[PATCH v2] efi_loader: Improve console screen clearing and reset

[Jan Kiszka]

From: Jan Kiszka <jan.kiszka at siemens.com>

Before clearing the screen, ensure that no previous output of firmware
or UEFI programs will be overwritten on serial devices or other
streaming consoles. This helps generating complete boot logs.

Tested regarding multi-output against qemu-x86_defconfig.

Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
---

Changes in v2:
 - rebased and tested against more scenarios, sucessfully

 lib/efi_loader/efi_console.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/lib/efi_loader/efi_console.c b/lib/efi_loader/efi_console.c
index 60a3fc85ac4..0270b20bafe 100644
--- a/lib/efi_loader/efi_console.c
+++ b/lib/efi_loader/efi_console.c
@@ -463,8 +463,18 @@ static efi_status_t EFIAPI efi_cout_set_attribute(
 static efi_status_t EFIAPI efi_cout_clear_screen(
 			struct efi_simple_text_output_protocol *this)
 {
+	unsigned int row;
+
 	EFI_ENTRY("%p", this);
 
+	/* Avoid overwriting previous outputs on streaming consoles */
+	for (row = 1; row < efi_cout_modes[efi_con_mode.mode].rows; row++)
+		printf("\n");
+
+	/* Set default colors if not done yet */
+	if (efi_con_mode.attribute == 0)
+		efi_cout_set_attribute(this, 0x07);
+
 	/*
 	 * The Linux console wants both a clear and a home command. The video
 	 * uclass does not support <ESC>[H without coordinates, yet.
@@ -522,9 +532,9 @@ static efi_status_t EFIAPI efi_cout_reset(
 {
 	EFI_ENTRY("%p, %d", this, extended_verification);
 
-	/* Set default colors */
-	efi_con_mode.attribute = 0x07;
-	printf(ESC "[0;37;40m");
+	/* Trigger reset to default colors */
+	efi_con_mode.attribute = 0;
+
 	/* Clear screen */
 	EFI_CALL(efi_cout_clear_screen(this));
 
-- 
2.35.3