Messages in this thread | | | Date | Thu, 30 Jul 2015 12:41:07 +0200 | From | Nicolas Ferre <> | Subject | Re: [PATCH v4] clk: at91: add generated clock driver |
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Le 29/07/2015 09:15, Boris Brezillon a écrit : > Hi Nicolas, > > On Tue, 28 Jul 2015 18:08:05 +0200 > Nicolas Ferre <nicolas.ferre@atmel.com> wrote: > > >> +static void clk_generated_startup(struct clk_generated *gck) >> +{ >> + struct at91_pmc *pmc = gck->pmc; >> + u32 tmp; >> + >> + pmc_lock(pmc); >> + pmc_write(pmc, AT91_PMC_PCR, (gck->id & AT91_PMC_PCR_PID_MASK)); >> + tmp = pmc_read(pmc, AT91_PMC_PCR); >> + pmc_unlock(pmc); >> + >> + gck->parent_id = (tmp & AT91_PMC_PCR_GCKCSS_MASK) >> + >> AT91_PMC_PCR_GCKCSS_OFFSET; >> + /* >> + * make sure that what we read in hardware is coherent with >> + * what we've just probed >> + */ >> + if (gck->parent_id >= __clk_get_num_parents(gck->hw.clk)) >> + gck->parent_id = 0; > > Hm, I'm not sure this is correct. Here, you're just faking the > fact that your current parent is the first one in the parent list while > it actually points to the 6th entry. Not only your rate will be false > (the one calculated in ->round_rate()), but you're also changing the > behavior of the clk_set_rate() and clk_set_parent() operation (AFAIR, > if you try to change to the first parent, the core code will think it's > already properly configured and will never call ->set_parent()).
Well, as the values are actually used from the cached local structure all the way to the "enable" function, I suspect it won't break the core behavior. And making sure that this clock is not enabled before Linux is run makes this change work.
But I admit it is somehow weird, as a workaround :-\
> This leaves 2 solutions here: > - implement the missing clk driver and add an entry in the parent > list
Yes, I'll do this.
> - select the 1st parent clk (I mean, change the register value) if the > hardware points to the 6th one.
This is not safer than what I proposed hereunder.
So, I remove this change in the v4 and send you a v5 that reverts this modification and adds a WARN_ON the condition, to ease debugging...
Bye, -- Nicolas Ferre
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