linux-kernel - [PATCH 8/9] mtd: fsl-quadspi: disable AHB buffer prefetch

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Message-ID: <1460605855-6689-9-git-send-email-B56489@freescale.com>
Date:	Thu, 14 Apr 2016 11:50:54 +0800
From:	Yunhui Cui <B56489@...escale.com>
To:	<dwmw2@...radead.org>, <computersforpeace@...il.com>,
	<han.xu@...escale.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
	<linux-arm-kernel@...ts.infradead.org>, <yao.yuan@....com>,
	Yunhui Cui <yunhui.cui@....com>
Subject: [PATCH 8/9] mtd: fsl-quadspi: disable AHB buffer prefetch

From: Yunhui Cui <yunhui.cui@....com>

A-009282: QuadSPI: QuadSPI data pre-fetch can result in incorrect data
Affects: QuadSPI
Description: With AHB buffer prefetch enabled, the QuadSPI may return
incorrect data on the AHB
interface. The buffer pre-fetch is enabled if the fetch size as
configured either in the LUT or in
the BUFxCR register is greater than 8 bytes.
Impact: Only 64 bit read allowed.
Workaround: Keep the read data size to 64 bits (8 Bytes), which disables
the prefetch on the AHB buffer,
and prevents this issue from occurring.

Signed-off-by: Yunhui Cui <yunhui.cui@....com>
---
 drivers/mtd/spi-nor/fsl-quadspi.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c b/drivers/mtd/spi-nor/fsl-quadspi.c
index fea18b6..d9f3e50 100644
--- a/drivers/mtd/spi-nor/fsl-quadspi.c
+++ b/drivers/mtd/spi-nor/fsl-quadspi.c
@@ -752,19 +752,36 @@ static void fsl_qspi_init_abh_read(struct fsl_qspi *q)
 {
 	void __iomem *base = q->iobase;
 	int seqid;
+	const struct fsl_qspi_devtype_data *devtype_data = q->devtype_data;
 
 	/* AHB configuration for access buffer 0/1/2 .*/
 	qspi_writel(q, QUADSPI_BUFXCR_INVALID_MSTRID, base + QUADSPI_BUF0CR);
 	qspi_writel(q, QUADSPI_BUFXCR_INVALID_MSTRID, base + QUADSPI_BUF1CR);
 	qspi_writel(q, QUADSPI_BUFXCR_INVALID_MSTRID, base + QUADSPI_BUF2CR);
+
 	/*
-	 * Set ADATSZ with the maximum AHB buffer size to improve the
-	 * read performance.
+	 * Errata: A-009282: QuadSPI data prefetch may result in incorrect data
+	 * Workaround: Keep the read data size to 64 bits (8 bytes).
+	 * This disables the prefetch on the AHB buffer and
+	 * prevents this issue from occurring.
 	 */
-	qspi_writel(q, QUADSPI_BUF3CR_ALLMST_MASK |
-			((q->devtype_data->ahb_buf_size / 8)
-			<< QUADSPI_BUF3CR_ADATSZ_SHIFT),
-			base + QUADSPI_BUF3CR);
+	if (devtype_data->devtype == FSL_QUADSPI_LS2080A ||
+	    devtype_data->devtype == FSL_QUADSPI_LS1021A) {
+
+		qspi_writel(q, QUADSPI_BUF3CR_ALLMST_MASK |
+				(1 << QUADSPI_BUF3CR_ADATSZ_SHIFT),
+				base + QUADSPI_BUF3CR);
+
+	} else {
+		/*
+		 * Set ADATSZ with the maximum AHB buffer size to improve the
+		 * read performance.
+		*/
+		qspi_writel(q, QUADSPI_BUF3CR_ALLMST_MASK |
+				((q->devtype_data->ahb_buf_size / 8)
+				<< QUADSPI_BUF3CR_ADATSZ_SHIFT),
+				base + QUADSPI_BUF3CR);
+	}
 
 	/* We only use the buffer3 */
 	qspi_writel(q, 0, base + QUADSPI_BUF0IND);
-- 
2.1.0.27.g96db324