linux-kernel - Re: [PATCH v2 03/13] spi: dw: Add support for Pensando Elba SoC SPI

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Date:   Wed, 31 Mar 2021 21:00:18 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Brad Larson <brad@...sando.io>
Cc:     linux-arm-kernel@...ts.infradead.org, arnd@...db.de,
        linus.walleij@...aro.org, bgolaszewski@...libre.com,
        broonie@...nel.org, adrian.hunter@...el.com,
        ulf.hansson@...aro.org, olof@...om.net, linux-gpio@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/13] spi: dw: Add support for Pensando Elba SoC SPI

On Sun, Mar 28, 2021 at 06:59:28PM -0700, Brad Larson wrote:
> The Pensando Elba SoC uses a GPIO based chip select
> for two DW SPI busses with each bus having two
> chip selects.
> 
> Signed-off-by: Brad Larson <brad@...sando.io>
> ---
>  drivers/spi/spi-dw-mmio.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
> index 17c06039a74d..c323a5ceecb8 100644
> --- a/drivers/spi/spi-dw-mmio.c
> +++ b/drivers/spi/spi-dw-mmio.c
> @@ -56,7 +56,7 @@ struct dw_spi_mscc {
>  /*
>   * The Designware SPI controller (referred to as master in the documentation)
>   * automatically deasserts chip select when the tx fifo is empty. The chip
> - * selects then needs to be either driven as GPIOs or, for the first 4 using the
> + * selects then needs to be either driven as GPIOs or, for the first 4 using
>   * the SPI boot controller registers. the final chip select is an OR gate
>   * between the Designware SPI controller and the SPI boot controller.
>   */
> @@ -237,6 +237,31 @@ static int dw_spi_canaan_k210_init(struct platform_device *pdev,
>  	return 0;
>  }
>  
> +static void dw_spi_elba_set_cs(struct spi_device *spi, bool enable)
> +{
> +	struct dw_spi *dws = spi_master_get_devdata(spi->master);
> +

> +	if (!enable) {

Please, be more attentive to the review-comments given to you before
resending a new patchset. One more time. This version of set_cs won't
work for Active-high CS. Each SPI controller working with GPIO-based
chip-select is marked as supporting that feature. So your DW
SPI controller won't be able to work correctly with SPI-devices
activated by active-high chip-select signal. Note default
dw_spi_set_cs() callback supports that.

-Sergey

> +		/*
> +		 * Using a GPIO-based chip-select, the DW SPI
> +		 * controller still needs its own CS bit selected
> +		 * to start the serial engine.  On Elba the specific
> +		 * CS doesn't matter to start the serial engine,
> +		 * so using CS0.
> +		 */
> +		dw_writel(dws, DW_SPI_SER, BIT(0));
> +	} else {
> +		dw_writel(dws, DW_SPI_SER, 0);
> +	}
> +}
> +
> +static int dw_spi_elba_init(struct platform_device *pdev,
> +			    struct dw_spi_mmio *dwsmmio)
> +{
> +	dwsmmio->dws.set_cs = dw_spi_elba_set_cs;
> +	return 0;
> +}
> +
>  static int dw_spi_mmio_probe(struct platform_device *pdev)
>  {
>  	int (*init_func)(struct platform_device *pdev,
> @@ -351,6 +376,7 @@ static const struct of_device_id dw_spi_mmio_of_match[] = {
>  	{ .compatible = "intel,keembay-ssi", .data = dw_spi_keembay_init},
>  	{ .compatible = "microchip,sparx5-spi", dw_spi_mscc_sparx5_init},
>  	{ .compatible = "canaan,k210-spi", dw_spi_canaan_k210_init},
> +	{ .compatible = "pensando,elba-spi", .data = dw_spi_elba_init},
>  	{ /* end of table */}
>  };
>  MODULE_DEVICE_TABLE(of, dw_spi_mmio_of_match);
> -- 
> 2.17.1
>