Unverified Commit 0327f0b8 authored May 15, 2020 by Serge Semin Committed by Mark Brown May 15, 2020

spi: dw: Clear DMAC register when done or stopped



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 <Georgy.Vlasov@baikalelectronics.ru>
Signed-off-by: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200515104758.6934-4-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Mark Brown <broonie@kernel.org>

parent 77810d48

drivers/spi/spi-dw-mid.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -106,6 +106,8 @@ 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)
		@@ -152,6 +154,8 @@ 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);
		}

		@@ -199,6 +203,8 @@ 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);
		}

		@@ -292,6 +298,8 @@ 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 mfld_dma_ops = {

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