[tip: efi/urgent] efi/earlycon: Fix early printk for wider fonts

[tip-bot2 for Dave Young]

The following commit has been merged into the efi/urgent branch of tip:

Commit-ID:     8f592ada59b321d248391bae175cd78a12972223
Gitweb:        https://git.kernel.org/tip/8f592ada59b321d248391bae175cd78a12972223
Author:        Dave Young <dyoung@xxxxxxxxxx>
AuthorDate:    Sun, 12 Apr 2020 10:49:27 +08:00
Committer:     Ard Biesheuvel <ardb@xxxxxxxxxx>
CommitterDate: Tue, 12 May 2020 12:29:45 +02:00

efi/earlycon: Fix early printk for wider fonts

When I play with terminus fonts I noticed the efi early printk does
not work because the earlycon code assumes font width is 8.

Here add the code to adapt with larger fonts.  Tested with all kinds
of kernel built-in fonts on my laptop. Also tested with a local draft
patch for 14x28 !bold terminus font.

Signed-off-by: Dave Young <dyoung@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200412024927.GA6884@xxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 drivers/firmware/efi/earlycon.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/firmware/efi/earlycon.c b/drivers/firmware/efi/earlycon.c
index 5d4f847..a52236e 100644
--- a/drivers/firmware/efi/earlycon.c
+++ b/drivers/firmware/efi/earlycon.c
@@ -114,14 +114,16 @@ static void efi_earlycon_write_char(u32 *dst, unsigned char c, unsigned int h)
 	const u32 color_black = 0x00000000;
 	const u32 color_white = 0x00ffffff;
 	const u8 *src;
-	u8 s8;
-	int m;
+	int m, n, bytes;
+	u8 x;
 
-	src = font->data + c * font->height;
-	s8 = *(src + h);
+	bytes = BITS_TO_BYTES(font->width);
+	src = font->data + c * font->height * bytes + h * bytes;
 
-	for (m = 0; m < 8; m++) {
-		if ((s8 >> (7 - m)) & 1)
+	for (m = 0; m < font->width; m++) {
+		n = m % 8;
+		x = *(src + m / 8);
+		if ((x >> (7 - n)) & 1)
 			*dst = color_white;
 		else
 			*dst = color_black;