Re: earlyprintk=xdbc seems broken

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Jan 25, 2022 at 10:51:00AM +0200, Mathias Nyman wrote:
> On 24.1.2022 18.46, Peter Zijlstra wrote:

> > FYI, I'm thinking early_xdbc_parse_parameter should've now given
> > dpgp_num: 1 ?
> > 
> 
> Yes, it should. 
> 
> Looks like there's a parsing issue.
> "earlyprintk=xdbc1,keep" fails on our Tigerlake as well.
>   
> Without the "keep" option it works for me:
> 
> [    0.000000] Command line: console=ttyS0,115200n8 buildroot_hostname=tgl04 earlyprintk=xdbc1 dmi_entry_point=0x74374000
> [    0.000000] xhci_dbc:early_xdbc_parse_parameter: dbgp_num: 1

[    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.16.0+ root=UUID=a652986c-fbc6-4341-85c3-b4ad4402f130 ro debug ignore_loglevel sysrq_always_enabled usbcore.autosuspend=-1 earlyprintk=xdbc1,keep force_early_printk sched_verbose ft
race=nop mitigations=off nokaslr

[    0.000000] xhci_dbc:early_xdbc_parse_parameter: dbgp_num: 1

[    0.399988] xhci_dbc:xdbc_start: DbC is running now, control 0x8d000003 port ID 15
[    0.399998] xhci_dbc:xdbc_handle_port_status: connect status change event
[    0.399999] xhci_dbc:xdbc_handle_port_status: port reset change event
[    0.431217] printk: console [earlyxdbc0] enabled

Success!! I'll go submit proper patches for this then.

---

diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index d3c531d3b244..68b38925a74f 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -387,7 +387,7 @@ static int __init setup_early_printk(char *buf)
 #endif
 #ifdef CONFIG_EARLY_PRINTK_USB_XDBC
 		if (!strncmp(buf, "xdbc", 4))
-			early_xdbc_parse_parameter(buf + 4);
+			early_xdbc_parse_parameter(buf + 4, keep);
 #endif
 
 		buf++;
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index a698196377be..9bf3872895ab 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1505,6 +1505,7 @@ void __init tsc_early_init(void)
 	loops_per_jiffy = get_loops_per_jiffy();
 
 	tsc_enable_sched_clock();
+	use_tsc_delay();
 }
 
 void __init tsc_init(void)
diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 4502108069cd..a40db9618e8e 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -29,11 +29,15 @@
 static struct xdbc_state xdbc;
 static bool early_console_keep;
 
+#if 0
 #ifdef XDBC_TRACE
 #define	xdbc_trace	trace_printk
 #else
 static inline void xdbc_trace(const char *fmt, ...) { }
 #endif /* XDBC_TRACE */
+#else
+#define xdbc_trace	pr_err
+#endif
 
 static void __iomem * __init xdbc_map_pci_mmio(u32 bus, u32 dev, u32 func)
 {
@@ -417,9 +421,11 @@ static void xdbc_ring_doorbell(int target)
 
 static int xdbc_start(void)
 {
+	bool first_try = true;
 	u32 ctrl, status;
 	int ret;
 
+retry:
 	ctrl = readl(&xdbc.xdbc_reg->control);
 	writel(ctrl | CTRL_DBC_ENABLE | CTRL_PORT_ENABLE, &xdbc.xdbc_reg->control);
 	ret = handshake(&xdbc.xdbc_reg->control, CTRL_DBC_ENABLE, CTRL_DBC_ENABLE, 100000, 100);
@@ -429,13 +435,21 @@ static int xdbc_start(void)
 	}
 
 	/* Reset port to avoid bus hang: */
-	if (xdbc.vendor == PCI_VENDOR_ID_INTEL)
+	if (xdbc.vendor == PCI_VENDOR_ID_INTEL && first_try)
 		xdbc_reset_debug_port();
 
 	/* Wait for port connection: */
 	ret = handshake(&xdbc.xdbc_reg->portsc, PORTSC_CONN_STATUS, PORTSC_CONN_STATUS, 5000000, 100);
 	if (ret) {
-		xdbc_trace("waiting for connection timed out\n");
+		xdbc_trace("waiting for connection timed out, DCPORTSC:0x%x\n",
+				readl(&xdbc.xdbc_reg->portsc));
+		if (first_try) {
+			first_try = false;
+			/* Toggle DCE and retry without port reset */
+			writel(0, &xdbc.xdbc_reg->control);
+			handshake(&xdbc.xdbc_reg->control, CTRL_DBC_ENABLE, 0, 100000, 10);
+			goto retry;
+		}
 		return ret;
 	}
 
@@ -599,23 +631,26 @@ static int __init xdbc_early_setup(void)
 	return 0;
 }
 
-int __init early_xdbc_parse_parameter(char *s)
+int __init early_xdbc_parse_parameter(char *s, int keep_early)
 {
 	unsigned long dbgp_num = 0;
 	u32 bus, dev, func, offset;
+	char *e;
 	int ret;
 
 	if (!early_pci_allowed())
 		return -EPERM;
 
-	if (strstr(s, "keep"))
-		early_console_keep = true;
+	early_console_keep = keep_early;
 
 	if (xdbc.xdbc_reg)
 		return 0;
 
-	if (*s && kstrtoul(s, 0, &dbgp_num))
-		dbgp_num = 0;
+	if (*s) {
+	       dbgp_num = simple_strtoul(s, &e, 10);
+	       if (s == e)
+		       dbgp_num = 0;
+	}
 
 	pr_notice("dbgp_num: %lu\n", dbgp_num);
 
diff --git a/include/linux/usb/xhci-dbgp.h b/include/linux/usb/xhci-dbgp.h
index 0a37f1283bf0..01fe768873f9 100644
--- a/include/linux/usb/xhci-dbgp.h
+++ b/include/linux/usb/xhci-dbgp.h
@@ -15,7 +15,7 @@
 #define __LINUX_XHCI_DBGP_H
 
 #ifdef CONFIG_EARLY_PRINTK_USB_XDBC
-int __init early_xdbc_parse_parameter(char *s);
+int __init early_xdbc_parse_parameter(char *s, int keep_early);
 int __init early_xdbc_setup_hardware(void);
 void __init early_xdbc_register_console(void);
 #else