If DMAC register is left uncleared any further DMAless transfers may cause the DMAC hardware handshaking interface getting activated. So the next DMA-based Rx/Tx transaction will be started right after the dma_async_issue_pending() method is invoked even if no DMATDLR/DMARDLR conditions are met. This at the same time may cause the Tx/Rx FIFO buffers underrun/overrun. In order to fix this we must clear DMAC register after a current DMA-based transaction is finished.
Co-developed-by: Georgy Vlasov <[email protected]> Signed-off-by: Georgy Vlasov <[email protected]> Signed-off-by: Serge Semin <[email protected]> Acked-by: Mark Brown <[email protected]> Cc: Ramil Zaripov <[email protected]> Cc: Alexey Malahov <[email protected]> --- Changelog v2: - Move the patch to the head of the series so one could be picked up to the stable kernels as a fix. - Clear the DMACR in the DMA exit callback too. Changelog v3: - Rebase on top of the spi/for-5.7. --- drivers/spi/spi-dw-mid.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/spi/spi-dw-mid.c b/drivers/spi/spi-dw-mid.c index 0d86c37e0aeb..6f55a7ae2299 100644 --- a/drivers/spi/spi-dw-mid.c +++ b/drivers/spi/spi-dw-mid.c @@ -86,6 +86,8 @@ static void mid_spi_dma_exit(struct dw_spi *dws) dmaengine_terminate_sync(dws->rxchan); dma_release_channel(dws->rxchan); + + dw_writel(dws, DW_SPI_DMACR, 0); } static irqreturn_t dma_transfer(struct dw_spi *dws) @@ -135,6 +137,8 @@ static void dw_spi_dma_tx_done(void *arg) clear_bit(TX_BUSY, &dws->dma_chan_busy); if (test_bit(RX_BUSY, &dws->dma_chan_busy)) return; + + dw_writel(dws, DW_SPI_DMACR, 0); spi_finalize_current_transfer(dws->master); } @@ -181,6 +185,8 @@ static void dw_spi_dma_rx_done(void *arg) clear_bit(RX_BUSY, &dws->dma_chan_busy); if (test_bit(TX_BUSY, &dws->dma_chan_busy)) return; + + dw_writel(dws, DW_SPI_DMACR, 0); spi_finalize_current_transfer(dws->master); } @@ -273,6 +279,8 @@ static void mid_spi_dma_stop(struct dw_spi *dws) dmaengine_terminate_sync(dws->rxchan); clear_bit(RX_BUSY, &dws->dma_chan_busy); } + + dw_writel(dws, DW_SPI_DMACR, 0); } static const struct dw_spi_dma_ops mid_dma_ops = { -- 2.25.1
