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    spi: bcm2835: Synchronize with callback on DMA termination · 2527704d
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    Commit b36f09c3 ("dmaengine: Add transfer termination
    synchronization support") deprecated dmaengine_terminate_all() in favor
    of dmaengine_terminate_sync() and dmaengine_terminate_async() to avoid
    freeing resources used by the DMA callback before its execution has
    concluded.
    
    Commit de92436a
    
     ("dmaengine: bcm2835-dma: Use vchan_terminate_vdesc()
    instead of desc_free") amended the BCM2835 DMA driver with an
    implementation of ->device_synchronize(), which is a prerequisite for
    dmaengine_terminate_sync().  Thus, clients of the DMA driver (such as
    the BCM2835 SPI driver) may now be converted to the new API.
    
    It is generally desirable to use the _sync() variant except in atomic
    context.  There is only a single occurrence where the BCM2835 SPI driver
    calls dmaengine_terminate_all() in atomic context and that is in
    bcm2835_spi_dma_done() (the RX DMA channel's callback) to terminate the
    TX DMA channel.  The TX DMA channel doesn't have a callback (yet), hence
    it is safe to use the _async() variant there.
    
    Signed-off-by: default avatarLukas Wunner <lukas@wunner.de>
    Cc: Frank Pavlic <f.pavlic@kunbus.de>
    Cc: Martin Sperl <kernel@martin.sperl.org>
    Cc: Noralf Trønnes <noralf@tronnes.org>
    Cc: Vinod Koul <vkoul@kernel.org>
    Signed-off-by: default avatarMark Brown <broonie@kernel.org>
    2527704d