From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756862AbcA2TpE (ORCPT ); Fri, 29 Jan 2016 14:45:04 -0500 Received: from foss.arm.com ([217.140.101.70]:40953 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756757AbcA2TpC (ORCPT ); Fri, 29 Jan 2016 14:45:02 -0500 Subject: Re: [PATCH] clocksource/arm_arch_timer: Enable and verify MMIO access To: Stephen Boyd References: <20160129183051.GO12841@codeaurora.org> Cc: mark.rutland@arm.com, tglx@linutronix.de, daniel.lezcano@linaro.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org From: Robin Murphy Message-ID: <56ABC13B.9080500@arm.com> Date: Fri, 29 Jan 2016 19:44:59 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160129183051.GO12841@codeaurora.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/01/16 18:30, Stephen Boyd wrote: > On 01/29, Robin Murphy wrote: >> So far, we have been blindly assuming that if a memory-mapped timer >> frame exists, then we have access to it. Whilst it's the firmware's >> job to give us non-secure access to frames in the first place, we >> should not rely on it always being generous enough to also configure >> CNTACR if it's not even using those frames itself. > > 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." >> >> 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 >> --- >> 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. >> + >> + if ((cnttidr & CNTTIDR_VIRT(n)) && >> + !(~cntacr & (CNTACR_RWVT | CNTACR_RVCT))) { >> of_node_put(best_frame); >> best_frame = frame; >> arch_timer_mem_use_virtual = true; >> break; >> } >> + >> + if (~cntacr & (CNTACR_RWPT | CNTACR_RPCT)) >> + continue; >> + >> of_node_put(best_frame); >> best_frame = of_node_get(frame); >> } > > Otherwise the patch looks fine and passes some light testing on > qcom devices. 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 > BTW, I'd like to add this patch on top so that we get some info > in /proc/iomem about which frame region is in use. It's about time I educated myself on what all the resource stuff really means, but superficially it seems reasonable, and it certainly makes the expected "2a830000-2a83ffff : arch_mem_timer" show up on my Juno. Thanks, Robin. > ---8<--- > From: Stephen Boyd > Subject: [PATCH] clocksource/arm_arch_timer: Map frame with > of_io_request_and_map() > > Let's use the of_io_request_and_map() API so that the frame > region is protected and shows up in /proc/iomem. > > Signed-off-by: Stephen Boyd > --- > drivers/clocksource/arm_arch_timer.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c > index c88485d489bf..59a08fd4f76a 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -804,7 +804,8 @@ static void __init arch_timer_mem_init(struct device_node *np) > best_frame = of_node_get(frame); > } > > - base = arch_counter_base = of_iomap(best_frame, 0); > + base = arch_counter_base = of_io_request_and_map(best_frame, 0, > + "arch_mem_timer"); > if (!base) { > pr_err("arch_timer: Can't map frame's registers\n"); > goto out; >