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[82.143.95.228]) by smtp.gmail.com with ESMTPSA id a4-v6sm5829154edt.82.2018.10.29.06.04.14 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 29 Oct 2018 06:04:14 -0700 (PDT) Received: from peko by dell.be.48ers.dk with local (Exim 4.89) (envelope-from ) id 1gH7DJ-0004Uf-Og; Mon, 29 Oct 2018 14:04:13 +0100 From: Peter Korsgaard To: Federico Vaga Cc: Peter Korsgaard , linux-i2c , Subject: Re: [PATCH 3/3] i2c:ocores: add polling interface References: <20180625161303.7991-1-federico.vaga@cern.ch> <4222986.LvGMQbjSbS@pcbe13614> <87woq438li.fsf@dell.be.48ers.dk> <5352289.A0jT2G1FDH@pcbe13614> Date: Mon, 29 Oct 2018 14:04:13 +0100 In-Reply-To: <5352289.A0jT2G1FDH@pcbe13614> (Federico Vaga's message of "Mon, 29 Oct 2018 09:50:15 +0100") Message-ID: <87muqwzyya.fsf@dell.be.48ers.dk> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "Federico" == Federico Vaga writes: Hi, >> >> Where does this 10 come from? >> > >> > It's true, it's just a random number. It can be zero as well, and we ask >> > the system to just sleep for that amount of time. >> > >> > (1) usleep_range(sleep_min, sleep_min); >> >> Or just usleep(sleep_min); > This does not exist as far as I know; the alternative is an active wait with > udelay. But then, it is not that different from just start polling TIP or BUSY > flags. Ahh yes. > I think that something like this could be better > (2) usleep_range(sleep_min, sleep_min * XXX); > But. > Since it is better to make this patch ready for xfer_irqless, then I will > definitively go for udelay(). The reason is that, xfer_irqless may run in > atomic context where we can't sleep at all. Great! BTW I noticed that your sleep_min calculation looked odd: int sleep_min = (8/i2c->bus_clock_khz) * 1000; /* us for 8bits bus_clock_khz almost certainly will be bigger than 8 (E.G. likely 100KHz), so the above set sleep_min to 0. Please move the * 1000 before the division. -- Bye, Peter Korsgaard