From b0020d8af991a904de57dbd9a7bc7a61982a6a8c Mon Sep 17 00:00:00 2001
From: Marko Kohtala <marko.kohtala@okoko.fi>
Date: Tue, 18 Jun 2019 10:41:09 +0300
Subject: video: ssd1307fb: Handle width and height that are not multiple of 8
MIME-Version: 1.0
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Git-commit: b0020d8af991a904de57dbd9a7bc7a61982a6a8c
Patch-mainline: v5.4-rc1
References: bsc#1152472

Some displays have dimensions that are not multiple of eight, for example
height of 36, but the driver divided the dimensions by 8. Defining display
to the next multiple of 8 is not good as then the display registers get
configured to dimensions that do not match. This contradicts intructions
by some display manufacturers.

Use DIV_ROUND_UP to multiple of 8 when needed so correct values can be
used.

The ssd1307fb_update_display bit reordering receives a simplification in
the process.

Signed-off-by: Marko Kohtala <marko.kohtala@okoko.fi>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: Michal Vokáč <michal.vokac@ysoft.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190618074111.9309-5-marko.kohtala@okoko.fi
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/video/fbdev/ssd1307fb.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index 4f911480f2eb..8e0720444467 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -150,10 +150,11 @@ static void ssd1307fb_update_display(struct ssd1307fb_par *par)
 {
 	struct ssd1307fb_array *array;
 	u8 *vmem = par->info->screen_buffer;
+	unsigned int line_length = par->info->fix.line_length;
+	unsigned int pages = DIV_ROUND_UP(par->height, 8);
 	int i, j, k;
 
-	array = ssd1307fb_alloc_array(par->width * par->height / 8,
-				      SSD1307FB_DATA);
+	array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA);
 	if (!array)
 		return;
 
@@ -186,22 +187,24 @@ static void ssd1307fb_update_display(struct ssd1307fb_par *par)
 	 *  (5) A4 B4 C4 D4 E4 F4 G4 H4
 	 */
 
-	for (i = 0; i < (par->height / 8); i++) {
+	for (i = 0; i < pages; i++) {
 		for (j = 0; j < par->width; j++) {
+			int m = 8;
 			u32 array_idx = i * par->width + j;
 			array->data[array_idx] = 0;
-			for (k = 0; k < 8; k++) {
-				u32 page_length = par->width * i;
-				u32 index = page_length + (par->width * k + j) / 8;
-				u8 byte = *(vmem + index);
-				u8 bit = byte & (1 << (j % 8));
-				bit = bit >> (j % 8);
+			/* Last page may be partial */
+			if (i + 1 == pages && par->height % 8)
+				m = par->height % 8;
+			for (k = 0; k < m; k++) {
+				u8 byte = vmem[(8 * i + k) * line_length +
+					       j / 8];
+				u8 bit = (byte >> (j % 8)) & 1;
 				array->data[array_idx] |= bit << k;
 			}
 		}
 	}
 
-	ssd1307fb_write_array(par->client, array, par->width * par->height / 8);
+	ssd1307fb_write_array(par->client, array, par->width * pages);
 	kfree(array);
 }
 
@@ -437,7 +440,8 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
 		return ret;
 
 	ret = ssd1307fb_write_cmd(par->client,
-				  par->page_offset + (par->height / 8) - 1);
+				  par->page_offset +
+				  DIV_ROUND_UP(par->height, 8) - 1);
 	if (ret < 0)
 		return ret;
 
@@ -615,7 +619,7 @@ static int ssd1307fb_probe(struct i2c_client *client,
 	par->dclk_div = par->device_info->default_dclk_div;
 	par->dclk_frq = par->device_info->default_dclk_frq;
 
-	vmem_size = par->width * par->height / 8;
+	vmem_size = DIV_ROUND_UP(par->width, 8) * par->height;
 
 	vmem = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 					get_order(vmem_size));
@@ -638,7 +642,7 @@ static int ssd1307fb_probe(struct i2c_client *client,
 
 	info->fbops = &ssd1307fb_ops;
 	info->fix = ssd1307fb_fix;
-	info->fix.line_length = par->width / 8;
+	info->fix.line_length = DIV_ROUND_UP(par->width, 8);
 	info->fbdefio = ssd1307fb_defio;
 
 	info->var = ssd1307fb_var;
-- 
2.28.0