linux-kernel - [PATCH v2 01/10] spi: atmel-quadspi: cache MR value to avoid a write access

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Date:   Thu, 31 Jan 2019 16:15:28 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <broonie@...nel.org>, <robh+dt@...nel.org>, <mark.rutland@....com>,
        <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <Ludovic.Desroches@...rochip.com>, <bbrezillon@...nel.org>
CC:     <linux-spi@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        <Tudor.Ambarus@...rochip.com>
Subject: [PATCH v2 01/10] spi: atmel-quadspi: cache MR value to avoid a write
 access

From: Tudor Ambarus <tudor.ambarus@...rochip.com>

Cache MR value to avoid write access when setting the controller
in Serial Memory Mode (SMM). SMM is set in exec_op() and not at
probe time, to let room for future regular SPI support.

Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
---
v2: cache MR value instead of moving the write access at probe

 drivers/spi/atmel-quadspi.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
index ddc712410812..fe05aee5d845 100644
--- a/drivers/spi/atmel-quadspi.c
+++ b/drivers/spi/atmel-quadspi.c
@@ -155,6 +155,7 @@ struct atmel_qspi {
 	struct clk		*clk;
 	struct platform_device	*pdev;
 	u32			pending;
+	u32			mr;
 	struct completion	cmd_completion;
 };
 
@@ -238,7 +239,9 @@ static int atmel_qspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
 	icr = QSPI_ICR_INST(op->cmd.opcode);
 	ifr = QSPI_IFR_INSTEN;
 
-	qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);
+	/* Set the QSPI controller in Serial Memory Mode */
+	if (!(aq->mr & QSPI_MR_SMM))
+		qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);
 
 	mode = find_mode(op);
 	if (mode < 0)
-- 
2.9.5