linux-kernel - Re: [PATCH v3] spi: stm32-ospi: Make usage of reset_control

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Message-ID: <ee4e3e521434a0dadce058e7e5f3bbd77f598f90.camel@pengutronix.de>
Date: Thu, 08 May 2025 11:16:06 +0200
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Patrice Chotard <patrice.chotard@...s.st.com>, Mark Brown
 <broonie@...nel.org>, Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>
Cc: linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org, 
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3] spi: stm32-ospi: Make usage of
 reset_control_acquire/release() API

Hi Patrice,

On Mi, 2025-05-07 at 18:04 +0200, Patrice Chotard wrote:
> As ospi reset is consumed by both OMM and OSPI drivers, use the reset
> acquire/release mechanism which ensure exclusive reset usage.
> 
> This avoid to call reset_control_get/put() in OMM driver each time
> we need to reset OSPI children and guarantee the reset line stays
> deasserted.
> 
> Signed-off-by: Patrice Chotard <patrice.chotard@...s.st.com>
> ---
> Changes in v3:
>   - Remove previous patch 1/2 as already merged.
>   - Keep the reset control acquired from probe() to remove().
>   - Link to v2: https://lore.kernel.org/r/20250411-b4-upstream_ospi_reset_update-v2-0-4de7f5dd2a91@foss.st.com
> 
> Changes in v2:
>   - Rebased on spi/for-next (7a978d8fcf57).
>   - Remove useless check on reset.
>   - Add error handling on reset_control_acquire().
>   - Link to v1: https://lore.kernel.org/all/20250410-b4-upstream_ospi_reset_update-v1-0-74126a8ceb9c@foss.st.com/
> ---
>  drivers/spi/spi-stm32-ospi.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/spi/spi-stm32-ospi.c b/drivers/spi/spi-stm32-ospi.c
> index 668022098b1eac3628f0677e6d786e5a267346be..b2597b52beb1133155e0d6f601b0632ad4b8e8f5 100644
> --- a/drivers/spi/spi-stm32-ospi.c
> +++ b/drivers/spi/spi-stm32-ospi.c
> @@ -804,7 +804,7 @@ static int stm32_ospi_get_resources(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	ospi->rstc = devm_reset_control_array_get_optional_exclusive(dev);
> +	ospi->rstc = devm_reset_control_array_get_exclusive_released(dev);
>  	if (IS_ERR(ospi->rstc))
>  		return dev_err_probe(dev, PTR_ERR(ospi->rstc),
>  				     "Can't get reset\n");
> @@ -936,11 +936,13 @@ static int stm32_ospi_probe(struct platform_device *pdev)
>  	if (ret < 0)
>  		goto err_pm_enable;
>  
> -	if (ospi->rstc) {
> -		reset_control_assert(ospi->rstc);
> -		udelay(2);
> -		reset_control_deassert(ospi->rstc);
> -	}
> +	ret = reset_control_acquire(ospi->rstc);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Can not acquire reset %d\n", ret);
> +
> +	reset_control_assert(ospi->rstc);
> +	udelay(2);
> +	reset_control_deassert(ospi->rstc);
>  
>  	ret = spi_register_controller(ctrl);
>  	if (ret) {
> @@ -983,6 +985,8 @@ static void stm32_ospi_remove(struct platform_device *pdev)
>  	if (ospi->dma_chrx)
>  		dma_release_channel(ospi->dma_chrx);
>  
> +	reset_control_release(ospi->rstc);
> +
>  	pm_runtime_put_sync_suspend(ospi->dev);
>  	pm_runtime_force_suspend(ospi->dev);
>  }
> @@ -993,6 +997,8 @@ static int __maybe_unused stm32_ospi_suspend(struct device *dev)
>  
>  	pinctrl_pm_select_sleep_state(dev);
>  
> +	reset_control_release(ospi->rstc);

It would be nice to point out in a comment that OMM will temporarily
take over control during resume. But either way,

Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

regards
Philipp