linux-kernel - Re: [PATCH v2 1/4] spi: bcm63xx-spi: add reset support

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Message-ID: <16650d01-7c5a-21be-35a8-c74ad0a47b45@gmail.com>
Date:   Mon, 15 Jun 2020 09:26:06 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Álvaro Fernández Rojas <noltari@...il.com>,
        broonie@...nel.org, f.fainelli@...il.com,
        bcm-kernel-feedback-list@...adcom.com, p.zabel@...gutronix.de,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/4] spi: bcm63xx-spi: add reset support



On 6/15/2020 2:09 AM, Álvaro Fernández Rojas wrote:
> bcm63xx arch resets the SPI controller at early boot. However, bmips arch
> needs to perform a reset when probing the driver.
> 
> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
> Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>
> ---
>  v2: use devm_reset_control_get_exclusive
> 
>  drivers/spi/spi-bcm63xx.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/spi/spi-bcm63xx.c b/drivers/spi/spi-bcm63xx.c
> index 0f1b10a4ef0c..8ab04affaf7b 100644
> --- a/drivers/spi/spi-bcm63xx.c
> +++ b/drivers/spi/spi-bcm63xx.c
> @@ -18,6 +18,7 @@
>  #include <linux/err.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/of.h>
> +#include <linux/reset.h>
>  
>  /* BCM 6338/6348 SPI core */
>  #define SPI_6348_RSET_SIZE		64
> @@ -493,6 +494,7 @@ static int bcm63xx_spi_probe(struct platform_device *pdev)
>  	struct bcm63xx_spi *bs;
>  	int ret;
>  	u32 num_cs = BCM63XX_SPI_MAX_CS;
> +	struct reset_control *reset;
>  
>  	if (dev->of_node) {
>  		const struct of_device_id *match;
> @@ -529,6 +531,15 @@ static int bcm63xx_spi_probe(struct platform_device *pdev)
>  		return PTR_ERR(clk);
>  	}
>  
> +	reset = devm_reset_control_get_exclusive(dev, NULL);
> +	if (IS_ERR(reset)) {
> +		ret = PTR_ERR(reset);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(dev,
> +				"failed to get reset controller: %d\n", ret);
> +		return ret;
> +	}

This should be devm_reset_control_get_exclusive_optional() for a number
of reasons the first one being the most important as it reflects reality
of the HW:

- not all BCM63xx platforms have a dedicated reset line for the SPI
controller (like the ARM-based SoCs)

- until you also update all Device Tree sources to have a 'resets'
property in their SPI controller node, this is likely going to be failing

This also applies to patch 3.
-- 
Florian