[U-Boot] [PATCH v2 6/8] reset: socfpga: add reset handling for old kernels

[Simon Goldschmidt]

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 'remove' callback of this reset
driver, which is called on OS_PREPARE: it checks if the environment
variable "socfpga_permodrst_ungate" - if it is set to 1, it deasserts all
peripheral resets, 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 v2:
- moved from Kernel option "OLD_SOCFPGA_KERNEL_COMPAT" to environment
  variable "socfpga_permodrst_ungate"

 drivers/reset/reset-socfpga.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/drivers/reset/reset-socfpga.c b/drivers/reset/reset-socfpga.c
index b2acfcd2ec..749f671e05 100644
--- a/drivers/reset/reset-socfpga.c
+++ b/drivers/reset/reset-socfpga.c
@@ -89,6 +89,36 @@ static int socfpga_reset_probe(struct udevice *dev)
 	return 0;
 }
 
+#ifndef CONFIG_SPL_BUILD
+/*
+ * This remove function is called before starting OS to deassert peripheral
+ * resets for Kernels that don't support this.
+ *
+ * The reset driver checks the environment variable "socfpga_permodrst_ungate"
+ * when it is removed. If this variable is '1', all peripherals in 'permodrst'
+ * are taken out of reset before booting into the OS.
+ * This should be required for gen5 systems only that are running Linux kernels
+ * without proper peripheral reset support for all drivers used.
+ */
+static int socfpga_reset_remove(struct udevice *dev)
+{
+	struct socfpga_reset_data *data = dev_get_priv(dev);
+	const char *env_str;
+	long val;
+
+	env_str = env_get("socfpga_permodrst_ungate");
+	if (env_str) {
+		val = simple_strtol(env_str, NULL, 0);
+		if (val == 1) {
+			puts("Deasserting all peripheral resets\n");
+			writel(0, data->membase + 4);
+		}
+	}
+
+	return 0;
+}
+#endif
+
 static const struct udevice_id socfpga_reset_match[] = {
 	{ .compatible = "altr,rst-mgr" },
 	{ /* sentinel */ },
@@ -101,4 +131,8 @@ U_BOOT_DRIVER(socfpga_reset) = {
 	.probe = socfpga_reset_probe,
 	.priv_auto_alloc_size = sizeof(struct socfpga_reset_data),
 	.ops = &socfpga_reset_ops,
+#ifndef CONFIG_SPL_BUILD
+	.remove = socfpga_reset_remove,
+	.flags	= DM_FLAG_OS_PREPARE,
+#endif
 };
-- 
2.17.1