On 01/29, Robin Murphy wrote: > On 29/01/16 18:30, Stephen Boyd wrote: > >On 01/29, Robin Murphy wrote: > >Hm, that first sentence is sort of misleading. We've been blindly > >assuming that the firmware has configured CNTACR to have the > >correct bits set for virtual/physical access. We've always relied > >on status = "disabled" to figure out if we can access an entire > >frame or not. > > Yeah, now that I read it back that sentence is nonsense for anything > other than the very specific ideas of "frame" and "exists" that were > passing through my head at some point last week - how about this > instead? > > "So far, we have been blindly assuming that having access to a > memory-mapped timer frame implies that the individual elements of > that frame are already enabled."
Sounds good. > > >> > >>Explicitly enable feature-level access per-frame, and verify that the > >>access we want is really implemented before trying to make use of it. > >> > >>Signed-off-by: Robin Murphy <[email protected]> > >>--- > >> drivers/clocksource/arm_arch_timer.c | 39 > >> ++++++++++++++++++++++++++++-------- > >> 1 file changed, 31 insertions(+), 8 deletions(-) > >> > >>diff --git a/drivers/clocksource/arm_arch_timer.c > >>b/drivers/clocksource/arm_arch_timer.c > >>index c64d543..c88485d 100644 > >>--- a/drivers/clocksource/arm_arch_timer.c > >>+++ b/drivers/clocksource/arm_arch_timer.c > >>@@ -765,20 +772,34 @@ static void __init arch_timer_mem_init(struct > >>device_node *np) > >> */ > >> for_each_available_child_of_node(np, frame) { > >> int n; > >>+ u32 cntacr; > >> > >> if (of_property_read_u32(frame, "frame-number", &n)) { > >> pr_err("arch_timer: Missing frame-number\n"); > >>- of_node_put(best_frame); > >> of_node_put(frame); > >>- return; > >>+ goto out; > >> } > >> > >>- if (cnttidr & CNTTIDR_VIRT(n)) { > >>+ /* Try enabling everything, and see what sticks */ > >>+ cntacr = CNTACR_RFRQ | CNTACR_RWPT | CNTACR_RPCT | > >>+ CNTACR_RWVT | CNTACR_RVOFF | CNTACR_RVCT; > >>+ writel_relaxed(cntacr, cntctlbase + CNTACR(n)); > >>+ cntacr = readl_relaxed(cntctlbase + CNTACR(n)); > >>+ > >>+ if (~cntacr & CNTACR_RFRQ) > >>+ continue; > > > >Do we need this check? If we can't read the frequency we fall > >back to looking for the DT property, so it shouldn't matter if we > >can't read the hardware there. > > I was really just playing safe to start with. If we don't have cause > to care about the difference between not having access vs. not > having a frequency programmed then I'd agree it can probably go. > Yeah I'm mostly worried that we'll break something somewhere because that bit doesn't stick and it's the only frame we can use. Or we can give it a shot and then remove clock-frequency from the dts binding for mmio timers. > > Great, thanks. The Trusted Firmware guys' warning shot has gone > upstream already, if it helps: > > https://github.com/ARM-software/arm-trusted-firmware/commit/01fc3f7300e86b0b672977133c3028d638d0c672 Ah I see. It would be nice if that bug gave a reason why it should be done, instead of just saying it must be this way. O well. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
