dmaengine: dw-axi-dmac: Wait for runtime resume...#7484
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...before using a channel dma_chan_alloc_chan_resources() called pm_runtime_get(), which only schedules the clock-enabling resume work asynchronously. If callers go on to configure and use the channel's registers immediately, the clocks may not yet be running, causing early register writes (e.g. CH_CFG) to be silently dropped. Later accesses succeed once the clock has come up, leaving the channel enabled but with an invalid configuration, and its completion interrupt never fires. Use pm_runtime_resume_and_get() so the clocks are guaranteed to be enabled before the channel is handed back to the caller. Fixes: 1fe20f1 ("dmaengine: Introduce DW AXI DMAC driver") Signed-off-by: Phil Elwell <phil@raspberrypi.com>
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See: raspberrypi/linux#7500 kernel: staging: vchiq_arm: use one DMA device to map and unmap bulk pagelists See: raspberrypi/linux#7494 kernel: drm/vc4: hdmi: Remove duplicate hotplug helper call See: raspberrypi/linux#7489 kernel: ASoC: hifiberry_studio: change driver name and add support for new soundcards See: raspberrypi/linux#7487 kernel: mmc: Fix MMC request issuing race condition to prevent stall See: raspberrypi/linux#7486 kernel: dmaengine: dw-axi-dmac: Wait for runtime resume before using a channel See: raspberrypi/linux#7484 kernel: overlays: i2c-fan: add compatible for upstream compatibility See: raspberrypi/linux#7483
popcornmix
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See: raspberrypi/linux#7500 kernel: staging: vchiq_arm: use one DMA device to map and unmap bulk pagelists See: raspberrypi/linux#7494 kernel: drm/vc4: hdmi: Remove duplicate hotplug helper call See: raspberrypi/linux#7489 kernel: ASoC: hifiberry_studio: change driver name and add support for new soundcards See: raspberrypi/linux#7487 kernel: mmc: Fix MMC request issuing race condition to prevent stall See: raspberrypi/linux#7486 kernel: dmaengine: dw-axi-dmac: Wait for runtime resume before using a channel See: raspberrypi/linux#7484 kernel: overlays: i2c-fan: add compatible for upstream compatibility See: raspberrypi/linux#7483
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...before using a channel
dma_chan_alloc_chan_resources() called pm_runtime_get(), which only schedules the clock-enabling resume work asynchronously. If callers go on to configure and use the channel's registers immediately, the clocks may not yet be running, causing early register writes (e.g. CH_CFG) to be silently dropped. Later accesses succeed once the clock has come up, leaving the channel enabled but with an invalid configuration, and its completion interrupt never fires.
Use pm_runtime_resume_and_get() so the clocks are guaranteed to be enabled before the channel is handed back to the caller.