linux-kernel - Re: [PATCH] mtd: spi-nor: cadence-quadspi: add reset control

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Date:   Tue, 9 Apr 2019 16:20:48 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Dinh Nguyen <dinguyen@...nel.org>, <linux-mtd@...ts.infradead.org>
CC:     <marex@...x.de>, Tien-Fong Chee <tien.fong.chee@...el.com>,
        <bbrezillon@...nel.org>, <tudor.ambarus@...rochip.com>,
        <linux-kernel@...r.kernel.org>, <computersforpeace@...il.com>,
        <dwmw2@...radead.org>
Subject: Re: [PATCH] mtd: spi-nor: cadence-quadspi: add reset control



On 08/04/19 10:20 PM, Dinh Nguyen wrote:
> Get the reset control for the QSPI controller and bring it out of reset.
> 
> Suggested-by: Tien-Fong Chee <tien.fong.chee@...el.com>
> Signed-off-by: Dinh Nguyen <dinguyen@...nel.org>
> ---
>  drivers/mtd/spi-nor/cadence-quadspi.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> index 792628750eec..710a853f9d13 100644
> --- a/drivers/mtd/spi-nor/cadence-quadspi.c
> +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
> @@ -34,6 +34,7 @@
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/reset.h>
>  #include <linux/sched.h>
>  #include <linux/spi/spi.h>
>  #include <linux/timer.h>
> @@ -1336,6 +1337,7 @@ static int cqspi_probe(struct platform_device *pdev)
>  	struct cqspi_st *cqspi;
>  	struct resource *res;
>  	struct resource *res_ahb;
> +	struct reset_control *rstc;
>  	const struct cqspi_driver_platdata *ddata;
>  	int ret;
>  	int irq;
> @@ -1362,6 +1364,14 @@ static int cqspi_probe(struct platform_device *pdev)
>  		return PTR_ERR(cqspi->clk);
>  	}
>  
> +	/* Obtain QSPI reset control */
> +	rstc = devm_reset_control_get_exclusive(dev, NULL);
> +	if (!IS_ERR(rstc)) {
> +		reset_control_assert(rstc);
> +		udelay(1);
> +		reset_control_deassert(rstc);
> +	}
> +

If reset is optional here why not use
devm_reset_control_get_optional_exclusive() and handle error codes (like
-EPROBE_DEFER) appropriately instead of ignoring them?

>  	/* Obtain and remap controller address. */
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	cqspi->iobase = devm_ioremap_resource(dev, res);
> 

-- 
Regards
Vignesh