From mboxrd@z Thu Jan 1 00:00:00 1970 From: hramrach@gmail.com (Michal Suchanek) Date: Fri, 15 Jul 2016 16:22:31 +0200 Subject: [linux-sunxi] Re: [PATCH v2 06/14] ARM: sun8i: clk: Add clk-factor rate application method In-Reply-To: <98fd2ab2-9b1d-1494-5867-7701780fd471@megous.com> References: <20160625034511.7966-1-megous@megous.com> <20160625034511.7966-7-megous@megous.com> <20160630204001.GC5485@lukather> <0b71ed7e-98c9-109e-85e6-ceb95131d88a@megous.com> <20160715085356.GR4761@lukather> <085e185a-ac76-dd3f-9b0e-a7dc9c0c09f3@megous.com> <20160715152756.db7375a7109fed18c2fbf43a@free.fr> <98fd2ab2-9b1d-1494-5867-7701780fd471@megous.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello, On 15 July 2016 at 15:48, Ond?ej Jirman wrote: > > > On 15.7.2016 15:27, Jean-Francois Moine wrote: >> On Fri, 15 Jul 2016 12:38:54 +0200 >> Ond?ej Jirman wrote: >> >>>> If so, then yes, trying to switch to the 24MHz oscillator before >>>> applying the factors, and then switching back when the PLL is stable >>>> would be a nice solution. >>>> >>>> I just checked, and all the SoCs we've had so far have that >>>> possibility, so if it works, for now, I'd like to stick to that. >>> >>> It would need to be tested. U-boot does the change only once, while the >>> kernel would be doing it all the time and between various frequencies >>> and PLL settings. So the issues may show up with this solution too. >> >> I don't think this is a good idea: the CPU clock may be changed at any >> time with the CPUFreq governor. I don't see the system moving from >> 1008MHz to 24MHz and then to 1200MHz when some computation is needed! > > PLL lock time is around 10-20us, I'd guess based on the number of loops > in the PLL lock wait loop. So unless you'll be switching frequencies > many times per second, this should be barely noticeable. > > But I'd like a different solution too. Do you have a patch to test this? For me changing CPU frequency on Orange Pi One always locks up the system. I keep running it on the u-boot setup 1.08GHz at 1.1V Thanks Michal