linux-kernel - [PATCH 4.15 51/52] phy: phy-brcm-usb-init: DRD mode can cause crash on startup

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Date:   Mon, 19 Mar 2018 19:08:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Al Cooper <alcooperx@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Kishon Vijay Abraham I <kishon@...com>
Subject: [PATCH 4.15 51/52] phy: phy-brcm-usb-init: DRD mode can cause crash on startup

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Al Cooper <al.cooper@...adcom.com>

commit 0aa0c12262fd848c48448c39ff6c1c097be00dd4 upstream.

This is caused by a bug in the BDC core. When the BDC core comes
out of reset and it's not selected, it gets a backup clock. When
the BDC core is selected, it get's the main clock. If HOST mode
is then selected the BDC core has the main clock shut off but
the backup clock is not restored.

The failure scenario and cause are as follows:
- DRD mode is active
- Device mode is selected first in bootloader
- When host mode is now selected, the clock to the BDC is cut off.
- BDC registers are inaccessible and therefore the BDC driver
  crashes upon Linux boot.

The fix is to have the phy driver always force a BDC reset on
startup.

Fixes: 49859e55e364 ("phy: usb: phy-brcm-usb: Add Broadcom STB USB phy driver")
Signed-off-by: Al Cooper <alcooperx@...il.com>
Acked-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/phy/broadcom/phy-brcm-usb-init.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/phy/broadcom/phy-brcm-usb-init.c
+++ b/drivers/phy/broadcom/phy-brcm-usb-init.c
@@ -917,6 +917,7 @@ void brcm_usb_init_common(struct brcm_us
 			USB_CTRL_UNSET_FAMILY(params, USB_PM, BDC_SOFT_RESETB);
 			break;
 		default:
+			USB_CTRL_UNSET_FAMILY(params, USB_PM, BDC_SOFT_RESETB);
 			USB_CTRL_SET_FAMILY(params, USB_PM, BDC_SOFT_RESETB);
 		break;
 		}