On Wed, Aug 22, 2018 at 12:31 AM Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote: > > On Mon, Aug 20, 2018 at 11:28:53PM -0700, Andrey Smirnov wrote: > > A number of PLL pairs (e.g. "sys1_pll1" and "sys1_pll2") share the > > same configuration register, so touching PD bit, as is done for > > SCCG_PLL2 in its prepare/unprepare methods will result in shut down of > > both PLLs. This is very undesireable, since attempting to re-parent a > > clock to "sys1_pll2" might result in complete system shutdown due to > > "sys1_pll1" being shut-down as a part of re-parenting process. > > I can imagine that there are problems with the way it is currently > handled, but the scenario you describe shouldn't happen. "sys1_pll1" > will never be shut down because it doesn't have a disable hook: > > static const struct clk_ops clk_sccg_pll1_ops = { > .is_enabled = clk_pll1_is_prepared, > .recalc_rate = clk_pll1_recalc_rate, > .round_rate = clk_pll1_round_rate, > .set_rate = clk_pll1_set_rate, > }; > > static const struct clk_ops clk_sccg_pll2_ops = { > .enable = clk_pll1_prepare, > .disable = clk_pll1_unprepare, > .recalc_rate = clk_pll2_recalc_rate, > .round_rate = clk_pll2_round_rate, > .set_rate = clk_pll2_set_rate, > }; > > Have I missed something? > Yes, but that's probably due to my explanation being too vague, so let me try again. Both clocks "sys1_pll1" and "sys1_pll2" are controlled/configured via separate bit fields in the _same_ register. That register also has a single "powerdown"/"PD" bit that is shared between both PLLs and affects them both. The way code is currently implemented calling clk_disable() on "sys1_pll2" will clear PD bit and as a result "sys1_pll1" will be shut down as well. This is not that far-fetched of a scenario because a number of derived clocks that go out to individual peripherals are specified with CLK_OPS_PARENT_ENABLE, so trivial clock re-parenting like this one: https://github.com/ndreys/barebox/commit/802d1d5be1f1f3df996ba26b115dd3a55bc10c67 will result in hung system. Hopefully this does a better job of explaining what I was trying to fix. Thanks, Andrey Smirnov _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox