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

[Marek Vasut]

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 ?

> +	}
> +
> +	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