From a750b124cfd27bae1a12df22318db5a2083dfb12 Mon Sep 17 00:00:00 2001
From: Martin Sperl <kernel@martin.sperl.org>
Date: Wed, 22 Apr 2015 07:33:03 +0000
Subject: [PATCH] spi: bcm2835: fallback to interrupt for polling timeouts
 exceeding 2 jiffies

The polling mode of the driver is designed for transfers that run
less than 30us - it will only execute under those circumstances.
So it should run comfortably without getting interrupted by the
scheduler.

But there are situations where the raspberry pi is so overloaded
that it can take up to 80 jiffies until the polling thread gets
rescheduled - this has been observed especially under heavy
IO situations.

In such a situation we now fall back to the interrupt handler and
log the situation at debug level.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
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