On Thu, Oct 1, 2015 at 6:13 PM, Maxime Ripard <maxime.rip...@free-electrons.com> wrote: > 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 :)
Sounds good. On the side, I'm wondering if we can put the voltage ranges for important regulators directly in the axp dtsi. It's likely most boards follow the reference design, and will use the regulators accordingly. We could also do this for A31/A31s paired with AXP221/AXP221s. Since I already have a patch for axp221.dtsi, I can incorporate the changes. Let me know what you think. Regards ChenYu -- 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 linux-sunxi+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
