[PATCH v3] reset: socfpga: Poll for reset status after deassert reset

[Ley Foon Tan]

In Cyclone 5 SoC platform, the first USB probing is failed but second
probing is success. DWC2 USB driver read gsnpsid register right after
de-assert reset, but controller is not ready yet and it returns gsnpsid 0.
Polling reset status after de-assert reset to solve the issue.

Retry with this fix more than 10 times without issue.

Signed-off-by: Ley Foon Tan <ley.foon.tan at intel.com>

---
v3:
- Remove _status callback and poll reset status after deassert reset

v2:
- https://patchwork.ozlabs.org/cover/1215174/

v1:
- https://patchwork.ozlabs.org/patch/1214841/
---
 drivers/reset/reset-socfpga.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/reset/reset-socfpga.c b/drivers/reset/reset-socfpga.c
index 93ec9cfdb6..172028dcf6 100644
--- a/drivers/reset/reset-socfpga.c
+++ b/drivers/reset/reset-socfpga.c
@@ -78,9 +78,20 @@ static int socfpga_reset_deassert(struct reset_ctl *reset_ctl)
 	int reg_width = sizeof(u32);
 	int bank = id / (reg_width * BITS_PER_BYTE);
 	int offset = id % (reg_width * BITS_PER_BYTE);
+	int i = 1000;
+	u32 status;
 
 	clrbits_le32(data->modrst_base + (bank * BANK_INCREMENT), BIT(offset));
-	return 0;
+
+	/* Poll until reset is completed. */
+	do {
+		status = readl(data->modrst_base + (bank * BANK_INCREMENT)) &
+			       BIT(offset);
+		if (!status)
+			return 0;
+	} while (i--);
+
+	return -ETIMEDOUT;
 }
 
 static int socfpga_reset_request(struct reset_ctl *reset_ctl)
-- 
2.19.0