linux-kernel - [PATCH AUTOSEL 5.6 06/47] efi/earlycon: Fix early printk for wider fonts

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Date:   Thu, 28 May 2020 07:55:19 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dave Young <dyoung@...hat.com>, Ard Biesheuvel <ardb@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-efi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.6 06/47] efi/earlycon: Fix early printk for wider fonts

From: Dave Young <dyoung@...hat.com>

[ Upstream commit 8f592ada59b321d248391bae175cd78a12972223 ]

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@...hat.com>
Link: https://lore.kernel.org/r/20200412024927.GA6884@dhcp-128-65.nay.redhat.com
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 5d4f84781aa0..a52236e11e5f 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;
-- 
2.25.1