Messages in this thread | | | Subject | Re: [PATCH] cpufreq: imx: Add cpufreq driver for imx7D/Solo SOC | From | Bai Ping <> | Date | Tue, 24 Nov 2015 19:08:13 +0800 |
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On 2015/11/24 17:08, Lucas Stach wrote: > Am Dienstag, den 24.11.2015, 15:35 +0800 schrieb Bai Ping: >> On 2015/11/23 17:40, Lucas Stach wrote: >>> Am Montag, den 23.11.2015, 22:07 +0800 schrieb Bai Ping: >>>> The i.MX7Dual/Solo is a new series of the i.MX SOC family. >>>> The existing cpufreq driver for 'i.MX6' or 'cpufreq-dt' can >>>> NOT match the requirement of this new SOC. This patch adds the >>>> cpufreq driver for i.MX7Dual/Solo. >>>> >>> So, what are those requirements, which could not be matched with >>> cpufreq-dt? We should really try to not add another cpufreq driver. >> the requirement is the PLL1 used to source the CPU core clock can NOT >> change frequency on the fly, >> during the PLL1 frequency change, not clock output from this PLL1 in a >> short time. this will lead to glitch >> to the core clock. so before we change the PLL1's frequency, we must >> switch the CPU core clock to another >> clock source, after the PLL1 frequency has been changed, we switch back >> core clock to PLL1. >>> I don't see anything special in here. A single regulator and some clocks >>> needing to be controlled in the right way. That's already handled for >>> i.MX5 with cpufreq-dt. Please look up how it is done there and try to do >>> it the same way for MX7, or provide substantial information why it >>> couldn't be done. >> I have checked the i.MX5 cpufreq, As on i.MX5, no need to take care of >> the PLL's frequency change flow, >> so the cpufreq-dt is the best one to support cpufreq. But on i.MX7, the >> PLL design is not the same as on i.MX5, >> additional steps needed in CPU frequency changing flow. the issue that >> can NOT be tackled by cpufreq-dt is >> additional step used by PLL frequency change. > This is wrong, we have the step clock requirement on MX5 as well, that's > why I asked you to look into this. The MX5 clock controller provides a > virtual ARM clock, that implements the proper clock switch flow. This > allows to reuse cpufreq-dt, thus reducing code duplication in the > cpufreq drivers greatly. Thanks for your reminder. It is my fault, I missed the imx_clk_cpu function. I will try using cpufreq-dt on i.MX7 just like i.MX5.
BR Jacky Bai > > Regards, > Lucas >
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