linux-kernel - [RFC PATCH 08/10] spi: mxic: Fix the transmit path

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Message-Id: <20211008162228.1753083-9-miquel.raynal@bootlin.com>
Date:   Fri,  8 Oct 2021 18:22:26 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tudor Ambarus <Tudor.Ambarus@...rochip.com>,
        <linux-mtd@...ts.infradead.org>
Cc:     Rob Herring <robh+dt@...nel.org>, Mark Brown <broonie@...nel.org>,
        Xiangsheng Hou <Xiangsheng.Hou@...iatek.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        devicetree@...r.kernel.org, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org, jaimeliao@...c.com.tw,
        juliensu@...c.com.tw,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        stable@...r.kernel.org, Mason Yang <masonccyang@...c.com.tw>
Subject: [RFC PATCH 08/10] spi: mxic: Fix the transmit path

By working with external hardware ECC engines, we figured out that
Under certain circumstances, it is needed for the SPI controller to
check INT_TX_EMPTY and INT_RX_NOT_EMPTY in both receive and transmit
path (not only in the receive path). The delay penalty being
negligible, move this code in the common path.

Fixes: b942d80b0a39 ("spi: Add MXIC controller driver")
Cc: stable@...r.kernel.org
Suggested-by: Mason Yang <masonccyang@...c.com.tw>
Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 drivers/spi/spi-mxic.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/spi/spi-mxic.c b/drivers/spi/spi-mxic.c
index 96b418293bf2..4fb19e6f94b0 100644
--- a/drivers/spi/spi-mxic.c
+++ b/drivers/spi/spi-mxic.c
@@ -304,25 +304,21 @@ static int mxic_spi_data_xfer(struct mxic_spi *mxic, const void *txbuf,
 
 		writel(data, mxic->regs + TXD(nbytes % 4));
 
+		ret = readl_poll_timeout(mxic->regs + INT_STS, sts,
+					 sts & INT_TX_EMPTY, 0, USEC_PER_SEC);
+		if (ret)
+			return ret;
+
+		ret = readl_poll_timeout(mxic->regs + INT_STS, sts,
+					 sts & INT_RX_NOT_EMPTY, 0,
+					 USEC_PER_SEC);
+		if (ret)
+			return ret;
+
+		data = readl(mxic->regs + RXD);
 		if (rxbuf) {
-			ret = readl_poll_timeout(mxic->regs + INT_STS, sts,
-						 sts & INT_TX_EMPTY, 0,
-						 USEC_PER_SEC);
-			if (ret)
-				return ret;
-
-			ret = readl_poll_timeout(mxic->regs + INT_STS, sts,
-						 sts & INT_RX_NOT_EMPTY, 0,
-						 USEC_PER_SEC);
-			if (ret)
-				return ret;
-
-			data = readl(mxic->regs + RXD);
 			data >>= (8 * (4 - nbytes));
 			memcpy(rxbuf + pos, &data, nbytes);
-			WARN_ON(readl(mxic->regs + INT_STS) & INT_RX_NOT_EMPTY);
-		} else {
-			readl(mxic->regs + RXD);
 		}
 		WARN_ON(readl(mxic->regs + INT_STS) & INT_RX_NOT_EMPTY);
 
-- 
2.27.0