linux-kernel - Re: [PATCH v1 1/2] spi: spi-cadence: Add optional reset control support

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Date: Wed, 24 Apr 2024 18:54:10 -0700
From: Lars-Peter Clausen <lars@...afoo.de>
To: Ji Sheng Teoh <jisheng.teoh@...rfivetech.com>,
 Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
 Michal Simek <michal.simek@....com>
Cc: Ley Foon Tan <leyfoon.tan@...rfivetech.com>, linux-spi@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Eng Lee Teh <englee.teh@...rfivetech.com>
Subject: Re: [PATCH v1 1/2] spi: spi-cadence: Add optional reset control
 support

On 4/23/24 22:13, Ji Sheng Teoh wrote:
> Add optional reset control support for spi-cadence to properly bring
> the SPI device into an operating condition.
>
> Signed-off-by: Eng Lee Teh <englee.teh@...rfivetech.com>
> Signed-off-by: Ley Foon Tan <leyfoon.tan@...rfivetech.com>
> Signed-off-by: Ji Sheng Teoh <jisheng.teoh@...rfivetech.com>
> ---
>   drivers/spi/spi-cadence.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
>
> diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
> index e5140532071d..41f2f51d39e4 100644
> --- a/drivers/spi/spi-cadence.c
> +++ b/drivers/spi/spi-cadence.c
> @@ -111,6 +111,7 @@
>    * @dev_busy:		Device busy flag
>    * @is_decoded_cs:	Flag for decoder property set or not
>    * @tx_fifo_depth:	Depth of the TX FIFO
> + * @rstc:		Optional reset control for SPI controller
>    */
>   struct cdns_spi {
>   	void __iomem *regs;
> @@ -125,6 +126,7 @@ struct cdns_spi {
>   	u8 dev_busy;
>   	u32 is_decoded_cs;
>   	unsigned int tx_fifo_depth;
> +	struct reset_control *rstc;
>   };
>   
>   /* Macros for the SPI controller read/write */
> @@ -588,6 +590,16 @@ static int cdns_spi_probe(struct platform_device *pdev)
>   		goto remove_ctlr;
>   	}
>   
> +	xspi->rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);

The cadence SPI core has 3 different resets signals. Maybe use a name 
for the reset to make it clear which reset this is referring to.

> +	if (IS_ERR(xspi->rstc)) {
> +		ret = PTR_ERR(xspi->rstc);
> +		dev_err(&pdev->dev, "Cannot get SPI reset.\n");
> +		goto remove_ctlr;
> +	}
> +
> +	reset_control_assert(xspi->rstc);
> +	reset_control_deassert(xspi->rstc);
> +
>   	if (!spi_controller_is_target(ctlr)) {
>   		xspi->ref_clk = devm_clk_get_enabled(&pdev->dev, "ref_clk");
>   		if (IS_ERR(xspi->ref_clk)) {