[PATCH v2] usb: cdns3: gadget.c: Set fast access bit

[Ravi Gunasekaran]

From: Aswath Govindraju <a-govindraju at ti.com>

When the device port is in a low power state [U3/L2/Not Connected],
accesses to usb device registers may take a long time. This could lead to
potential core hang when the controller registers are accessed after the
port is disabled by setting DEVDS field. Setting the fast register access
bit ensures that the PHY clock is keeping up in active state.

Therefore, set fast access bit to ensure the accesses to device registers
are quick even in low power states.

Signed-off-by: Aswath Govindraju <a-govindraju at ti.com>
Signed-off-by: Ravi Gunasekaran <r-gunasekaran at ti.com>
Reviewed-by: Roger Quadros <rogerq at kernel.org>
---
v1 was posted and was reviewed as well. But it did not get merged.
This change is present in upstream linux kernel as well.
Upstream Linux kernel commit: b5148d946f45 ("usb: cdns3: gadget: set fast access bit")

Changes since v1:
----------------
* Rebased to tip of -next
* Added Reviewed-by tag

v1: https://lore.kernel.org/u-boot/20230505121353.23486-1-r-gunasekaran@ti.com/

 drivers/usb/cdns3/gadget.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
index 7aa0c6b2be..d11175dc5b 100644
--- a/drivers/usb/cdns3/gadget.c
+++ b/drivers/usb/cdns3/gadget.c
@@ -2325,6 +2325,9 @@ static void cdns3_gadget_config(struct cdns3_device *priv_dev)
 	writel(USB_IEN_INIT, &regs->usb_ien);
 	writel(USB_CONF_CLK2OFFDS | USB_CONF_L1DS, &regs->usb_conf);
 
+	/* Set the Fast access bit */
+	writel(PUSB_PWR_FST_REG_ACCESS, &priv_dev->regs->usb_pwr);
+
 	cdns3_configure_dmult(priv_dev, NULL);
 
 	cdns3_gadget_pullup(&priv_dev->gadget, 1);
@@ -2383,6 +2386,7 @@ static int cdns3_gadget_udc_stop(struct usb_gadget *gadget)
 
 	/* disable interrupt for device */
 	writel(0, &priv_dev->regs->usb_ien);
+	writel(0, &priv_dev->regs->usb_pwr);
 	writel(USB_CONF_DEVDS, &priv_dev->regs->usb_conf);
 
 	return ret;

base-commit: bc39e06778168a34bb4e0a34fbee4edbde4414d8
-- 
2.17.1