Date: Fri, 24 Sep 2021 19:19:41 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Emmanuel Vadot <manu@bidouilliste.com> Cc: arm@FreeBSD.org, Emmanuel Vadot <manu@freebsd.org> Subject: Re: rk_gpio: high latency switching between input / output Message-ID: <5b3a2e6b-dd1f-59a5-d372-6e9ebe12200d@FreeBSD.org> In-Reply-To: <20210923091821.dd92732fa44d30f94a9415b1@bidouilliste.com> References: <4472ded5-1815-e7c0-0238-efd6935062e0@FreeBSD.org> <20210923091821.dd92732fa44d30f94a9415b1@bidouilliste.com>
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On 23/09/2021 10:18, Emmanuel Vadot wrote: > > I've made some tests on my rock64 board. > The program I used [1] is, I think, the worst possible scenario that > can happen as it : > - Set the pin to output > - Toggle the pin > - Set the pin to input > - Read the pin > - Set the pin to output > > With it I get a ~30khz signal produced on the pin. > > I did some change to rk_gpio [2], those changes are : > > - Cache the pin info (gpio or not) and flags (pullup/pulldown) > - Remove useless reads for the pin direction and value when we're > setting or toggling the pin (so output mode only). > > With this and the same program I manage to have a ~50khz signal output > on the pin. > I'm not sure I can get higher result for now. > > All test where done on main (c96da199458) with GENERIC kernel. > Obviously you will have better result for kernel operation but I > choose to do userland to have the worst case possible. > > Let me know if this helps you in your case, otherwise I'll hookup some > 1wire temp sensors and try to make them work while the scope is still > plugged on the board. > > 1: https://people.freebsd.org/~manu/rk_gpio/gpio_test.c > 2: https://people.freebsd.org/~manu/rk_gpio/0001-arm64-rockchip-rk_gpio-Improve-mode-switching.patch > Thank you very much! 1-wire works reliably for me with your patch. Hope to see it committed soon. -- Andriy Gapon
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