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From: Peter Korsgaard <peter@korsgaard.com>
To: Federico Vaga <federico.vaga@cern.ch>
Cc: Peter Korsgaard <jacmet@sunsite.dk>,
	linux-i2c <linux-i2c@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] i2c:ocores: add polling interface
Date: Mon, 29 Oct 2018 14:04:13 +0100	[thread overview]
Message-ID: <87muqwzyya.fsf@dell.be.48ers.dk> (raw)
In-Reply-To: <5352289.A0jT2G1FDH@pcbe13614> (Federico Vaga's message of "Mon, 29 Oct 2018 09:50:15 +0100")

>>>>> "Federico" == Federico Vaga <federico.vaga@cern.ch> 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

  reply	other threads:[~2018-10-29 13:04 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-25 16:13 i2c:ocores: fixes and polling mechanism Federico Vaga
2018-06-25 16:13 ` [PATCH 1/3] i2c:ocores: stop transfer on timeout Federico Vaga
2018-10-21 14:10   ` Peter Korsgaard
2018-10-24 14:51     ` Federico Vaga
2018-10-26 17:46       ` Peter Korsgaard
2018-10-25  7:42     ` Federico Vaga
2018-06-25 16:13 ` [PATCH 2/3] i2c:ocores: do not handle IRQ if IF is not set Federico Vaga
2018-10-21 14:12   ` Peter Korsgaard
2018-10-29  8:53     ` Wolfram Sang
2018-10-29 14:27       ` Federico Vaga
2018-06-25 16:13 ` [PATCH 3/3] i2c:ocores: add polling interface Federico Vaga
2018-10-21 14:39   ` Peter Korsgaard
2018-10-24  9:51     ` Federico Vaga
2018-10-26 17:45       ` Peter Korsgaard
2018-10-29  8:50         ` Federico Vaga
2018-10-29 13:04           ` Peter Korsgaard [this message]
2018-10-29 13:11             ` Federico Vaga
2018-10-25  7:47     ` Federico Vaga
2018-08-11 17:13 ` i2c:ocores: fixes and polling mechanism Federico Vaga
2018-08-12 15:34   ` Wolfram Sang
2018-08-22 16:16     ` Peter Korsgaard
2018-09-17 16:42       ` Wolfram Sang
2018-09-19  5:15         ` Peter Korsgaard
2018-09-19  6:51           ` Wolfram Sang

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