[PATCH v4 03/16] input: Flush the keyboard buffer before resetting it

[Simon Glass]

If U-Boot is not the first-stage bootloader the keyboard may already be
set up. Make sure to flush any data before trying to reset it. This
avoids a long timeout / hang.

Add some comments and a log category while we are here.

Signed-off-by: Simon Glass <sjg at chromium.org>
Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
---

(no changes since v2)

Changes in v2:
- Flush the buffer instead of skipping the reset

 drivers/input/i8042.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/input/i8042.c b/drivers/input/i8042.c
index 3563dc98838..e6070ca0152 100644
--- a/drivers/input/i8042.c
+++ b/drivers/input/i8042.c
@@ -6,6 +6,8 @@
 
 /* i8042.c - Intel 8042 keyboard driver routines */
 
+#define LOG_CATEGORY UCLASS_KEYBOARD
+
 #include <common.h>
 #include <dm.h>
 #include <env.h>
@@ -54,6 +56,14 @@ static unsigned char ext_key_map[] = {
 	0x00  /* map end */
 	};
 
+/**
+ * kbd_input_empty() - Wait until the keyboard is ready for a command
+ *
+ * Checks the IBF flag (input buffer full), waiting for it to indicate that
+ * any previous command has been processed.
+ *
+ * Return: true if ready, false if it timed out
+ */
 static int kbd_input_empty(void)
 {
 	int kbd_timeout = KBD_TIMEOUT * 1000;
@@ -64,6 +74,12 @@ static int kbd_input_empty(void)
 	return kbd_timeout != -1;
 }
 
+/**
+ * kbd_output_full() - Wait until the keyboard has data available
+ *
+ * Checks the OBF flag (output buffer full), waiting for it to indicate that
+ * a response to a previous command is available
+ */
 static int kbd_output_full(void)
 {
 	int kbd_timeout = KBD_TIMEOUT * 1000;
@@ -127,6 +143,9 @@ static int kbd_reset(int quirk)
 {
 	int config;
 
+	if (!kbd_input_empty())
+		goto err;
+
 	/* controller self test */
 	if (kbd_cmd_read(CMD_SELF_TEST) != KBC_TEST_OK)
 		goto err;
-- 
2.40.1.521.gf1e218fcd8-goog