Re: [PATCH v10 10/15] spi: dw: Add support for AMD Pensando Elba SoC

[Serge Semin <fancer.lancer@xxxxxxxxx>]

On Sun, Mar 05, 2023 at 08:07:34PM -0800, Brad Larson wrote:
> The AMD Pensando Elba SoC includes a DW apb_ssi v4 controller
> with device specific chip-select control.  The Elba SoC
> provides four chip-selects where the native DW IP supports
> two chip-selects.  The Elba DW_SPI instance has two native
> CS signals that are always overridden.
> 
> Signed-off-by: Brad Larson <blarson@xxxxxxx>
> ---
> 
> v10 changes:
> - Delete struct dw_spi_elba, use regmap directly in priv
> 
> v9 changes:
> - Add use of macros GENMASK() and BIT()
> - Change ELBA_SPICS_SHIFT() to ELBA_SPICS_OFFSET()
> 
> ---
>  drivers/spi/spi-dw-mmio.c | 65 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
> index 26c40ea6dd12..2076cb83a11b 100644
> --- a/drivers/spi/spi-dw-mmio.c
> +++ b/drivers/spi/spi-dw-mmio.c
> @@ -53,6 +53,20 @@ struct dw_spi_mscc {
>  	void __iomem        *spi_mst; /* Not sparx5 */
>  };
>  
> +/*
> + * Elba SoC does not use ssi, pin override is used for cs 0,1 and
> + * gpios for cs 2,3 as defined in the device tree.
> + *
> + * cs:  |       1               0
> + * bit: |---3-------2-------1-------0
> + *      |  cs1   cs1_ovr   cs0   cs0_ovr
> + */
> +#define ELBA_SPICS_REG			0x2468
> +#define ELBA_SPICS_OFFSET(cs)		((cs) << 1)
> +#define ELBA_SPICS_MASK(cs)		(GENMASK(1, 0) << ELBA_SPICS_OFFSET(cs))
> +#define ELBA_SPICS_SET(cs, val)		\
> +		((((val) << 1) | BIT(0)) << ELBA_SPICS_OFFSET(cs))
> +
>  /*
>   * The Designware SPI controller (referred to as master in the documentation)
>   * automatically deasserts chip select when the tx fifo is empty. The chip
> @@ -237,6 +251,56 @@ static int dw_spi_canaan_k210_init(struct platform_device *pdev,
>  	return 0;
>  }
>  
> +static void dw_spi_elba_override_cs(struct regmap *syscon, int cs, int enable)
> +{
> +	regmap_update_bits(syscon, ELBA_SPICS_REG, ELBA_SPICS_MASK(cs),
> +			   ELBA_SPICS_SET(cs, enable));
> +}
> +
> +static void dw_spi_elba_set_cs(struct spi_device *spi, bool enable)
> +{
> +	struct dw_spi *dws = spi_master_get_devdata(spi->master);
> +	struct dw_spi_mmio *dwsmmio = container_of(dws, struct dw_spi_mmio, dws);
> +	struct regmap *syscon = dwsmmio->priv;
> +	u8 cs;
> +
> +	cs = spi->chip_select;
> +	if (cs < 2)
> +		dw_spi_elba_override_cs(syscon, spi->chip_select, enable);
> +
> +	/*
> +	 * The DW SPI controller needs a native CS bit selected to start
> +	 * the serial engine.
> +	 */
> +	spi->chip_select = 0;
> +	dw_spi_set_cs(spi, enable);
> +	spi->chip_select = cs;
> +}
> +
> +static int dw_spi_elba_init(struct platform_device *pdev,
> +			    struct dw_spi_mmio *dwsmmio)
> +{
> +	const char *syscon_name = "amd,pensando-elba-syscon";

> +	struct device_node *np = pdev->dev.of_node;

Drop this since it's used only once below. 
                                                                          
> +	struct device_node *node;                                         
> +	struct regmap *syscon;                                            
> +                                                                       
> -	node = of_parse_phandle(np, syscon_name, 0);                      

	node = of_parse_phandle(dev_of_node(pdev->dev), syscon_name, 0);

> +	if (!node)

> +		return dev_err_probe(&pdev->dev, -ENODEV, "failed to find %s\n",
> +				     syscon_name);

Hm, using dev_err_probe() with known error value seems overkill.

> +

> +	syscon = syscon_node_to_regmap(node);
> +	if (IS_ERR(syscon))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(syscon),
> +				     "syscon regmap lookup failed\n");

of_node_put() is missing in the error and success paths.

-Serge(y)

> +
> +	dwsmmio->priv = syscon;
> +	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,
> @@ -352,6 +416,7 @@ static const struct of_device_id dw_spi_mmio_of_match[] = {
>  	{ .compatible = "intel,thunderbay-ssi", .data = dw_spi_intel_init},
>  	{ .compatible = "microchip,sparx5-spi", dw_spi_mscc_sparx5_init},
>  	{ .compatible = "canaan,k210-spi", dw_spi_canaan_k210_init},
> +	{ .compatible = "amd,pensando-elba-spi", .data = dw_spi_elba_init},
>  	{ /* end of table */}
>  };
>  MODULE_DEVICE_TABLE(of, dw_spi_mmio_of_match);
> -- 
> 2.17.1
>