[PATCH v3 2/6] usb: ehci: add port reset hooks

[Linus Walleij <linusw@kernel.org>]

Some EHCI implementations need controller-specific sequencing around
port reset.

Add optional hooks for reset preparation and completion. Controllers
without the hooks retain the existing behavior.

Gate the callbacks behind the hidden USB_EHCI_PORT_RESET_HOOKS option
so controllers using standard reset sequencing incur no extra state or
runtime checks.

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Suggested-by: Daniel Palmer <daniel@thingy.jp>
Assisted-by: LLM
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 drivers/usb/host/Kconfig    |  4 ++++
 drivers/usb/host/ehci-hub.c | 16 ++++++++++++++++
 drivers/usb/host/ehci.h     |  6 ++++++
 3 files changed, 26 insertions(+)

diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
index af4fc14b8783..a0c66191d03c 100644
--- a/drivers/usb/host/Kconfig
+++ b/drivers/usb/host/Kconfig
@@ -215,6 +215,10 @@ config USB_EHCI_DEVIANT_PORT_STATUS_REG
 	bool
 	# Used for hosts with a deviant port status register location
 
+config USB_EHCI_PORT_RESET_HOOKS
+	bool
+	# Used for hosts with controller-specific port reset sequencing
+
 config XPS_USB_HCD_XILINX
 	bool "Use Xilinx usb host EHCI controller core"
 	depends on (PPC32 || MICROBLAZE)
diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c
index 77d0df41f45f..5aa629a92542 100644
--- a/drivers/usb/host/ehci-hub.c
+++ b/drivers/usb/host/ehci-hub.c
@@ -963,6 +963,13 @@ int ehci_hub_control(
 			/* see what we found out */
 			temp = check_reset_complete (ehci, wIndex, status_reg,
 					ehci_readl(ehci, status_reg));
+#ifdef CONFIG_USB_EHCI_PORT_RESET_HOOKS
+			if (ehci->post_port_reset) {
+				retval = ehci->post_port_reset(ehci, wIndex);
+				if (retval)
+					goto error_exit;
+			}
+#endif
 		}
 
 		/* transfer dedicated ports to the companion hc */
@@ -1121,7 +1128,16 @@ int ehci_hub_control(
 				 */
 				if (ehci_has_fsl_hs_errata(ehci))
 					temp |= (1 << PORTSC_FSL_PFSC);
+
+#ifdef CONFIG_USB_EHCI_PORT_RESET_HOOKS
+				if (ehci->pre_port_reset) {
+					retval = ehci->pre_port_reset(ehci, wIndex);
+					if (retval)
+						goto error_exit;
+				}
+#endif
 			}
+
 			ehci_writel(ehci, temp, status_reg);
 			break;
 
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index a65fba092e76..d7e4cd6dc0a3 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -126,6 +126,12 @@ struct ehci_hcd {			/* one per controller */
 #ifdef CONFIG_USB_EHCI_DEVIANT_PORT_STATUS_REG
 	u32 __iomem		*port_status;
 #endif
+#ifdef CONFIG_USB_EHCI_PORT_RESET_HOOKS
+	int			(*pre_port_reset)(struct ehci_hcd *ehci,
+						  unsigned int port);
+	int			(*post_port_reset)(struct ehci_hcd *ehci,
+						   unsigned int port);
+#endif
 
 	__u32			hcs_params;	/* cached register copy */
 	spinlock_t		lock;

-- 
2.55.0