Messages in this thread | | | From | Stephen Boyd <> | Subject | Re: [PATCH] Revert "clk: fix __clk_init_parent() for single parent clocks" | Date | Tue, 04 Dec 2018 10:05:53 -0800 |
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Quoting Jerome Brunet (2018-12-04 08:32:57) > This reverts commit 2430a94d1e719b7b4af2a65b781a4c036eb22e64. > > From the original commit message: > It turned out a problem because there are some single-parent clocks > that implement .get_parent() callback and return non-zero index. > The SOCFPGA clock is the case; the commit broke the SOCFPGA boards. > > It is wrong for a clock to return an index >= num_parents. CCF checks > for this condition in clk_core_get_parent_by_index(). This function sets > the parent to NULL if index is incoherent, which seems like the only > sane choice. > > commit 2430a94d1e71 ("clk: fix __clk_init_parent() for single parent clocks") > appears to be a work around installed in the core framework for a problem > that is platform specific, and should probably be fixed in the platform code.
Ouch. I see that I even pointed that out in 2016 but never got a reply or a fix patch[1].
> > Further more, it introduces a problem in a corner case of the mux clock. > Take mux with multiple parents, but only one is known, the rest being > undocumented. The register reset has one of unknown parent set. > > Before commit 2430a94d1e71 ("clk: fix __clk_init_parent() for single parent clocks"): > * get_parent() is called, register is read and give an unknown index. > -> the mux is orphaned. > * a call to set_rate() will reparent the mux to the only known parent. > > With commit 2430a94d1e71 ("clk: fix __clk_init_parent() for single parent clocks"): > * the register is never read. > * parent is wrongly assumed to be the only known one. > As a consequence, all the calculation deriving from the mux will be > wrong > * Since we believe the only know parent to be set, set_parent() won't > ever be called and the register won't be set with the correct value.
Isn't this the broken bad case all over again? Why register a clk as a mux and then only say it has one parent?
> > Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> > ---
Is this related to the other patch you sent? Can you send series for related patches please?
[1] https://lkml.kernel.org/r/20160209181833.GA24167@codeaurora.org
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