[U-Boot] [PATCH v3 4/8] reset: socfpga: add reset handling for old kernels

[Simon Goldschmidt]

On Fri, Mar 1, 2019 at 1:00 PM Marek Vasut <marex at denx.de> wrote:
>
> On 2/26/19 9:31 PM, Simon Goldschmidt wrote:
> > This adds code to take peripherals out of reset based on an environment
> > variable. This is in preparation for removing the code that does this from
> > SPL.
> >
> > However, some drivers even in current Linux cannot handle peripheral reset,
> > so until this works, we need a compatibility workaround.
> >
> > This workaround is implemented in the 'assert' and 'remove' callbacks of
> > this reset driver: the 'assert' callback does not disable peripherals that
> > were already taken out of reset, while the 'remove' callback, which is
> > called on OS_PREPARE, deasserts all peripheral resets if the environment
> > variable "socfpga_legacy_reset_compat" is set to 1, which is what the gen5
> > SPL did up to now.
> >
> > This is in preparation to clean up the SPL and implementing proper reset
> > handling for U-Boot.
> >
> > Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
> > ---
> >
> > Changes in v3:
> > - fix falcon mode in SPL should work, too
> > - change env var name "socfpga_permodrst_ungate" to
> >   "socfpga_legacy_reset_compat"
> > - in compat mode, don't reset peripherals once they are enabled
> >
> > Changes in v2:
> > - moved from Kernel option "OLD_SOCFPGA_KERNEL_COMPAT" to environment
> >   variable "socfpga_permodrst_ungate"
> >
> >  drivers/reset/reset-socfpga.c | 44 +++++++++++++++++++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> >
> > diff --git a/drivers/reset/reset-socfpga.c b/drivers/reset/reset-socfpga.c
> > index b2acfcd2ec..39d0b9e8f2 100644
> > --- a/drivers/reset/reset-socfpga.c
> > +++ b/drivers/reset/reset-socfpga.c
> > @@ -27,6 +27,36 @@ struct socfpga_reset_data {
> >       void __iomem *membase;
> >  };
> >
> > +/*
> > + * For compatibility with Kernels that don't support peripheral reset, this
> > + * driver can keep the old behaviour of not asserting peripheral reset before
> > + * starting the OS and deasserting all peripheral resets (enabling all
> > + * peripherals).
> > + *
> > + * For that, the reset driver checks the environment variable
> > + * "socfpga_legacy_reset_compat". If this variable is '1', perihperals are not
> > + * reset again once taken out of reset and all peripherals in 'permodrst' are
> > + * taken out of reset before booting into the OS.
> > + * Note that this should be required for gen5 systems only that are running
> > + * Linux kernels without proper peripheral reset support for all drivers used.
> > + */
> > +static bool socfpga_reset_keep_enabled(void)
> > +{
> > +#if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(ENV_SUPPORT)
> > +     const char *env_str;
> > +     long val;
> > +
> > +     env_str = env_get("socfpga_legacy_reset_compat");
> > +     if (env_str) {
> > +             val = simple_strtol(env_str, NULL, 0);
> > +             if (val == 1)
> > +                     return true;
> > +     }
> > +#endif
> > +
> > +     return false;
> > +}
> > +
> >  static int socfpga_reset_assert(struct reset_ctl *reset_ctl)
> >  {
> >       struct socfpga_reset_data *data = dev_get_priv(reset_ctl->dev);
> > @@ -89,6 +119,18 @@ static int socfpga_reset_probe(struct udevice *dev)
> >       return 0;
> >  }
> >
> > +static int socfpga_reset_remove(struct udevice *dev)
> > +{
> > +     struct socfpga_reset_data *data = dev_get_priv(dev);
> > +
> > +     if (socfpga_reset_keep_enabled()) {
> > +             puts("Deasserting all peripheral resets\n");
> > +             writel(0, data->membase + 4);
>
> Isn't permodreset at +0x14 ?

Yes it is. However, data->membase does not point to the actual base
address of the rstmgr but to the start of the "modrst" register group.

And permodreset is at offset 4 in this view.

While this looks a bit odd, it ensures the driver can be used for gen5
and a10 (and proably for s10 as well).

Regards,
Simon

>
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> >  static const struct udevice_id socfpga_reset_match[] = {
> >       { .compatible = "altr,rst-mgr" },
> >       { /* sentinel */ },
> > @@ -101,4 +143,6 @@ U_BOOT_DRIVER(socfpga_reset) = {
> >       .probe = socfpga_reset_probe,
> >       .priv_auto_alloc_size = sizeof(struct socfpga_reset_data),
> >       .ops = &socfpga_reset_ops,
> > +     .remove = socfpga_reset_remove,
> > +     .flags  = DM_FLAG_OS_PREPARE,
> >  };
> >
>
>
> --
> Best regards,
> Marek Vasut