On Thu, 2012-09-27 at 11:51 -0700, Tony Lindgren wrote: > * Tony Lindgren <t...@atomide.com> [120927 11:45]: > > * Tomi Valkeinen <tomi.valkei...@ti.com> [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. 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. Tomi
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