spi: dw: Bail out early on unsupported target mode

Currently, the DesignWare SPI controller driver supports only host mode.
However, spi2 on the Kendryte K210 SoC supports only target mode,
triggering an error message on e.g. SiPEED MAiXBiT since commit
98d75b9ef282f6b9 ("spi: dw: Drop default number of CS setting"):

    dw_spi_mmio 50240000.spi: error -22: problem registering spi host
    dw_spi_mmio 50240000.spi: probe with driver dw_spi_mmio failed with error -22

As spi2 rightfully has no "num-cs" property, num_chipselect is now zero,
causing spi_alloc_host() to fail to register the controller.  Before,
the driver silently registered an SPI host controller with 4 chip
selects.

Reject target mode early on and warn the user, getting rid of the
error message.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/7ae28d83bff7351f34782658ae1bb69cc731693e.1715163113.git.geert+renesas@glider.be
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index c56de35eca988ee46e9a10de650fc2159cc603cc..819907e332c4b004f162067c0892a2db4a2171b7 100644 (file)
--- a/drivers/spi/spi-dw-mmio.c
+++ b/drivers/spi/spi-dw-mmio.c
@@ -321,6 +321,11 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
        struct dw_spi *dws;
        int ret;
 
+       if (device_property_read_bool(&pdev->dev, "spi-slave")) {
+               dev_warn(&pdev->dev, "spi-slave is not yet supported\n");
+               return -ENODEV;
+       }
+
        dwsmmio = devm_kzalloc(&pdev->dev, sizeof(struct dw_spi_mmio),
                        GFP_KERNEL);
        if (!dwsmmio)