From mboxrd@z Thu Jan 1 00:00:00 1970 From: kernel@martin.sperl.org Subject: [PATCH V2 3/9] spi: bcm2835aux: use BCM2835_AUX_SPI_STAT_RX_LVL Date: Sun, 24 Mar 2019 17:49:56 +0000 Message-ID: <20190324175002.28969-4-kernel@martin.sperl.org> References: <20190324175002.28969-1-kernel@martin.sperl.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Martin Sperl To: Mark Brown , Eric Anholt , Stefan Wahren , Hubert Denkmair , linux-spi@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org Return-path: In-Reply-To: <20190324175002.28969-1-kernel@martin.sperl.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: linux-spi.vger.kernel.org From: Martin Sperl On long running tests with a mcp2517fd can controller it showed that on rare occations the data read shows corruptions for longer spi transfers. Example of a 22 byte transfer: expected (as captured on logic analyzer): FF FF 78 00 00 00 08 06 00 00 91 20 77 56 84 85 86 87 88 89 8a 8b read by the driver: FF FF 78 00 00 00 08 06 00 00 91 20 77 56 84 88 89 8a 00 00 8b 9b To fix this use BCM2835_AUX_SPI_STAT_RX_LVL to determine when we may read data from the fifo reliably without any corruption. Surprisingly the only values ever empirically read in BCM2835_AUX_SPI_STAT_RX_LVL are 0x00, 0x10, 0x20 and 0x30. So whenever the mask is not 0 we can read from the fifo in a safe manner. The patch has now been tested intensively and we are no longer able to reproduce the "RX" issue any longer. Fixes: 1ea29b39f4c812ece2f936065a0a3d6fe44a263e Reported-by: Hubert Denkmair Signed-off-by: Martin Sperl --- drivers/spi/spi-bcm2835aux.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c index 0838dbda57c7..d9e62f717a45 100644 --- a/drivers/spi/spi-bcm2835aux.c +++ b/drivers/spi/spi-bcm2835aux.c @@ -180,12 +180,12 @@ static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs) static void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs) { + u32 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT); + /* check if we have data to read */ - while (bs->rx_len && - (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) & - BCM2835_AUX_SPI_STAT_RX_EMPTY))) { + for (; bs->rx_len && (stat & BCM2835_AUX_SPI_STAT_RX_LVL); + stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT)) bcm2835aux_rd_fifo(bs); - } /* check if we have data to write */ while (bs->tx_len && -- 2.11.0