[PATCH 2/4] spi: pxa2xx: Translate ACPI DeviceSelection to Linux chip select on Baytrail

[Mika Westerberg <mika.westerberg@linux.intel.com>]

The Windows Baytrail SPI host controller driver uses 1 as the first (and
only) value for ACPI DeviceSelection like can be seen in DSDT taken from
Lenovo Thinkpad 10:

    Device (FPNT)
    {
        ...
        Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
        {
            Name (UBUF, ResourceTemplate ()
            {
                SpiSerialBus (0x0001, // DeviceSelection
                    PolarityLow, FourWireMode, 0x08,
                    ControllerInitiated, 0x007A1200, ClockPolarityLow,
                    ClockPhaseFirst, "\\_SB.SPI1",
                    0x00, ResourceConsumer,,)

This will fail to enumerate in Linux with following error:

[    0.241296] pxa2xx-spi 80860F0E:00: cs1 >= max 1
[    0.241312] spi_master spi32766: failed to add SPI device VFSI6101:00 from ACPI

To make the Linux SPI core successfully enumerate the device we provide a
custom version of ->fw_translate_cs() that translates DeviceSelection
correctly.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/spi/spi-pxa2xx.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index ab9914ad8365..baa98365a490 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -1328,11 +1328,30 @@ static int pxa2xx_spi_get_port_id(struct acpi_device *adev)
 		port_id = devid;
 	return port_id;
 }
+
+static int pxa2xx_spi_fw_translate_cs(struct spi_master *master, unsigned cs)
+{
+	struct driver_data *drv_data = spi_master_get_devdata(master);
+
+	switch (drv_data->ssp_type) {
+	/*
+	 * For Atoms the Windows driver starts enumerating chip selects
+	 * from 1 instead of 0 so translate it here to match what Linux
+	 * expects.
+	 */
+	case LPSS_BYT_SSP:
+		return cs - 1;
+
+	default:
+		return cs;
+	}
+}
 #else /* !CONFIG_ACPI */
 static int pxa2xx_spi_get_port_id(struct acpi_device *adev)
 {
 	return -1;
 }
+#define pxa2xx_spi_fw_translate_cs	NULL
 #endif
 
 /*
@@ -1490,6 +1509,7 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
 	master->setup = setup;
 	master->transfer_one_message = pxa2xx_spi_transfer_one_message;
 	master->unprepare_transfer_hardware = pxa2xx_spi_unprepare_transfer;
+	master->fw_translate_cs = pxa2xx_spi_fw_translate_cs;
 	master->auto_runtime_pm = true;
 
 	drv_data->ssp_type = ssp->type;
-- 
2.7.0.rc3