fsi/fsi-master-gpio: Sample input data on different clock phase

We currently sample the input data right after we toggle the
clock low, then high. The slave establishes the data on the
rising edge, so this is not ideal. We should sample it on
the low phase instead.

This currently works because we have an extra delay, but subsequent
patches will remove it.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Christopher Bostic <cbostic@linux.vnet.ibm.com>
Tested-by: Joel Stanley <joel@jms.id.au>

diff --git a/drivers/fsi/fsi-master-gpio.c b/drivers/fsi/fsi-master-gpio.c
index 4295a46780cb9a9d17f9abfda55b1bedc3db1190..d6508bbad1fb3168d94647dbf38d8d2a5c0748fe 100644 (file)
--- a/drivers/fsi/fsi-master-gpio.c
+++ b/drivers/fsi/fsi-master-gpio.c
@@ -86,12 +86,15 @@ static void clock_toggle(struct fsi_master_gpio *master, int count)
        }
 }
 
-static int sda_in(struct fsi_master_gpio *master)
+static int sda_clock_in(struct fsi_master_gpio *master)
 {
        int in;
 
        ndelay(FSI_GPIO_STD_DLY);
+       gpiod_set_value(master->gpio_clk, 0);
        in = gpiod_get_value(master->gpio_data);
+       ndelay(FSI_GPIO_STD_DLY);
+       gpiod_set_value(master->gpio_clk, 1);
        return in ? 1 : 0;
 }
 
@@ -126,8 +129,7 @@ static void serial_in(struct fsi_master_gpio *master, struct fsi_gpio_msg *msg,
        set_sda_input(master);
 
        for (bit = 0; bit < num_bits; bit++) {
-               clock_toggle(master, 1);
-               in_bit = sda_in(master);
+               in_bit = sda_clock_in(master);
                msg->msg <<= 1;
                msg->msg |= ~in_bit & 0x1;      /* Data is active low */
        }