[PATCH v2 09/21] ARM: pxa: magician: Add OV9640 camera support

On Fri, 21 Aug 2015, Arnd Bergmann wrote:

On Friday 21 August 2015 00:39:30 Petr Cvek wrote:

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Dne 20.8.2015 v 22:26 Arnd Bergmann napsal(a):

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On Thursday 20 August 2015 21:48:20 Robert Jarzmik wrote:

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Petr Cvek [off-list ref] writes:

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+     mdelay(3);

Okay, there are several mdelay(3) in this file.

Could you please test if removing these mdelays prevents the camera from working
? If not, I'd like to have them removed.

FWIW, it might be possible to replace some of them with msleep() calls,
potentially after replacing spinlocks with mutexes where necessary.

      Arnd

Datasheet says:

        tS:RESET        Setting time after software/hardware reset      1 ms

So at least one ~1 ms should be left there. Are msleep less than 20ms valid? 

(checkpatch: msleep < 20ms  can sleep for up to 20ms)

On most kernels, an msleep(1) will sleep somewhere between 1 and 3 milliseconds
(but could be much longer), while an mdelay(1) tries to sleep around one
millisecond, more or less.

If high-res timers are available I'd suggest using usleep_range()
instead.  By providing suitably divergent values usleep_range
de-restricts the kernel, allowing the scheduler to bundle your
wake-up along with others.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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