On 13.12.2013 13:34, Grazvydas Ignotas wrote:
On Thu, Dec 12, 2013 at 11:29 PM, Andreas Naumann <dev@xxxxxxxx> wrote:
Hi Grazvydas,
Von: Grazvydas Ignotas [mailto:notasas@xxxxxxxxx]
Gesendet: Donnerstag, 12. Dezember 2013 01:21
An: linux-usb@xxxxxxxxxxxxxxx
Cc: Felipe Balbi; linux-omap@xxxxxxxxxxxxxxx; Naumann Andreas; Grazvydas
Ignotas; stable@xxxxxxxxxxxxxxx
Betreff: [PATCH] usb: musb: omap2430: fix occasional musb breakage on boot
This is a hard to reproduce problem which leads to non-functional
USB-OTG port in 0.1%-1% of all boots. Tracked it down to commit
e25bec160158abe86c "omap2+: save and restore OTG_INTERFSEL",
which introduces save/restore of OTG_INTERFSEL over suspend.
Since the resume function is also called early in driver init, it uses a
non-initialized value (which is 0 and a non-supported setting in DM37xx
for INTERFSEL). Shortly after the correct value is set. Apparently this
works most time, but not always.
Fix it by not writing the value on runtime resume if it is 0
(0 should never be saved in the context as it's invalid value,
so we use it as an indicator that context hasn't been saved yet).
This issue was originally found by Andreas Naumann:
http://marc.info/?l=linux-usb&m=138562574719654&w=2
Reported-and-bisected-by: Andreas Naumann <anaumann@xxxxxxxxxxxxxx>
Signed-off-by: Grazvydas Ignotas <notasas@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
This is a regression from 3.2, so should go to -rc and stable, IMO.
It's really annoying issue if you want to have a stable OTG behavior,
I've burned quite a lot of time on it myself over a year ago and gave up
eventually. Good thing Andreas finally found it, many thanks to him!
drivers/usb/musb/omap2430.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/musb/omap2430.c b/drivers/usb/musb/omap2430.c
index 2a408cd..737b3da 100644
--- a/drivers/usb/musb/omap2430.c
+++ b/drivers/usb/musb/omap2430.c
@@ -672,7 +672,8 @@ static int omap2430_runtime_resume(struct device *dev)
if (musb) {
omap2430_low_level_init(musb);
- musb_writel(musb->mregs, OTG_INTERFSEL,
+ if (musb->context.otg_interfsel != 0)
+ musb_writel(musb->mregs, OTG_INTERFSEL,
musb->context.otg_interfsel);
phy_power_on(musb->phy);
}
Oh, easy way out. I like it but I've also been thinking about your comment
on my original post, which was that initializing otg_interfsel to the PHYSEL
bits only might be dangerous because we cant be sure that there are other
bits in the register.
However, isnt assuming that 0 is invalid on all OMAPs just as dangerous?
Well I was trying to do a minimal fix so that it could be suitable for
merging to stable kernels. But yes you're right, I've just checked
OMAP4 TRM and 0 is actually valid value there..
After thinking about my patch again, I would propose to change otg_interfsel
into otg_physel and read-modify-write only those bits in resume() as you
suggested in your first answer. That way I could discard the problematic
first read in probe() while leaving other bits untouched. If you agree I
post a patch for this tomorrow.
Hmm I don't know about that, this would be inconsistent with what all
other OMAP drivers do. Maybe we should do what musb_core.c does just
Ok, thats cool.
to be consistent and add a similar comment. Only the static variable
could be avoided in favor of struct omap2430_glue member.
Whats wrong with the static?
cheers,
Andreas
Gražvydas
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