On Wed, 2010-04-21 at 16:46 +0800, ykzhao wrote: > On Sat, 2010-04-10 at 05:14 +0800, Eric Anholt wrote: > > As far as I can tell from reading the specs, this patch just completely > > breaks TV detect on GM45. And the logic of "set all the bits for the > > register setting we're going to do and then if it's gm45 skip a few of > > them" is unintuitive and backwards, even if it was correct.\\ > > This is from bios code. And the bios team also helps to confirm that TV > DAC sense state bits should be cleared to zero on cantiga platform.
Uh. The patch does this: > + if (IS_GM45(dev)) > + tv_dac &= ~(TVDAC_STATE_CHG_EN | TVDAC_A_SENSE_CTL | > + TVDAC_B_SENSE_CTL | TVDAC_C_SENSE_CTL); > + TVDAC_STATE_CHG_EN is documented as: > TVDAC_STATE_CHG_EN : Enables DAC state change detection logic > 0 = disabled > 1 = enabled You mean to tell me that, on Cantiga, _disabling_ the state change detection logic, enables state change detection? > How about the following commit log? > > The TV detection logic is not reliable on the cantiga platform. Sometimes > the > TV will be misdetected as the following two cases: > a. TV is misdetected on some laptops. e.g. There is no TV connector > port or no TV is attaced. But the TV is shown as connected. > b. TV connector type is misdetected. E.g. the component TV is > attached, but the TV is shown as S-video type. > > It is confirmed that in bios code the TV DAC sense bits should be cleared > to zero on GM45 in course of TV detection, which is different with other > platforms. It uses the following conditional definition: > IF CTG > TVDAC_SENSE_CTL EQU 0 ; Cantiga to Low level > ELSE > TVDAC_SENSE_CTL EQU BIT27 + BIT26 + BIT25 + BIT24 > ENDIF ; CTG If the BIOS clears all those bits in TV_DAC, _then_ enables bit 27, then this seems like a reasonable thing to do. That would mean that the detection logic is basically one shot, and needs to be completely reset between uses. But I really don't see how, short of a really really bad hardware bug, turning a subsystem _off_ would make that subsystem work. - ajax
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