spi: pxa2xx: Add output control for multiple Intel LPSS chip selects

Intel LPSS SPI host controllers in upcoming Intel platforms can have up
to 4 chip selects per port. Extend chip select control in
lpss_ssp_cs_control() by adding a code that selects the active chip
select output prior to changing the state. Detection for number of
enabled chip select signals will be added by another patch.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 24 insertions, 3 deletions

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index 9060aee5a7b1..040f6bb566a1 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -64,6 +64,8 @@ MODULE_ALIAS("platform:pxa2xx-spi");
 #define LPSS_GENERAL_REG_RXTO_HOLDOFF_DISABLE   BIT(24)
 #define LPSS_CS_CONTROL_SW_MODE                 BIT(0)
 #define LPSS_CS_CONTROL_CS_HIGH                 BIT(1)
+#define LPSS_CS_CONTROL_CS_SEL_SHIFT            8
+#define LPSS_CS_CONTROL_CS_SEL_MASK             (3 << LPSS_CS_CONTROL_CS_SEL_SHIFT)
 
 struct lpss_config {
         /* LPSS offset from drv_data->ioaddr */
@@ -271,15 +273,34 @@ static void lpss_ssp_setup(struct driver_data *drv_data)
 static void lpss_ssp_cs_control(struct driver_data *drv_data, bool enable)
 {
         const struct lpss_config *config;
-        u32 value;
+        u32 value, cs;
 
         config = lpss_get_config(drv_data);
 
         value = __lpss_ssp_read_priv(drv_data, config->reg_cs_ctrl);
-        if (enable)
+        if (enable) {
+                cs = drv_data->cur_msg->spi->chip_select;
+                cs <<= LPSS_CS_CONTROL_CS_SEL_SHIFT;
+                if (cs != (value & LPSS_CS_CONTROL_CS_SEL_MASK)) {
+                        /*
+                         * When switching another chip select output active
+                         * the output must be selected first and wait 2 ssp_clk
+                         * cycles before changing state to active. Otherwise
+                         * a short glitch will occur on the previous chip
+                         * select since output select is latched but state
+                         * control is not.
+                         */
+                        value &= ~LPSS_CS_CONTROL_CS_SEL_MASK;
+                        value |= cs;
+                        __lpss_ssp_write_priv(drv_data,
+                                              config->reg_cs_ctrl, value);
+                        ndelay(1000000000 /
+                               (drv_data->master->max_speed_hz / 2));
+                }
                 value &= ~LPSS_CS_CONTROL_CS_HIGH;
-        else
+        } else {
                 value |= LPSS_CS_CONTROL_CS_HIGH;
+        }
         __lpss_ssp_write_priv(drv_data, config->reg_cs_ctrl, value);
 }