On Fri, Jul 27, 2018 at 10:53 PM, Alexandre Belloni
<alexandre.belloni@xxxxxxxxxxx> wrote:
> Because the SPI controller deasserts the chip select when the TX fifo is
> empty (which may happen in the middle of a transfer), the CS should be
> handled by linux. Unfortunately, some or all of the first four chip
> selects are not muxable as GPIOs, depending on the SoC.
>
> There is a way to bitbang those pins by using the SPI boot controller so
> use it to set the chip selects.
>
> At init time, it is also necessary to give control of the SPI interface to
> the Designware IP.
>
FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
> ---
> Changes in v3:
> - use dw_spi_set_cs instead of open coding
> - few small improvements suggested by Andy
> - changed the comment to be clearer regarding which IP is used on the SoC
> - removed useless dt bindings change
>
> Change in v2:
> - correctly use device_get_match_data to retrieve the init function instead of
> hardcoding it.
>
> drivers/spi/spi-dw-mmio.c | 90 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 90 insertions(+)
>
> diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
> index d25cc4037e23..e80f60ed6fdf 100644
> --- a/drivers/spi/spi-dw-mmio.c
> +++ b/drivers/spi/spi-dw-mmio.c
> @@ -15,11 +15,13 @@
> #include <linux/slab.h>
> #include <linux/spi/spi.h>
> #include <linux/scatterlist.h>
> +#include <linux/mfd/syscon.h>
> #include <linux/module.h>
> #include <linux/of.h>
> #include <linux/of_gpio.h>
> #include <linux/of_platform.h>
> #include <linux/property.h>
> +#include <linux/regmap.h>
>
> #include "spi-dw.h"
>
> @@ -28,10 +30,90 @@
> struct dw_spi_mmio {
> struct dw_spi dws;
> struct clk *clk;
> + void *priv;
> };
>
> +#define MSCC_CPU_SYSTEM_CTRL_GENERAL_CTRL 0x24
> +#define OCELOT_IF_SI_OWNER_MASK GENMASK(5, 4)
> +#define OCELOT_IF_SI_OWNER_OFFSET 4
> +#define MSCC_IF_SI_OWNER_SISL 0
> +#define MSCC_IF_SI_OWNER_SIBM 1
> +#define MSCC_IF_SI_OWNER_SIMC 2
> +
> +#define MSCC_SPI_MST_SW_MODE 0x14
> +#define MSCC_SPI_MST_SW_MODE_SW_PIN_CTRL_MODE BIT(13)
> +#define MSCC_SPI_MST_SW_MODE_SW_SPI_CS(x) (x << 5)
> +
> +struct dw_spi_mscc {
> + struct regmap *syscon;
> + void __iomem *spi_mst;
> +};
> +
> +/*
> + * 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
> + * the SPI boot controller registers. the final chip select is an OR gate
> + * between the Designware SPI controller and the SPI boot controller.
> + */
> +static void dw_spi_mscc_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 dw_spi_mscc *dwsmscc = dwsmmio->priv;
> + u32 cs = spi->chip_select;
> +
> + if (cs < 4) {
> + u32 sw_mode = MSCC_SPI_MST_SW_MODE_SW_PIN_CTRL_MODE;
> +
> + if (!enable)
> + sw_mode |= MSCC_SPI_MST_SW_MODE_SW_SPI_CS(BIT(cs));
> +
> + writel(sw_mode, dwsmscc->spi_mst + MSCC_SPI_MST_SW_MODE);
> + }
> +
> + dw_spi_set_cs(spi, enable);
> +}
> +
> +static int dw_spi_mscc_init(struct platform_device *pdev,
> + struct dw_spi_mmio *dwsmmio)
> +{
> + struct dw_spi_mscc *dwsmscc;
> + struct resource *res;
> +
> + dwsmscc = devm_kzalloc(&pdev->dev, sizeof(*dwsmscc), GFP_KERNEL);
> + if (!dwsmscc)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> + dwsmscc->spi_mst = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(dwsmscc->spi_mst)) {
> + dev_err(&pdev->dev, "SPI_MST region map failed\n");
> + return PTR_ERR(dwsmscc->spi_mst);
> + }
> +
> + dwsmscc->syscon = syscon_regmap_lookup_by_compatible("mscc,ocelot-cpu-syscon");
> + if (IS_ERR(dwsmscc->syscon))
> + return PTR_ERR(dwsmscc->syscon);
> +
> + /* Deassert all CS */
> + writel(0, dwsmscc->spi_mst + MSCC_SPI_MST_SW_MODE);
> +
> + /* Select the owner of the SI interface */
> + regmap_update_bits(dwsmscc->syscon, MSCC_CPU_SYSTEM_CTRL_GENERAL_CTRL,
> + OCELOT_IF_SI_OWNER_MASK,
> + MSCC_IF_SI_OWNER_SIMC << OCELOT_IF_SI_OWNER_OFFSET);
> +
> + dwsmmio->dws.set_cs = dw_spi_mscc_set_cs;
> + dwsmmio->priv = dwsmscc;
> +
> + return 0;
> +}
> +
> static int dw_spi_mmio_probe(struct platform_device *pdev)
> {
> + int (*init_func)(struct platform_device *pdev,
> + struct dw_spi_mmio *dwsmmio);
> struct dw_spi_mmio *dwsmmio;
> struct dw_spi *dws;
> struct resource *mem;
> @@ -99,6 +181,13 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
> }
> }
>
> + init_func = device_get_match_data(&pdev->dev);
> + if (init_func) {
> + ret = init_func(pdev, dwsmmio);
> + if (ret)
> + goto out;
> + }
> +
> ret = dw_spi_add_host(&pdev->dev, dws);
> if (ret)
> goto out;
> @@ -123,6 +212,7 @@ static int dw_spi_mmio_remove(struct platform_device *pdev)
>
> static const struct of_device_id dw_spi_mmio_of_match[] = {
> { .compatible = "snps,dw-apb-ssi", },
> + { .compatible = "mscc,ocelot-spi", .data = dw_spi_mscc_init},
> { /* end of table */}
> };
> MODULE_DEVICE_TABLE(of, dw_spi_mmio_of_match);
> --
> 2.18.0
>
--
With Best Regards,
Andy Shevchenko
