* Tomi Valkeinen <tomi.valkeinen@xxxxxx> [120927 23:15]: > On Thu, 2012-09-27 at 11:51 -0700, Tony Lindgren wrote: > > * Tony Lindgren <tony@xxxxxxxxxxx> [120927 11:45]: > > > * Tomi Valkeinen <tomi.valkeinen@xxxxxx> [120927 00:20]: > > > > > > > I could be mistaken how to HW works (but it does work like that for > > > > dss), but sounds to me that uart and gpio drivers (and perhaps some > > > > others, I didn't go through all the pins) need similar pin->regulator > > > > mapping as you suggested for omapdss. > > > > > > Yes it seems that there are supply voltage regulator domains > > > that are specific to some subsystems. I wonder if these are needed > > > in all mux modes, or only when the pins are muxed for that particular > > > subsystem? It could be that the documentation is missing some > > > information here.. > > > > > > For example, what happens if you try to use some vdds_dsi powered > > > pin in GPIO mode without vdds_dsi? > > I have not tested that. > > > Seems like this may provide some clues from "3.6 Power-up and Power-down": > > > > "If the SDI, DSI, or CSI2 and CSIb interfaces are used in standard > > LVCMOS mode (that is, GPIO mode) rather than PHY mode (that is, serial > > differential mode), then vdds_sdi, vdds_dsi, vdds_csi2, and vdds_csib > > may also be connected to vdds. Please, see the recommended SDI, DSI, > > CSI2, and CSIb power supply noise of Table 3-5, Recommended Operating > > Conditions." > > > > So based on that it seems that tweaking of the regulators for these > > pins is only needed for DSS etc, not for GPIO or serial usage. > > I don't read the above paragraph the same way. > > What I think it means is that if, say, a board does not use DSI at all, > the vdds_dsi input pin in OMAP could be connected to vdds instead of the > normal DSI power from the TWL chip, thus making the OMAP's vdds_dsi > "always on". Which means that in some boards the vdds_dsi in TWL is not > needed if the pins are used. > > However, that doesn't mean that the vdds_dsi input is always connected > to vdds if the pins are used for non-DSI uses. A board may well use only > some of the DSI pins for display, leaving the rest free for other uses. > E.g. on omap3 there are 6 DSI pins, and a display panel could well use > only 4 of them. If the 2 other pins are used as GPIOs, handling vdds_dsi > is still required when using those GPIOs. Right, I meant not for typical GPIO usage. The power depends how how it's wired. > So I think the above paragraph confirms that the power for the pins is > indeed required, and handling for the regulator is needed for GPIOs, > uarts, etc. also. And then you most likely are using these pins for SDI, DSI etc and not for GPIO :) But yeah I see your point, if you don't use all DSI pins and use some for GPIOs, you'd also have to take care of the regulators somewhere. Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
