[PATCH 4/4] serial: serial_xen: add DEBUG_UART support

AKASHI Takahiro
2020-10-15T04:25:16Z

By using a hypervisor call, we can implement DEBUG_UART on xen.
This will allow us to see messages even earlier than serial_init().

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
---
drivers/serial/Kconfig | 14 +++++++++++---
drivers/serial/serial_xen.c | 20 ++++++++++++++++++++
2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index e344677f91f6..536cf0641773 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -401,11 +401,19 @@ config DEBUG_UART_MTK
driver will be available until the real driver model serial is
running.

+config DEBUG_UART_XEN
+ bool "XEN Hypervisor Console"
+ depends on XEN_SERIAL
+ help
+ Select this to enable a debug UART using the serial_xen driver. You
+ will not have to provide any parameters to make this work. The driver
+ will be available until the real driver-model serial is running.
+
endchoice

config DEBUG_UART_BASE
hex "Base address of UART"
- depends on DEBUG_UART
+ depends on DEBUG_UART && !DEBUG_UART_XEN
default 0 if DEBUG_UART_SANDBOX
help
This is the base address of your UART for memory-mapped UARTs.
@@ -415,7 +423,7 @@ config DEBUG_UART_BASE

config DEBUG_UART_CLOCK
int "UART input clock"
- depends on DEBUG_UART
+ depends on DEBUG_UART && !DEBUG_UART_XEN
default 0 if DEBUG_UART_SANDBOX
help
The UART input clock determines the speed of the internal UART
@@ -427,7 +435,7 @@ config DEBUG_UART_CLOCK

config DEBUG_UART_SHIFT
int "UART register shift"
- depends on DEBUG_UART
+ depends on DEBUG_UART && !DEBUG_UART_XEN
default 0 if DEBUG_UART
help
Some UARTs (notably ns16550) support different register layouts
diff --git a/drivers/serial/serial_xen.c b/drivers/serial/serial_xen.c
index ed191829f059..34c90ece40fc 100644
--- a/drivers/serial/serial_xen.c
+++ b/drivers/serial/serial_xen.c
@@ -5,6 +5,7 @@
*/
#include <common.h>
#include <cpu_func.h>
+#include <debug_uart.h>
#include <dm.h>
#include <serial.h>
#include <watchdog.h>
@@ -15,11 +16,14 @@
#include <xen/events.h>

#include <xen/interface/sched.h>
+#include <xen/interface/xen.h>
#include <xen/interface/hvm/hvm_op.h>
#include <xen/interface/hvm/params.h>
#include <xen/interface/io/console.h>
#include <xen/interface/io/ring.h>

+#include <asm/xen/hypercall.h>
+
DECLARE_GLOBAL_DATA_PTR;

u32 console_evtchn;
@@ -178,3 +182,19 @@ U_BOOT_DRIVER(serial_xen) = {
.flags = DM_FLAG_PRE_RELOC,
};

+#if defined(CONFIG_DEBUG_UART_XEN)
+static inline void _debug_uart_init(void) {}
+
+static inline void _debug_uart_putc(int c)
+{
+#if CONFIG_IS_ENABLED(ARM)
+ xen_debug_putc(c);
+#else
+ /* the type cast should work on LE only */
+ HYPERVISOR_console_io(CONSOLEIO_write, 1, (char *)&ch);
+#endif
+}
+
+DEBUG_UART_FUNCS
+
+#endif
--
2.28.0