On 2 June 2017 at 10:47, Geert Uytterhoeven <ge...@linux-m68k.org> wrote:
> Hi Wolfram, Ulf, Simon,
>
> While investigating suspend/resume for the R-Car Gen3 clock driver, I
> noticed a clock imbalance for SDHI on Salvator-X.
>
> After boot:
>
> # head -2 /sys/kernel/debug/clk/clk_summary
> clock enable_cnt prepare_cnt rate accuracy phase
> -------------------------------------------------------------
> # grep sd /sys/kernel/debug/clk/clk_summary
> .sdsrc 3 3 399999984 0 0
> sd3 1 1 6250000 0 0
> sdif3 1 2 6250000 0 0
> sd2 1 1 199999992 0 0
> sdif2 1 2 199999992 0 0
> sd1 0 0 199999992 0 0
> sdif1 0 0 199999992 0 0
> sd0 1 1 6250000 0 0
> sdif0 1 2 6250000 0 0
>
> After s2idle suspend/resume:
>
> # grep sd /sys/kernel/debug/clk/clk_summary
> .sdsrc 3 3 399999984 0 0
> sd3 1 1 6250000 0 0
> sdif3 2 2 6250000 0 0
> sd2 1 1 199999992 0 0
> sdif2 2 2 199999992 0 0
> sd1 0 0 199999992 0 0
> sdif1 0 0 199999992 0 0
> sd0 1 1 6250000 0 0
> sdif0 2 2 6250000 0 0
>
> Enable counts are 1 before suspend, and 2 after resume.
>
>
> Boot: Enabled once (also at hardware level):
>
> platform_drv_probe
> renesas_sdhi_sys_dmac_probe
> renesas_sdhi_probe
> tmio_mmc_host_probe
> renesas_sdhi_clk_enable
The driver calls pm_runtime_set_active() during ->probe(), which means
genpd's ->runtime_resume() callback isn't invoked during that point.
In other words, the clocks managed by the clock domain isn't enabled
during ->probe() as genpd's doesn't get to run pm_clk_resume() from
its ->runtime_resume() callback. Unless I am missing something. :-)
I think this is the reason to the following problems. How to fix it?
The driver needs to call pm_runtime_get_sync() instead of
pm_runtime_set_active(), however that may requires some careful
changes if one wants the driver to be able to enable clocks also when
CONFIG_PM is unset. If not, it's pretty easy, else I would do
something like below.
Add a "init" flag to host struct, and set that flag before calling
pm_runtime_get_sync() in ->probe(). When the driver's
->runtime_resume() callbacks get called when the "init" flag is set,
just do an early return 0, as t means ->probe() is running and has
already taken care of the enabling the clock. When probe is done, and
before dropping runtime usage count with pm_runtime_put(), reset the
"init" flag.
>
>
> Suspend: Disabled once (also at hardware level):
>
> suspend_devices_and_enter
> dpm_suspend_start
> dpm_suspend
> __device_suspend
> dpm_run_callback
> pm_runtime_force_suspend
> genpd_runtime_suspend
> pm_generic_runtime_suspend
> tmio_mmc_host_runtime_suspend
> renesas_sdhi_clk_disable
>
>
> Resume: Enabled twice (first one enables at hardware level):
>
> dpm_resume_noirq
> device_resume_noirq
> dpm_run_callback
> pm_genpd_resume_noirq
> pm_runtime_force_resume
> genpd_runtime_resume
> genpd_start_dev
> pm_clk_resume (1)
> __genpd_runtime_resume
> pm_generic_runtime_resume
> tmio_mmc_host_runtime_resume
> renesas_sdhi_clk_enable (2)
>
>
> During subsequent suspends, the clock is disabled twice (last one disables
> at hardware level), as expected:
>
> suspend_devices_and_enter
> dpm_suspend_start
> dpm_suspend
> __device_suspend
> dpm_run_callback
> pm_runtime_force_suspend
> genpd_runtime_suspend
> pm_generic_runtime_suspend
> tmio_mmc_host_runtime_suspend
> renesas_sdhi_clk_disable (1)
> genpd_stop_dev
> pm_clk_suspend (2)
>
>
> From now on, the imbalance is gone.
>
> Note that at boot and initial suspend, genpd does not seem to call into the
> clock domain operations at all.
> Presumable some call to pm_runtime_get_sync() is missing?
>
> Thanks.
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
> ge...@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like
> that.
> -- Linus Torvalds
> --
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Kind regards
Uffe
