linux-kernel - [ 59/98] drm/mgag200: Bug fix: Modified pll algorithm for EH project

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 26 Mar 2013 15:42:48 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Julia Lemire <jlemire@...rox.com>,
	Dave Airlie <airlied@...hat.com>
Subject: [ 59/98] drm/mgag200: Bug fix: Modified pll algorithm for EH project

3.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Julia Lemire <jlemire@...rox.com>

commit 260b3f1291a75a580d22ce8bfb1499c617272716 upstream.

While testing the mgag200 kms driver on the HP ProLiant Gen8, a
bug was seen.  Once the bootloader would load the selected kernel,
the screen would go black.  At first it was assumed that the
mgag200 kms driver was hanging.  But after setting up the grub
serial output, it was seen that the driver was being loaded
properly.  After trying serval monitors, one finaly displayed
the message "Frequency Out of Range".  By comparing the kms pll
algorithm with the previous mgag200 xorg driver pll algorithm,
discrepencies were found.  Once the kms pll algorithm was
modified, the expected pll values were produced.  This fix was
tested on several monitors of varying native resolutions.

Signed-off-by: Julia Lemire <jlemire@...rox.com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/mgag200/mgag200_mode.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -382,19 +382,19 @@ static int mga_g200eh_set_plls(struct mg
 	m = n = p = 0;
 	vcomax = 800000;
 	vcomin = 400000;
-	pllreffreq = 3333;
+	pllreffreq = 33333;
 
 	delta = 0xffffffff;
 	permitteddelta = clock * 5 / 1000;
 
-	for (testp = 16; testp > 0; testp--) {
+	for (testp = 16; testp > 0; testp >>= 1) {
 		if (clock * testp > vcomax)
 			continue;
 		if (clock * testp < vcomin)
 			continue;
 
 		for (testm = 1; testm < 33; testm++) {
-			for (testn = 1; testn < 257; testn++) {
+			for (testn = 17; testn < 257; testn++) {
 				computed = (pllreffreq * testn) /
 					(testm * testp);
 				if (computed > clock)
@@ -404,11 +404,11 @@ static int mga_g200eh_set_plls(struct mg
 				if (tmpdelta < delta) {
 					delta = tmpdelta;
 					n = testn - 1;
-					m = (testm - 1) | ((n >> 1) & 0x80);
+					m = (testm - 1);
 					p = testp - 1;
 				}
 				if ((clock * testp) >= 600000)
-					p |= 80;
+					p |= 0x80;
 			}
 		}
 	}


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/