From: Dave Airlie <airlied@gmail.com>
To: dri-devel@lists.freedesktop.org
Subject: [PATCH] drm/mgag200: fix G200ER pll picking algorithm
Date: Thu, 9 Aug 2012 15:04:25 +1000 [thread overview]
Message-ID: <1344488665-26792-1-git-send-email-airlied@gmail.com> (raw)
The original code was misported from the X driver,
a) an int went to unsigned int, breaking the downward counting testm code
b) the port did the vco/computed clock bits completely wrong.
This fixes an infinite loop on modprobe on some Dell servers with the G200ER
chipset variant.
Found in internal testing.
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
---
drivers/gpu/drm/mgag200/mgag200_mode.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index d303061..0201d1d 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -468,10 +468,11 @@ static int mga_g200er_set_plls(struct mga_device *mdev, long clock)
{
unsigned int vcomax, vcomin, pllreffreq;
unsigned int delta, tmpdelta;
- unsigned int testr, testn, testm, testo;
+ int testr, testn, testm, testo;
unsigned int p, m, n;
- unsigned int computed;
+ unsigned int computed, vco;
int tmp;
+ const unsigned int m_div_val[] = { 1, 2, 4, 8 };
m = n = p = 0;
vcomax = 1488000;
@@ -490,12 +491,13 @@ static int mga_g200er_set_plls(struct mga_device *mdev, long clock)
if (delta == 0)
break;
for (testo = 5; testo < 33; testo++) {
- computed = pllreffreq * (testn + 1) /
+ vco = pllreffreq * (testn + 1) /
(testr + 1);
- if (computed < vcomin)
+ if (vco < vcomin)
continue;
- if (computed > vcomax)
+ if (vco > vcomax)
continue;
+ computed = vco / (m_div_val[testm] * (testo + 1));
if (computed > clock)
tmpdelta = computed - clock;
else
--
1.7.10.4
reply other threads:[~2012-08-09 5:04 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1344488665-26792-1-git-send-email-airlied@gmail.com \
--to=airlied@gmail.com \
--cc=dri-devel@lists.freedesktop.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.