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drm/nv17-nv4x: Fix analog load detection false positive on rare occasions.

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On some boards the residual current DAC outputs can draw when they're
disconnected can be high enough to give a false load detection
positive (I've only seen it in the S-video luma output of some cards,
but just to be sure). The output line capacitance is limited and
sampling twice should fix it reliably.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
This commit is contained in:
Francisco Jerez 2010-08-30 15:37:57 +02:00 committed by Ben Skeggs
parent 9d59e8a1fc
commit 7314dec95c
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/nouveau/nv04_dac.c
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@ -291,6 +291,8 @@ uint32_t nv17_dac_sample_load(struct drm_encoder *encoder)
msleep(5);
sample = NVReadRAMDAC(dev, 0, NV_PRAMDAC_TEST_CONTROL + regoffset);
/* do it again just in case it's a residual current */
sample &= NVReadRAMDAC(dev, 0, NV_PRAMDAC_TEST_CONTROL + regoffset);
temp = NVReadRAMDAC(dev, head, NV_PRAMDAC_TEST_CONTROL);
NVWriteRAMDAC(dev, head, NV_PRAMDAC_TEST_CONTROL,