[PATCH v4 2/6] clk: renesas: rcar-gen3: Add Z2 clock divider support

[Simon Horman]

On Mon, Jan 29, 2018 at 04:46:37PM +0100, Geert Uytterhoeven wrote:
> Hi Simon,
> 
> On Mon, Jan 29, 2018 at 4:19 PM, Simon Horman <horms at verge.net.au> wrote:
> > On Mon, Jan 29, 2018 at 04:01:49PM +0100, Geert Uytterhoeven wrote:
> >> On Mon, Jan 29, 2018 at 3:24 PM, Simon Horman <horms at verge.net.au> wrote:
> >> > On Fri, Jan 05, 2018 at 03:35:13PM +0100, Geert Uytterhoeven wrote:
> >> >> On Fri, Jan 5, 2018 at 3:04 PM, Simon Horman <horms at verge.net.au> wrote:
> >> >> > On Wed, Jan 03, 2018 at 01:47:08PM +0100, Geert Uytterhoeven wrote:
> >> >> >> On Wed, Jan 3, 2018 at 1:18 PM, Simon Horman <horms+renesas at verge.net.au> wrote:
> >> >> >> > From: Takeshi Kihara <takeshi.kihara.df at renesas.com>
> >> >> >> > This patch adds Z2 clock divider support for R-Car Gen3 SoC.
> >> >> >> >
> >> >> >> > Signed-off-by: Takeshi Kihara <takeshi.kihara.df at renesas.com>
> >> >> >> > Signed-off-by: Simon Horman <horms+renesas at verge.net.au>
> >> >>
> >> >> >> As the CPG/MSSR driver now has suspend/resume support, do we need
> >> >> >> a notifier to restore the Z or Z2 registers? Or is that handled automatically
> >> >> >> by cpufreq during system resume, for both the primary and the secondary
> >> >> >> CPU cores?
> >> >> >
> >> >> > I am a bit unsure.
> >> >> >
> >> >> > When using the A57 cores, which is the default case, the Z clk is queried
> >> >> > by CPUFreq on resume. It appears that on my system its already set to the
> >> >> > correct value but I assume if it was not then it would be reset. However,
> >> >> > this does not cover Z2 clk. So perhaps to be safe we need to register
> >> >> > notifiers and make sure they they play nicely with CPUFreq?
> >> >>
> >> >> Of course the CPU is special: unlike many other devices, it must be running
> >> >> when the kernel is reentered upon system resume.
> >> >> It may be running using a different frequency setting, though.
> >> >> However, following "opp-suspend", the system will always suspend with the
> >> >> Z clock running at 1.5GHz, which is the default?
> >> >> So Z is probably OK.
> >> >>
> >> >> It's more interesting to check what happens when the little cores are
> >> >> enabled as well (unfortunately that requires different firmware).
> >> >> 1. Does cpufreq handle them correctly when they are onlined again during
> >> >>    system resume?
> >> >
> >> > I tested this by updating the firmware on an H3 ES2.0 / Salvator-XS
> >> > using the instructions at
> >> > https://elinux.org/R-Car/Virtualization#Enabling_HYP_Support
> >>
> >> > # grep -E -w "pll[01]|z|z2" /sys/kernel/debug/clk/clk_summary
> >> >           z2                              0            0  1198080000          0 0
> >> >        .pll1                              1            1  3194880000          0 0
> >> >        .pll0                              0            0  2995200000          0 0
> >> >           z                               0            0  1497600000          0 0
> >>
> >> You know it's PLL2, not PLL1, you want to look at? ;-)
> >
> > Sorry, I will double check but I had looked at PLL2 earlier:
> > I just messed things up when preparing things to post in email.
> >
> >> Thanks for checking, looks all good!
> >
> > Ok, so do you think we can merge this series with
> > the off-by-one problem fixed?
> 
> Yes we can. Thanks!

Excellent.