Re: [PATCH RFC] [media] s5k6aa: set usleep_range greater 0

[Ian Arkver]

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