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6a3b45ada9
MIXER on Exynos5 SoCs uses different synchronisation method than Exynos4 to update internal state (shadow registers). Apparently the driver implements it incorrectly. The rule should be as follows: - do not request updating registers until previous request was finished, ie. MXR_CFG_LAYER_UPDATE_COUNT must be 0. - before setting registers synchronisation on VSYNC should be turned off, ie. MXR_STATUS_SYNC_ENABLE should be reset, - after finishing MXR_STATUS_SYNC_ENABLE should be set again. The patch hopefully implements it correctly. Below sample kernel log from page fault caused by the bug: [ 25.670038] exynos-sysmmu 14650000.sysmmu: 14450000.mixer: PAGE FAULT occurred at 0x2247b800 [ 25.677888] ------------[ cut here ]------------ [ 25.682164] kernel BUG at ../drivers/iommu/exynos-iommu.c:450! [ 25.687971] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM [ 25.693778] Modules linked in: [ 25.696816] CPU: 5 PID: 1553 Comm: fb-release_test Not tainted 5.0.0-rc7-01157-g5f86b1566bdd #136 [ 25.705646] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) [ 25.711710] PC is at exynos_sysmmu_irq+0x1c0/0x264 [ 25.716470] LR is at lock_is_held_type+0x44/0x64 v2: added missing MXR_CFG_LAYER_UPDATE bit setting in mixer_enable_sync Reported-by: Marian Mihailescu <mihailescu2m@gmail.com> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com> Signed-off-by: Inki Dae <inki.dae@samsung.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.