linux-kernel - Re: [PATCH 1/2] spi: atmel-quadspi: Avoid overwriting delay register settings

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Message-ID: <20240926-macarena-wincing-7c4995487a29@thorsis.com>
Date: Thu, 26 Sep 2024 09:25:10 +0200
From: Alexander Dahl <ada@...rsis.com>
To: Mark Brown <broonie@...nel.org>
Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Tudor Ambarus <tudor.ambarus@...aro.org>,
	"open list:SPI SUBSYSTEM" <linux-spi@...r.kernel.org>,
	"moderated list:ARM/Microchip (AT91) SoC support" <linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] spi: atmel-quadspi: Avoid overwriting delay register
 settings

Hello everyone,

Am Wed, Sep 18, 2024 at 10:27:43AM +0200 schrieb Alexander Dahl:
> Previously the MR and SCR registers were just set with the supposedly
> required values, from cached register values (cached reg content
> initialized to zero).
> 
> All parts fixed here did not consider the current register (cache)
> content, which would make future support of cs_setup, cs_hold, and
> cs_inactive impossible.
> 
> Setting SCBR in atmel_qspi_setup() erases a possible DLYBS setting from
> atmel_qspi_set_cs_timing().  The DLYBS setting is applied by ORing over
> the current setting, without resetting the bits first.  All writes to MR
> did not consider possible settings of DLYCS and DLYBCT.
> 
> Signed-off-by: Alexander Dahl <ada@...rsis.com>
> Fixes: f732646d0ccd ("spi: atmel-quadspi: Add support for configuring CS timing")
> ---
>  drivers/spi/atmel-quadspi.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
> index 5aaff3bee1b7..fcd57cf1f2cf 100644
> --- a/drivers/spi/atmel-quadspi.c
> +++ b/drivers/spi/atmel-quadspi.c
> @@ -375,9 +375,9 @@ static int atmel_qspi_set_cfg(struct atmel_qspi *aq,
>  	 * If the QSPI controller is set in regular SPI mode, set it in
>  	 * Serial Memory Mode (SMM).
>  	 */
> -	if (aq->mr != QSPI_MR_SMM) {
> -		atmel_qspi_write(QSPI_MR_SMM, aq, QSPI_MR);
> -		aq->mr = QSPI_MR_SMM;
> +	if (!(aq->mr & QSPI_MR_SMM)) {
> +		aq->mr |= QSPI_MR_SMM;
> +		atmel_qspi_write(aq->scr, aq, QSPI_MR);

On a second glance, this looks wrong, value for Mode Register (MR) is
written into Serial Clock Register (SCR), should be like this instead:

    atmel_qspi_write(aq->mr, aq, QSPI_MR);

This is somewhat embarrassing, because the patch was already applied
to master.  Should it be reverted, then I would send a v2 of the
series?  Or should I send a quick fixup?

Greets
Alex

>  	}
>  
>  	/* Clear pending interrupts */
> @@ -501,7 +501,8 @@ static int atmel_qspi_setup(struct spi_device *spi)
>  	if (ret < 0)
>  		return ret;
>  
> -	aq->scr = QSPI_SCR_SCBR(scbr);
> +	aq->scr &= ~QSPI_SCR_SCBR_MASK;
> +	aq->scr |= QSPI_SCR_SCBR(scbr);
>  	atmel_qspi_write(aq->scr, aq, QSPI_SCR);
>  
>  	pm_runtime_mark_last_busy(ctrl->dev.parent);
> @@ -534,6 +535,7 @@ static int atmel_qspi_set_cs_timing(struct spi_device *spi)
>  	if (ret < 0)
>  		return ret;
>  
> +	aq->scr &= ~QSPI_SCR_DLYBS_MASK;
>  	aq->scr |= QSPI_SCR_DLYBS(cs_setup);
>  	atmel_qspi_write(aq->scr, aq, QSPI_SCR);
>  
> @@ -549,8 +551,8 @@ static void atmel_qspi_init(struct atmel_qspi *aq)
>  	atmel_qspi_write(QSPI_CR_SWRST, aq, QSPI_CR);
>  
>  	/* Set the QSPI controller by default in Serial Memory Mode */
> -	atmel_qspi_write(QSPI_MR_SMM, aq, QSPI_MR);
> -	aq->mr = QSPI_MR_SMM;
> +	aq->mr |= QSPI_MR_SMM;
> +	atmel_qspi_write(aq->mr, aq, QSPI_MR);
>  
>  	/* Enable the QSPI controller */
>  	atmel_qspi_write(QSPI_CR_QSPIEN, aq, QSPI_CR);
> -- 
> 2.39.5
> 
>