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

[Marek Vasut]

On 3/1/19 1:14 PM, Simon Goldschmidt wrote:
> 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).
> 

Some comment explaining this would be nice :)

-- 
Best regards,
Marek Vasut