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generated by cgit v1.2.3-54-g00ecf (git 2.39.0) at 2025-01-27 06:36:42 +0000
PID: 14 at drivers/dma/cppi41.c:452 push_desc_queue+0x94/0x9c [cppi41] ... Unable to handle kernel NULL pointer dereference at virtual address 00000104 pgd = c0004000 [00000104] *pgd=00000000 Internal error: Oops: 805 [#1] SMP ARM ... [<bf0d92cc>] (cppi41_runtime_resume [cppi41]) from [<c0589838>] (__rpm_callback+0xc0/0x214) [<c0589838>] (__rpm_callback) from [<c05899ac>] (rpm_callback+0x20/0x80) [<c05899ac>] (rpm_callback) from [<c0589460>] (rpm_resume+0x504/0x78c) [<c0589460>] (rpm_resume) from [<c058a1a0>] (pm_runtime_work+0x60/0xa8) [<c058a1a0>] (pm_runtime_work) from [<c0156120>] (process_one_work+0x2b4/0x808) This is because of a race with runtime PM and cppi41_dma_issue_pending() as reported by Alexandre Bailon <abailon@baylibre.com> in earlier set of patches. Based on mailing list discussions we however came to the conclusion that a different fix from Alexandre's fix is needed in order to guarantee that DMA is really active when we try to use it. To fix the issue, we need to add a driver specific flag as we otherwise can have -EINPROGRESS state set by runtime PM and can't rely on pm_runtime_active() to tell us when we can use the DMA. And we need to make sure the DMA transfers get triggered in the queued order. So let's always queue the transfers, then flush the queue from both cppi41_dma_issue_pending() and cppi41_runtime_resume() as suggested by Grygorii Strashko <grygorii.strashko@ti.com> in an earlier example patch. For reference, this is also documented in Documentation/power/runtime_pm.txt in the example at the end of the file as pointed out by Grygorii Strashko <grygorii.strashko@ti.com>. Based on earlier patches from Alexandre Bailon <abailon@baylibre.com> and Grygorii Strashko <grygorii.strashko@ti.com> modified based on testing and what was discussed on the mailing lists. Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support") Cc: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Bin Liu <b-liu@ti.com> Cc: Grygorii Strashko <grygorii.strashko@ti.com> Cc: Kevin Hilman <khilman@baylibre.com> Cc: Patrick Titiano <ptitiano@baylibre.com> Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> Reported-by: Alexandre Bailon <abailon@baylibre.com> Signed-off-by: Tony Lindgren <tony@atomide.com> Tested-by: Bin Liu <b-liu@ti.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
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