-boot/u-boot/blob/master/drivers/serial/serial_mxc.c#L141

Signed-off-by: Amit Singh Tomar <amittomer25@xxxxxxxxx>
---
 xen/arch/arm/arm64/debug-imx8mq.inc | 54 +++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 xen/arch/arm/arm64/debug-imx8mq.inc

diff --git a/xen/arch/arm/arm64/debug-imx8mq.inc 
b/xen/arch/arm/arm64/debug-imx8mq.inc
new file mode 100644
index 0000000..ec331dc
--- /dev/null
+++ b/xen/arch/arm/arm64/debug-imx8mq.inc
@@ -0,0 +1,54 @@
+/*
+ * xen/arch/arm/arm64/debug-imx8mq.inc
+ *
+ * IMX8MQ specific debug code.
+ *
+ * Copyright (c) 2019, Amit Singh Tomar <amittomer25@xxxxxxxxx>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms and conditions of the GNU General Public
+ * License, version 2, as published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define UTXD            0x40
+#define UTS             0xb4
+#define UTS_TXEMPTY     3<<1
+
+.macro early_uart_init xb, c
+/* Uart has already been initialized by bootloader Firmware, for instance by 
TF-A */
+.endm
+
+/*
+ * IMX8MQ UART wait UART to be ready to transmit
+ * xb: register which contains the UART base address
+ * c: scratch register
+ */
+.macro early_uart_ready xb c
+1:
+        ldr    w\c, [\xb, #UTS]        /* UART Test Register */
+        tbz    w\c, #UTS_TXEMPTY, 1b       /* Check TXEMPTY bit */
+.endm
+
+/*
+ * IMX8MQ UART transmit character
+ * xb: register which contains the UART base address
+ * wt: register which contains the character to transmit
+ */
+.macro early_uart_transmit xb wt
+       str    \wt, [\xb, #UTXD]
+.endm
+
+/*
+ * Local variables:
+ * mode: ASM
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.7.4


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