linux-kernel - [PATCH 3.19 65/75] spi: dw-mid: clear BUSY flag fist and test other one

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Date:	Fri, 10 Apr 2015 15:19:31 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Mark Brown <broonie@...nel.org>
Subject: [PATCH 3.19 65/75] spi: dw-mid: clear BUSY flag fist and test other one

3.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

commit 854d2f241d71f6ca08ccde30e6c7c2e403363e52 upstream.

The logic of DMA completion is broken now since test_and_clear_bit() never
returns the other bit is set. It means condition are always false and we have
spi_finalize_current_transfer() called per each DMA completion which is wrong.

The patch fixes logic by clearing BUSY bit first and then check for the other
one.

Fixes: 30c8eb52cc4a (spi: dw-mid: split rx and tx callbacks when DMA)
Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/spi/spi-dw-mid.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/spi/spi-dw-mid.c
+++ b/drivers/spi/spi-dw-mid.c
@@ -108,7 +108,8 @@ static void dw_spi_dma_tx_done(void *arg
 {
 	struct dw_spi *dws = arg;
 
-	if (test_and_clear_bit(TX_BUSY, &dws->dma_chan_busy) & BIT(RX_BUSY))
+	clear_bit(TX_BUSY, &dws->dma_chan_busy);
+	if (test_bit(RX_BUSY, &dws->dma_chan_busy))
 		return;
 	dw_spi_xfer_done(dws);
 }
@@ -156,7 +157,8 @@ static void dw_spi_dma_rx_done(void *arg
 {
 	struct dw_spi *dws = arg;
 
-	if (test_and_clear_bit(RX_BUSY, &dws->dma_chan_busy) & BIT(TX_BUSY))
+	clear_bit(RX_BUSY, &dws->dma_chan_busy);
+	if (test_bit(TX_BUSY, &dws->dma_chan_busy))
 		return;
 	dw_spi_xfer_done(dws);
 }


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