Ulf Hansson [off-list ref] writes:

On 28 January 2016 at 17:33, Jon Hunter [off-list ref] wrote:

quoted

Adds generic PM support to the PMC driver where the PM domains are
populated from device-tree and the PM domain consumer devices are
bound to their relevant PM domains via device-tree as well.

Update the tegra_powergate_sequence_power_up() API so that internally
it calls the same tegra_powergate_xxx functions that are used by the
tegra generic power domain code for consistency.

This is based upon work by Thierry Reding [off-list ref]
and Vince Hsu [off-list ref].

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>

[...]

quoted

+static void tegra_powergate_disable_clocks(struct tegra_powergate *pg)
+{
+       unsigned int i;
+
+       for (i = 0; i < pg->num_clks; i++)
+               clk_disable_unprepare(pg->clks[i]);
+}
+
+static int tegra_powergate_enable_clocks(struct tegra_powergate *pg)
+{
+       unsigned int i;
+       int err;
+
+       for (i = 0; i < pg->num_clks; i++) {
+               err = clk_prepare_enable(pg->clks[i]);
+               if (err)
+                       goto out;
+       }
+
+       return 0;
+
+out:
+       while (i--)
+               clk_disable_unprepare(pg->clks[i]);
+
+       return err;
+}

I have seen similar code around in other PM domains, dealing with
enabling/disabling a *list* of clocks.
Perhaps we should invent a new clock API that helps with this to
prevents code duplication!?

What about the pm_clk_* API which was built for tracking clocks
associated with devices for runtime PM.

IOW, you could pm_clk_add(pg->pmc->dev, pg->clks[i]) and then your
_enable_clocks() would become pm_clk_suspend() an dyour
_disable_clocks() would become pm_clk_resume().

I might not be following the mapping between PMC and PGs though so not
sure pg->pmc->dev is the right struct device, but you get the idea.

Kevin