linux-kernel - Re: [PATCHv2] mtd: spi-nor: cadence-quadspi: add reset control

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Message-ID: <5e058af4-17d8-9db9-5bc5-2122d3af4c9f@microchip.com>
Date:   Wed, 17 Apr 2019 08:48:45 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <dinguyen@...nel.org>, <linux-mtd@...ts.infradead.org>
CC:     <marex@...x.de>, <dwmw2@...radead.org>,
        <computersforpeace@...il.com>, <bbrezillon@...nel.org>,
        <vigneshr@...com>, <linux-kernel@...r.kernel.org>,
        <tien.fong.chee@...el.com>
Subject: Re: [PATCHv2] mtd: spi-nor: cadence-quadspi: add reset control

Hi, Dinh,

On 04/09/2019 06:38 PM, Dinh Nguyen wrote:
> Get the reset control for the QSPI controller and bring it out of reset.

Is there a public datasheet where I can check this?
> 
> Suggested-by: Tien-Fong Chee <tien.fong.chee@...el.com>
> Signed-off-by: Dinh Nguyen <dinguyen@...nel.org>
> ---
> v2: use devm_reset_control_get_optional_exclusive
>     print an error message
>     return -EPROBE_DEFER
> ---
>  drivers/mtd/spi-nor/cadence-quadspi.c | 14 ++++++++++++++

would you update the bindings as well?

>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> index 792628750eec..c548567adcf0 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 +1364,18 @@ static int cqspi_probe(struct platform_device *pdev)
>  		return PTR_ERR(cqspi->clk);
>  	}
>  
> +	/* Obtain QSPI reset control */

OSPI version of the IP has been added recently. Is this available just for QSPI?

> +	rstc = devm_reset_control_get_optional_exclusive(dev, NULL);
> +	if (IS_ERR(rstc)) {
> +		dev_err(dev, "Cannot get QSPI reset.\n");
> +		if (PTR_ERR(rstc) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;

why ignoring all the other possible errors? Maybe return PTR_ERR(rstc); ?

> +	} else {
> +		reset_control_assert(rstc);

Shouldn't the clock be enabled before asserting reset?

Does it matter if reset_control_assert() is returning any error?

> +		udelay(1);

Is there a range or 1 us is the maximum time that we should wait?

> +		reset_control_deassert(rstc);

Should we check if reset_control_deassert() is returning any error?

Cheers,
ta

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