Hi guys,

On 01/25/2018 06:24 PM, JeffyChen wrote:
On 01/25/2018 05:42 PM, Randy Li wrote:



confirmed with Simon, there might be some iommus don't have a pd, and
We use the pd to control the NIU node(not on upstream), without a pd or
fake pd, none of the platform would work.
after talked offline, it's possible to have iommu without pd in upstream
kernel(and chromeos kernel), but on our internal kernel, the drivers
would require pd(or fake pd) to reset modules when error happens.

anyway, i think that means we do need clock control here.

found another reason to not depend on pd to control clocks.

currently we are using pd's pm_clk to keep clocks enabled during power on. but in our pd binding doc, that is not needed: - clocks (optional): phandles to clocks which need to be enabled while power domain
        switches state.

confirmed with Caesar, the pm_clk only required for some old chips(rk3288 for example) due to hardware issue.

and i tested my chromebook kevin(rk3399), it works well after remove the pm_clk:

+++ b/drivers/soc/rockchip/pm_domains.c
@@ -478,7 +478,6 @@ static int rockchip_pm_add_one_domain(struct rockchip_pmu *pmu,
        pd->genpd.power_on = rockchip_pd_power_on;
        pd->genpd.attach_dev = rockchip_pd_attach_dev;
        pd->genpd.detach_dev = rockchip_pd_detach_dev;
-       pd->genpd.flags = GENPD_FLAG_PM_CLK;

will do more tests and send patch tomorrow.


the CONFIG_PM could be disabled.I am hard to believe a modern platform
can work without that.

so it might be better to control clocks in iommu driver itself.
I won't
insist how the version of the iommu patch on the upstream, I
just post an idea here.
The version for kernel 4.4 is under internal review, the implementation
has been modified many times.

I would suggest the managing clocks in pd is a more easy way and don't
need to spare those thing in two places.


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