Hello Mark, On 9 May 2014 19:21, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Fri, May 09, 2014 at 05:50:00PM +0530, Naveen Krishna Ch wrote: >> On 24 April 2014 21:55, Mark Brown <broonie@xxxxxxxxxx> wrote: > >> >> Such solution has been proposed by Mark Brown to fix the problem of >> >> the regulators not beeing available on the peripheral device probe(): >> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2010-March/011971.html > >> > What specifically is this needed for? We *should* be able to use >> > deferred probe for most things, but I know that not all subsystems are >> > able to yet. > >> DRM related drivers like DP, FIMD, HDMI, Mixer wants to be probed ASAP >> during the boot. >> The real problem comes when, one of these drivers do a regulator_get(). > >> If the physical supply is not enabled/hookedup the regulator_get() call >> assumes that physical supply is present and returns a >> "dummy_regulator" (But, not an error). > >> Because of which, Display and several other devices fails to work. > > These drivers are buggy, if they geniunely expect and handle a missing > supply then they should be using regulator_get_optional() to request the > regulator and even if they don't the use of subsys_initcall() is not > going to fix anything here - if a dummy regulator is going to be > returned the time things are probed won't make a difference. We have a situation where.a PMIC is sitting under I2C_TUNNEL with I2C, SPI and SPI uses DMA. PMIC --- I2C_TUNNEL ---- I2C/SPI ---- DMA This PMIC is setting some FETS required for Backlight, LCD and G3D modules. If all the I2C, SPI, DMA, I2C_TUNNEL, DRM based LCD are all mod_probes() DRM drivers are probing a head of the PMIC probe. Which is causing the display drivers to get "dummy_regulators" instead of the real supplies. We couldn't implement -PROBE_DEFER because, the probes are not failing. Should we should check if the return value of regulator_get() is a "dummy_regulator" and then defer the probe /. > >> I2C, I2C_TUNNEL, SPI and DMA drivers are required as subsys_initcall() >> for similar reason. > > What makes you say this? Typically those drivers don't use regulators > at all. I mean I2C, I2C_TUNNEL, SPI and DMA drivers have be to subsys_initcall() to get the PMIC up intime. so, that the system would use the real supplies. This looks like a board specific solution. I guess, this is quite frequent with the buses like I2C, SPI. Kindly, suggest a nicer way. Thanks -- Shine bright, (: Nav :) -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
