Re: [PATCH v2 3/5] spi: stm32: move splitting transfers to optimize_message

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 19 Feb 2024 16:33:20 -0600
David Lechner <dlechner@baylibre.com> wrote:

> Since splitting transfers was moved to spi_optimize_message() in the
> core SPI code, we now need to use the optimize_message callback in the
> STM32 SPI driver to ensure that the operation is only performed once
> when spi_optimize_message() is used by peripheral drivers explicitly.
> 
> Signed-off-by: David Lechner <dlechner@baylibre.com>
Trivial comment inline. Otherwise LGTM
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

There are changes to when this happens wrt to locking but I think those
are all positive as the bus lock is held for less time and there
is nothing in here that needs that lock held.
> ---
> 
> v2 changes: none
> 
>  drivers/spi/spi-stm32.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
> index c32e57bb38bd..e4e7ddb7524a 100644
> --- a/drivers/spi/spi-stm32.c
> +++ b/drivers/spi/spi-stm32.c
> @@ -1118,6 +1118,21 @@ static irqreturn_t stm32h7_spi_irq_thread(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>  
> +static int stm32_spi_optimize_message(struct spi_message *msg)
> +{
> +	struct spi_controller *ctrl = msg->spi->controller;
> +	struct stm32_spi *spi = spi_controller_get_devdata(ctrl);
> +
> +	/* On STM32H7, messages should not exceed a maximum size set
If you spin a v3, this isn't in keeping with local comment style.

	/*
 	 * On...

> +	 * later via the set_number_of_data function. In order to
> +	 * ensure that, split large messages into several messages
> +	 */
> +	if (spi->cfg->set_number_of_data)
> +		return spi_split_transfers_maxwords(ctrl, msg, spi->t_size_max);
> +
> +	return 0;
> +}
> +
>  /**
>   * stm32_spi_prepare_msg - set up the controller to transfer a single message
>   * @ctrl: controller interface
> @@ -1163,18 +1178,6 @@ static int stm32_spi_prepare_msg(struct spi_controller *ctrl,
>  		!!(spi_dev->mode & SPI_LSB_FIRST),
>  		!!(spi_dev->mode & SPI_CS_HIGH));
>  
> -	/* On STM32H7, messages should not exceed a maximum size setted
> -	 * afterward via the set_number_of_data function. In order to
> -	 * ensure that, split large messages into several messages
> -	 */
> -	if (spi->cfg->set_number_of_data) {
> -		int ret;
> -
> -		ret = spi_split_transfers_maxwords(ctrl, msg, spi->t_size_max);
> -		if (ret)
> -			return ret;
> -	}
> -
>  	spin_lock_irqsave(&spi->lock, flags);
>  
>  	/* CPOL, CPHA and LSB FIRST bits have common register */
> @@ -2180,6 +2183,7 @@ static int stm32_spi_probe(struct platform_device *pdev)
>  	ctrl->max_speed_hz = spi->clk_rate / spi->cfg->baud_rate_div_min;
>  	ctrl->min_speed_hz = spi->clk_rate / spi->cfg->baud_rate_div_max;
>  	ctrl->use_gpio_descriptors = true;
> +	ctrl->optimize_message = stm32_spi_optimize_message;
>  	ctrl->prepare_message = stm32_spi_prepare_msg;
>  	ctrl->transfer_one = stm32_spi_transfer_one;
>  	ctrl->unprepare_message = stm32_spi_unprepare_msg;
>