Dear Tobias, On 2016-09-24 20:58, Tobias Jakobi wrote:
The commit b05984e21a7e000bf5074ace00d7a574944b2c16 broke operation of the G2D. After this commit the following happens. - exynos_g2d_exec_ioctl() prepares a runqueue node and calls g2d_exec_runqueue() - g2d_exec_runqueue() calls g2d_dma_start() which gets runtime PM sync - runtime PM calls g2d_runtime_resume() - g2d_runtime_resume() calls g2d_exec_runqueue() Luckily for us this doesn't really loop, but creates a mutex lockup, which the kernel even predicts. Anyway, we fix this by reintroducing dedicated sleep operations again, and only letting runtime PM control the gate clock. This is not enough to fix the issue though. - We switch runtime PM to autosuspend. Currently clocks get disabled, and then re-enabled again in the runqueue worker when a node is completed and the next is started. With the upcoming introduction of IOMMU runtime PM this situations gets worse, since now also the IOMMU goes through a disable/enable cycle before the next node is started. - We consolidate all runtime PM management to the runqueue worker. - We introduce g2d_wait_finish() which waits until the currently processed runqueue node is finished. If this takes too long, the engine is forcibly reset. This is necessary to properly close the driver in case the engine should hang with read/write access to some area of memory. In this situation we can't properly unmap GEM/userptr objects, since this might create a pagefault. - Sleep suspend issues a suspend of the runqueue and then calls g2d_wait_finish(), which returns the engine in the idle state. The current runqueue node gets completed, all other queued nodes stay in the queue. There is no hardware state that needs to be retained. - Sleep resume just pokes the runqueue worker, which, should something be in queue, continues its work, or just exits.
IMHO there is too much done in one patch. It would be much easier to understand it if the changes are split into 2 parts: restoring dedicated speep callbacks and their integration with runqueue worker and addition of autosuspend-based runtime pm.
Changes in v2: - disable autosuspend mode again in g2d_remove() - only get sync in g2d_runqueue_worker() if there is node in the queue left Changes in v3: - actually delete node in g2d_remove_runqueue_nodes() Signed-off-by: Tobias Jakobi <tjakobi@xxxxxxxxxxxxxxxxxxxxx>
[...] Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
