[PATCH linux dev-5.4 v2 2/2] fsi: aspeed: Support cabled FSI

[Joel Stanley]

On Mon, 30 Mar 2020 at 01:51, Joel Stanley <joel at jms.id.au> wrote:
>
> Some FSI development systems have internal FSI signals, and some have
> external cabled FSI. Software can detect which machine this is by
> reading a jumper GPIO, and also control which pins the signals are
> routed to through a mux GPIO.
>
> This attempts to find the GPIOs at probe time. If they are not present
> in the device tree the driver will not error and continue as before.
>
> The mux GPIO is owned by the FSI driver to ensure it is not modified at
> runtime. The routing jumper obtained as non-exclusive to allow other
> software to inspect it's state.
>
> Signed-off-by: Joel Stanley <joel at jms.id.au>
> ---
>  drivers/fsi/fsi-master-aspeed.c | 47 +++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
>
> diff --git a/drivers/fsi/fsi-master-aspeed.c b/drivers/fsi/fsi-master-aspeed.c
> index f49742b310c2..374e158ccdc7 100644
> --- a/drivers/fsi/fsi-master-aspeed.c
> +++ b/drivers/fsi/fsi-master-aspeed.c
> @@ -13,6 +13,7 @@
>  #include <linux/regmap.h>
>  #include <linux/slab.h>
>  #include <linux/iopoll.h>
> +#include <linux/gpio/consumer.h>
>
>  #include "fsi-master.h"
>
> @@ -419,6 +420,46 @@ static int aspeed_master_init(struct fsi_master_aspeed *aspeed)
>         return 0;
>  }
>
> +static int tacoma_cabled_fsi_fixup(struct device *dev)
> +{
> +       struct gpio_desc *routing_gpio, *mux_gpio;
> +       int gpio;
> +
> +       /*
> +        * The routing GPIO is a jumper indicating we should mux for the
> +        * externally connected FSI cable.
> +        */
> +       routing_gpio = devm_gpiod_get_optional(dev, "fsi-routing",
> +                       GPIOD_IN | GPIOD_FLAGS_BIT_NONEXCLUSIVE);
> +       if (IS_ERR(routing_gpio))
> +               return PTR_ERR(routing_gpio);
> +       if (!routing_gpio)
> +               return 0;
> +
> +       mux_gpio = devm_gpiod_get_optional(dev, "fsi-mux", GPIOD_ASIS);
> +       if (IS_ERR(mux_gpio))
> +               return PTR_ERR(mux_gpio);
> +       if (!mux_gpio)
> +               return 0;
> +
> +       gpio = gpiod_get_value(routing_gpio);
> +       if (gpio < 0)
> +               return 0;

Pretend this says:

       gpio = gpiod_get_value(routing_gpio);
       if (gpio < 0)
               return gpio;

> +
> +       /* If the routing GPIO is high we should set the mux to low. */
> +       if (gpio) {
> +               gpiod_direction_output(mux_gpio, 0);
> +               dev_info(dev, "FSI configured for external cable\n");
> +       } else {
> +               gpiod_direction_output(mux_gpio, 1);
> +       }
> +
> +       devm_gpiod_put(dev, routing_gpio);
> +
> +       return 0;
> +}
> +
> +
>  static int fsi_master_aspeed_probe(struct platform_device *pdev)
>  {
>         struct fsi_master_aspeed *aspeed;
> @@ -426,6 +467,12 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
>         int rc, links, reg;
>         __be32 raw;
>
> +       rc = tacoma_cabled_fsi_fixup(&pdev->dev);
> +       if (rc) {
> +               dev_err(&pdev->dev, "Tacoma FSI cable fixup failed\n");
> +               return rc;
> +       }
> +
>         aspeed = devm_kzalloc(&pdev->dev, sizeof(*aspeed), GFP_KERNEL);
>         if (!aspeed)
>                 return -ENOMEM;
> --
> 2.25.1
>