Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 25 Feb 2021 21:08:58 +0100 | Subject | Re: [PATCH] coresight: etm4x: work around clang-12+ build failure |
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On Thu, Feb 25, 2021 at 5:45 PM Mathieu Poirier <mathieu.poirier@linaro.org> wrote: > On Thu, Feb 25, 2021 at 10:42:58AM +0100, Arnd Bergmann wrote: > > index 15016f757828..4cccf874a602 100644 > > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > > @@ -691,13 +691,13 @@ static void etm4_disable_hw(void *info) > > "timeout while waiting for PM stable Trace Status\n"); > > > > /* read the status of the single shot comparators */ > > - for (i = 0; i < drvdata->nr_ss_cmp; i++) { > > + for (i = 0; i < min_t(u32, drvdata->nr_ss_cmp, ETM_MAX_SS_CMP); i++) { > > config->ss_status[i] = > > etm4x_relaxed_read32(csa, TRCSSCSRn(i)); > > } > > > > /* read back the current counter values */ > > - for (i = 0; i < drvdata->nr_cntr; i++) { > > + for (i = 0; i < min_t(u32, drvdata->nr_cntr, ETMv4_MAX_CNTR); i++) { > > This patch will work and I'd be happy to apply it if this was the only instance, > but there are dozens of places in the coresight drivers where such patterns are > used. Why are those not flagged as well? And shouldn't the real fix be with > clang?
This is the only one I see in randconfig build tests. In fact I only actually see the second one of the two causing problems, but it seemed silly to change only one of them. I had not noticed the other similar loops that use etm4x_read32() instead of etm4x_relaxed_read32().
I first suspected that the memory clobber in __iormb() prevents the compiler from running into the same problem there, but changing all etm4x_read32() to etm4x_relaxed_read32() did not make it show up in other places either.
While I expect this will be fixed in mainline clang, the workaround should be harmless and let us use the existing releases as well.
Arnd
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