[RFC PATCH v1 3/3] WIP: early: xhci-xdbc: Map lower and with 0 offset to partially work

[Umang Jain]

Map the area slightly lower than max fixmap. Detect the offset of xhci
xdbc cap and remap it again, so that the offset becomes 0.

----
>> This is investigation patch to get early xdbc attached to host
>> successfully. Without this, the xdbc doesn't attach to host.

on host:
[180056.895751] usb usb4-port2: attempt power cycle
[180059.049494] usb 4-2: Device not responding to setup address.
[180059.262513] usb 4-2: Device not responding to setup address.
[180059.463201] usb 4-2: device not accepting address 81, error -71
[180059.651391] usb 4-2: Device not responding to setup address.
[180059.862171] usb 4-2: Device not responding to setup address.
[180060.065072] usb 4-2: device not accepting address 82, error -71

on target:
[    5.779884] xhci_dbc:xdbc_start: waiting for device configuration timed out
[    5.779891] xhci_dbc:early_xdbc_setup_hardware: failed to setup the connection to host
----

This patches atleast makes the target attach to xhci host at
/dev/ttyUSB0. It's meant to debug and discuss the core issue as a
"clue".

Signed-off-by: Umang Jain <uajain@xxxxxxxxxx>
---
 drivers/usb/early/xhci-dbc.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 1f6a129d4b5d..b2bde2e8f85f 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -95,6 +95,9 @@ static void __iomem * __init xdbc_map_pci_mmio(u32 bus, u32 dev, u32 func)
 		return early_ioremap(val64, sz64);
 	}
 
+	/* Do not fill all fixed page slots in one go. */
+	fixmap_size = fixmap_size / 2;
+
 	/*
 	 * Base address size is greater than fixed size boot mappings,
 	 * hence iterate over the region one fixmap_size at a time.
@@ -110,6 +113,14 @@ static void __iomem * __init xdbc_map_pci_mmio(u32 bus, u32 dev, u32 func)
 				early_iounmap(base, fixmap_size);
 				base = early_ioremap(val64 + offset, XDBC_MAPPING_SIZE);
 			}
+
+			pr_notice("Found CAPS_DEBUG: mapped size: %llu, \
+				  fixmap_size: %llu, offset: %d, page_size:%d\n",
+				  mapped_size, fixmap_size, offset, 1 << PAGE_SHIFT);
+
+			early_iounmap(base, fixmap_size);
+			base = early_ioremap(val64+offset, fixmap_size);
+
 			break;
 		}
 
@@ -681,17 +692,7 @@ int __init early_xdbc_parse_parameter(char *s, int keep_early)
 	if (!xdbc.xhci_base)
 		return -EINVAL;
 
-	/* Locate DbC registers: */
-	offset = xhci_find_next_ext_cap(xdbc.xhci_base, 0, XHCI_EXT_CAPS_DEBUG);
-	if (!offset) {
-		pr_notice("xhci host doesn't support debug capability\n");
-		early_iounmap(xdbc.xhci_base, xdbc.xhci_base_length);
-		xdbc.xhci_base = NULL;
-		xdbc.xhci_base_length = 0;
-
-		return -ENODEV;
-	}
-	xdbc.xdbc_reg = (struct xdbc_regs __iomem *)(xdbc.xhci_base + offset);
+	xdbc.xdbc_reg = (struct xdbc_regs __iomem *)(xdbc.xhci_base);
 
 	return 0;
 }
-- 
2.53.0