On 10/27/2016 12:34 PM, Marek Szyprowski wrote:
ASoC Samsung sub-drivers tried to get access to their DMA engine controllers as a last step in driver probe. If a DMA engine was not available yet, samsung_asoc_dma_platform_register() function ended in -EPROBE_DEFER, but the driver already registered its component to ASoC core. This patch moves samsung_asoc_dma_platform_register() call before registering any components, to the common place, where driver was gathering all needed resources.
In case of Samsung Exynos i2s driver the issue was even worse. The driver managed already to register its secondary DAI platform device before even getting the DMA engine access. That together with -EPROBE_DEFER error code from samsung_i2s_probe() immediately triggered another round of deferred probe retry and in turn endless loop of driver probing.
This patch fixes broken boot on Odroid XU3 and other Exynos5422-based boards.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com
Reviewed-by: Sylwester Nawrocki s.nawrocki@samsung.com
It's worth to note that the endless re-probing loop happens randomly, not on every boot. And the issue got uncovered by a commit which seems to be slightly changing scheduling of work on the main probe deferral workqueue and deferral of the amba devices [1], i.e. after this commit all probe deferral jobs are scheduled to a single system_wq workqueue. It seems concurrency change after the patch was significant enough to make deferred probing of one device to starve deferred probing of other device in that case.
[1] commit 2c507e464f791327c94d17a0137f00b4717744fc "device core: Remove deprecated create_singlethread_workqueue"