linux-kernel - [PATCH] spi: atmel: init FIFOs before spi enable

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Message-ID: <1519727107-5821-1-git-send-email-eugen.hristev@microchip.com>
Date:   Tue, 27 Feb 2018 12:25:07 +0200
From:   Eugen Hristev <eugen.hristev@...rochip.com>
To:     <nicolas.ferre@...rochip.com>, <broonie@...nel.org>,
        <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     Eugen Hristev <eugen.hristev@...rochip.com>
Subject: [PATCH] spi: atmel: init FIFOs before spi enable

The datasheet recommends initializing FIFOs before
SPI enable. If we do not do it like this, there may be
a strange behavior. We noticed that DMA does not work properly
with FIFOs if we do not clear them beforehand or enable them
before SPIEN.

Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
---
 drivers/spi/spi-atmel.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 6694709..0478758 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -1489,6 +1489,11 @@ static void atmel_spi_init(struct atmel_spi *as)
 {
 	spi_writel(as, CR, SPI_BIT(SWRST));
 	spi_writel(as, CR, SPI_BIT(SWRST)); /* AT91SAM9263 Rev B workaround */
+
+	/* It is recommended to enable FIFOs first thing after reset */
+	if (as->fifo_size)
+		spi_writel(as, CR, SPI_BIT(FIFOEN));
+
 	if (as->caps.has_wdrbt) {
 		spi_writel(as, MR, SPI_BIT(WDRBT) | SPI_BIT(MODFDIS)
 				| SPI_BIT(MSTR));
@@ -1499,9 +1504,6 @@ static void atmel_spi_init(struct atmel_spi *as)
 	if (as->use_pdc)
 		spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
 	spi_writel(as, CR, SPI_BIT(SPIEN));
-
-	if (as->fifo_size)
-		spi_writel(as, CR, SPI_BIT(FIFOEN));
 }
 
 static int atmel_spi_probe(struct platform_device *pdev)
-- 
2.7.4