From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniel.lezcano@linaro.org (Daniel Lezcano) Date: Wed, 16 Dec 2015 10:02:24 +0100 Subject: [PATCH] clocksource/drivers/pistachio: Fix wrong calculated clocksource read value In-Reply-To: <20151216151125.1e91b4f4@xhacker> References: <1448466169-5230-1-git-send-email-jszhang@marvell.com> <56707F32.3030405@linaro.org> <20151216151125.1e91b4f4@xhacker> Message-ID: <567128A0.8060107@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 12/16/2015 08:11 AM, Jisheng Zhang wrote: > Dear Daniel, > > On Tue, 15 Dec 2015 21:59:30 +0100 Daniel Lezcano wrote: > >> On 11/25/2015 04:42 PM, Jisheng Zhang wrote: >>> Let's assume the counter value is 0xf000000, the pistachio clocksource >>> read cycles function would return 0xffffffff0fffffff, but it should >>> return 0xfffffff. >>> >>> We fix this issue by calculating bitwise-not counter, then cast to >>> cycle_t. >>> >>> Signed-off-by: Jisheng Zhang >> >> Hi Jisheng, >> >> I tried to reproduce this behavior on x86_64 but without success. >> >> On which architecture did you produce this result ? Do you have a simple >> test program to check with ? > > I have no HW platforms with pistachio, just read the code and run the > following test code in x86_64 and x86_32: > > #include > unsigned long long pistachio_clocksource_read_cycles() > { > unsigned int counter = 0xf000000; > return ~(unsigned long long)counter; > } > int main() > { > printf("%llx\n", pistachio_clocksource_read_cycles()); > return 0; > } Ok, I reproduced it. I had an issue with the signed/unsigned type. That's a good catch ! -- Linaro.org ? Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog