linux-kernel - Re: [PATCH v4 01/13] spi: atmel-quadspi: cache MR value to avoid a write access

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Message-ID: <20190204150005.3567bf29@bbrezillon>
Date:   Mon, 4 Feb 2019 15:00:05 +0100
From:   Boris Brezillon <bbrezillon@...nel.org>
To:     <Tudor.Ambarus@...rochip.com>
Cc:     <broonie@...nel.org>, <robh+dt@...nel.org>, <mark.rutland@....com>,
        <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <Ludovic.Desroches@...rochip.com>, <Cyrille.Pitchen@...rochip.com>,
        <bugalski.piotr@...il.com>, <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>
Subject: Re: [PATCH v4 01/13] spi: atmel-quadspi: cache MR value to avoid a
 write access

On Mon, 4 Feb 2019 10:09:22 +0000
<Tudor.Ambarus@...rochip.com> wrote:

> From: Tudor Ambarus <tudor.ambarus@...rochip.com>
> 
> Set the controller by default in Serial Memory Mode (SMM) at probe.
> Cache Mode Register (MR) value to avoid write access when setting
> the controller in serial memory mode at exec_op().
> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>

Reviewed-by: Boris Brezillon <bbrezillon@...nel.org>

> ---
> v4: s/smm/mr, init controller in serial memory mode by default
> v3: update smm value when different. rename mr/smm
> v2: cache MR value instead of moving the write access at probe
> 
>  drivers/spi/atmel-quadspi.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
> index ddc712410812..d6864d29f294 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 +239,14 @@ 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);
> +	/*
> +	 * If the QSPI controller is set in regular SPI mode, set it in
> +	 * Serial Memory Mode (SMM).
> +	 */
> +	if (aq->mr != QSPI_MR_SMM) {
> +		qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);
> +		aq->mr = QSPI_MR_SMM;
> +	}
>  
>  	mode = find_mode(op);
>  	if (mode < 0)
> @@ -381,6 +389,10 @@ static int atmel_qspi_init(struct atmel_qspi *aq)
>  	/* Reset the QSPI controller */
>  	qspi_writel(aq, QSPI_CR, QSPI_CR_SWRST);
>  
> +	/* Set the QSPI controller by default in Serial Memory Mode */
> +	qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);
> +	aq->mr = QSPI_MR_SMM;
> +
>  	/* Enable the QSPI controller */
>  	qspi_writel(aq, QSPI_CR, QSPI_CR_QSPIEN);
>