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author | HyeonSeung Jang <hs8848.jang@samsung.com> | 2006-10-04 15:26:13 (GMT) |
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committer | Paul Mackerras <paulus@samba.org> | 2006-10-04 23:21:01 (GMT) |
commit | 28347bce8a837258e737873a55d31f2f424a6ea6 (patch) | |
tree | 4d19e9abee0ad539ee4a1e1c6877f71e7617612e /arch/powerpc/platforms/cell/spufs/switch.c | |
parent | a68cf983f635930ea35f9e96b27d96598550dea0 (diff) | |
download | linux-fsl-qoriq-28347bce8a837258e737873a55d31f2f424a6ea6.tar.xz |
[POWERPC] spufs: fix context switch during page fault
For better explanation, I break down the page fault handling into steps:
1) There is a page fault caused by DMA operation initiated by SPU and
DMA is suspended.
2) The interrupt handler 'spu_irq_class_1()/__spu_trap_data_map()' is
called and it just wakes up the sleeping spe-manager thread.
3) by PPE scheduler, the corresponding bottom half,
spu_irq_class_1_bottom() is called in process context and DMA is
restarted.
There can be a quite large time gap between 2) and 3) and I found
the following problem:
Between 2) and 3) If the context becomes unbound, 3) is not executed
because when the spe-manager thread is awaken, the context is already
saved. (This situation can happen, for example, when a high priority spe
thread newly started in that time gap)
But the actual problem is that the corresponding SPU context does not
work even if it is bound again to a SPU.
Besides I can see the following warning in mambo simulator when the
context becomes
unbound(in save_mfc_cmd()), i.e. when unbind() is called for the
context after step 2) before 3) :
'WARNING: 61392752237: SPE2: MFC_CMD_QUEUE channel count of 15 is
inconsistent with number of available DMA queue entries of 16'
After I go through available documents, I found that the problem is
because the suspended DMA is not restarted when it is bound again.
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/platforms/cell/spufs/switch.c')
-rw-r--r-- | arch/powerpc/platforms/cell/spufs/switch.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/cell/spufs/switch.c b/arch/powerpc/platforms/cell/spufs/switch.c index 9d9d82d..0f782ca 100644 --- a/arch/powerpc/platforms/cell/spufs/switch.c +++ b/arch/powerpc/platforms/cell/spufs/switch.c @@ -1779,6 +1779,15 @@ static inline void restore_mfc_cntl(struct spu_state *csa, struct spu *spu) */ out_be64(&priv2->mfc_control_RW, csa->priv2.mfc_control_RW); eieio(); + /* + * FIXME: this is to restart a DMA that we were processing + * before the save. better remember the fault information + * in the csa instead. + */ + if ((csa->priv2.mfc_control_RW & MFC_CNTL_SUSPEND_DMA_QUEUE_MASK)) { + out_be64(&priv2->mfc_control_RW, MFC_CNTL_RESTART_DMA_COMMAND); + eieio(); + } } static inline void enable_user_access(struct spu_state *csa, struct spu *spu) |