[PATCH AUTOSEL 4.14 13/14] spi: lantiq: fix: Rx overflow error in full duplex mode

Sasha Levin
2020-08-08T23:41:34Z

From: Dilip Kota <eswara.kota@linux.intel.com>

[ Upstream commit 661ccf2b3f1360be50242726f7c26ced6a9e7d52 ]

In full duplex mode, rx overflow error is observed. To overcome the error,
wait until the complete data got received and proceed further.

Fixes: 17f84b793c01 ("spi: lantiq-ssc: add support for Lantiq SSC SPI controller")
Signed-off-by: Dilip Kota <eswara.kota@linux.intel.com>
Link: https://lore.kernel.org/r/efb650b0faa49a00788c4e0ca8ef7196bdba851d.1594957019.git.eswara.kota@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-lantiq-ssc.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/spi/spi-lantiq-ssc.c b/drivers/spi/spi-lantiq-ssc.c
index d5976615d924b..dc740b5f720ba 100644
--- a/drivers/spi/spi-lantiq-ssc.c
+++ b/drivers/spi/spi-lantiq-ssc.c
@@ -187,6 +187,7 @@ struct lantiq_ssc_spi {
unsigned int tx_fifo_size;
unsigned int rx_fifo_size;
unsigned int base_cs;
+ unsigned int fdx_tx_level;
};

static u32 lantiq_ssc_readl(const struct lantiq_ssc_spi *spi, u32 reg)
@@ -484,6 +485,7 @@ static void tx_fifo_write(struct lantiq_ssc_spi *spi)
u32 data;
unsigned int tx_free = tx_fifo_free(spi);

+ spi->fdx_tx_level = 0;
while (spi->tx_todo && tx_free) {
switch (spi->bits_per_word) {
case 2 ... 8:
@@ -512,6 +514,7 @@ static void tx_fifo_write(struct lantiq_ssc_spi *spi)

lantiq_ssc_writel(spi, data, LTQ_SPI_TB);
tx_free--;
+ spi->fdx_tx_level++;
}
}

@@ -523,6 +526,13 @@ static void rx_fifo_read_full_duplex(struct lantiq_ssc_spi *spi)
u32 data;
unsigned int rx_fill = rx_fifo_level(spi);

+ /*
+ * Wait until all expected data to be shifted in.
+ * Otherwise, rx overrun may occur.
+ */
+ while (rx_fill != spi->fdx_tx_level)
+ rx_fill = rx_fifo_level(spi);
+
while (rx_fill) {
data = lantiq_ssc_readl(spi, LTQ_SPI_RB);

--
2.25.1