From: Ian Arkver <ian.arkver.dev@gmail.com>
To: Sakari Ailus <sakari.ailus@iki.fi>, Nicholas Mc Guire <hofrat@osadl.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
Sylwester Nawrocki <s.nawrocki@samsung.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
Hans Verkuil <hans.verkuil@cisco.com>,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] [media] s5k6aa: set usleep_range greater 0
Date: Tue, 13 Dec 2016 10:10:51 +0000 [thread overview]
Message-ID: <ce9f2ee0-c0d3-2eb4-a733-b108d12b43fb@gmail.com> (raw)
In-Reply-To: <20161213094346.GW16630@valkosipuli.retiisi.org.uk>
On 13/12/16 09:43, Sakari Ailus wrote:
> Hi Nicholas,
>
> On Tue, Dec 13, 2016 at 02:58:02AM +0100, Nicholas Mc Guire wrote:
>> As this is not in atomic context and it does not seem like a critical
>> timing setting a range of 1ms allows the timer subsystem to optimize
>> the hrtimer here.
> I'd suggest not to. These delays are often directly visible to the user in
> use cases where attention is indeed paid to milliseconds.
>
> The same applies to register accesses. An delay of 0 to 100 µs isn't much as
> such, but when you multiply that with the number of accesses it begins to
> add up.
>
Data sheet for this device [1] says STBYN deassertion to RSTN
deassertion should be >50us, though this is actually referenced to MCLK
startup. See Figure 36, Power-Up Sequence, page 42.
I think the usleep range here could be greatly reduced and opened up to
allow hr timer tweaks if desired.
[1] http://www.bdtic.com/DataSheet/SAMSUNG/S5K6AAFX13.pdf
Regards,
Ian
next prev parent reply other threads:[~2016-12-13 10:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20161213015743epcas3p19867fa74e5ffe2974364d317d9b494f6@epcas3p1.samsung.com>
2016-12-13 1:58 ` [PATCH RFC] [media] s5k6aa: set usleep_range greater 0 Nicholas Mc Guire
2016-12-13 9:43 ` Sakari Ailus
2016-12-13 10:10 ` Ian Arkver [this message]
2016-12-13 10:54 ` Sakari Ailus
2016-12-13 12:38 ` Sylwester Nawrocki
2016-12-13 14:10 ` Laurent Pinchart
2016-12-13 14:53 ` Sylwester Nawrocki
2016-12-15 1:14 ` Nicholas Mc Guire
2016-12-15 17:45 ` Sylwester Nawrocki
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