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

[Andrew Jeffery]

On Mon, 30 Mar 2020, at 12:24, Joel Stanley wrote:
> 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;

Reviewed-by: Andrew Jeffery <andrew at aj.id.au>