On Fri, Dec 17, 2021 at 04:19:20PM +0100, Greg KH wrote:
> On Fri, Dec 17, 2021 at 02:55:07PM +0100, Peter Zijlstra wrote:
> > On Fri, Dec 17, 2021 at 01:01:43PM +0200, Mathias Nyman wrote:
> > > I can reproduce this.
> > > Looks like problems started when driver converted to readl_poll_timeout_atomic() in:
> > >
> > > 796eed4b2342 usb: early: convert to readl_poll_timeout_atomic()
> >
> > I can confirm, reverting that solves the boot hang, things aren't quite
> > working for me though.
> >
> > > Seems to hang when read_poll_timeout_atomic() calls ktime_* functions.
> > > Maybe it's too early for ktime.
> >
> > It certainly is, using ktime for delay loops sounds daft to me anyhow.
>
> It was a "find a pattern and replace it with a function call" type of
> cleanup series. It's obviously wrong, I will go revert it now.
796eed4b2342 is definitely wrong, but instead of a straight up revert,
perhaps do something like this ?
---
Subject: usb: early: Revert from readl_poll_timeout_atomic()
Reverts commit 796eed4b2342 ("usb: early: convert to
readl_poll_timeout_atomic()") and puts in a comment to avoid the same
happening again.
Specifically that commit is wrong because readl_poll_timeout_atomic()
relies on ktime() working while this earlyprintk driver should be usable
long before that.
Fixes: 796eed4b2342 ("usb: early: convert to readl_poll_timeout_atomic()")
Debugged-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
drivers/usb/early/xhci-dbc.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index 933d77ad0a64..ff279a830653 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -14,7 +14,6 @@
#include <linux/pci_ids.h>
#include <linux/memblock.h>
#include <linux/io.h>
-#include <linux/iopoll.h>
#include <asm/pci-direct.h>
#include <asm/fixmap.h>
#include <linux/bcd.h>
@@ -136,9 +135,20 @@ static int handshake(void __iomem *ptr, u32 mask, u32 done, int wait, int delay)
{
u32 result;
- return readl_poll_timeout_atomic(ptr, result,
- ((result & mask) == done),
- delay, wait);
+ /*
+ * This must not be readl_poll_timeout_atomic(), as this is used
+ * *early*, before ktime lives.
+ */
+ do {
+ result = readl(ptr);
+ result &= mask;
+ if (result == done)
+ return 0;
+ udelay(delay);
+ wait -= delay;
+ } while (wait > 0);
+
+ return -ETIMEDOUT;
}
static void __init xdbc_bios_handoff(void)
