On Wed, Sep 30, 2015 at 12:42:43PM +0200, Hans de Goede wrote: > Hi, > > On 30-09-15 03:52, wens Tsai wrote: > >Hi, > > > >I've been looking into AXP223 usage as part of the RSB patches. > >I found that the recommended voltage for VDD-SYS is 1.1V, but > >we default to 1.2V in U-boot. Among the fex files, some use > >1.1V and some use 1.2V. > > Right, I happened to be looking the same thing recently. > > I've recently bought a bunch of 2nd hand q8 tablets, and I've > pushed all the fex files I got from them to sunxi-boards yesterday. > > Looking at A23 devices only the ippo_q8h_v1.0.fex and > ippo_q8h_v1.2.fex files set VDD-SYS to 1.2 volt, the other > 7 use the recommended 1.1V value. Also note that the gt90h-v4 > tablet which I have does not work with a VDD-SYS of 1.2 volt, > it only works with a VDD-SYS of 1.1 volt. > > I've tested my ippo_q8h_v1.2 and it works fine with a VDD-SYS > of 1.1 volt. > > Looking at A33 devices there are 2 outliers the TZX-723Qa4 and > astar_mid756.fex both set VDD-SYS to 1.26 V, rather then to 1.1 V. > The other 6 all use 1.1V so I believe that 1.1V indeed is a better > default. > > >Perhaps we could update the defconfigs with the values from > >the fex files. > > I think that we should switch the default to 1.1V and then if we see > any issues set it to 1.2V in individual defconfig-s.
Agreed. > >One thing that we have to be careful of is matching the settings > >in U-boot and the kernel, or alternatively, not use a fixed value > >but the recommended range for the VDD-SYS regulator. Accidentally > >dropping the voltage on VDD-SYS results in some logic errors, > >which likely lead to a crash. > > I think it is best to set a range in the dts file and the kernel > just inherit whatever u-boot has set up, this way we don't end > up changing vdd-sys half-way through boot, and we only have one > place where to tweak it if necessary. And here too :) Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
signature.asc
Description: Digital signature
