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@matrox.com --- drivers/gpu/drm/mgag200/mgag200_mode.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c index 6b5db83..7337013 100644 --- 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 mga_device *mdev, long clock) 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 mga_device *mdev, long clock) 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; } } }