From: Felipe Balbi <felipe.balbi@linux.intel.com>
To: Pawel Laszczak <pawell@cadence.com>,
"devicetree\@vger.kernel.org" <devicetree@vger.kernel.org>
Cc: "gregkh\@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"linux-usb\@vger.kernel.org" <linux-usb@vger.kernel.org>,
"hdegoede\@redhat.com" <hdegoede@redhat.com>,
"heikki.krogerus\@linux.intel.com"
<heikki.krogerus@linux.intel.com>,
"robh+dt\@kernel.org" <robh+dt@kernel.org>,
"rogerq\@ti.com" <rogerq@ti.com>,
"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"jbergsagel\@ti.com" <jbergsagel@ti.com>,
"nsekhar\@ti.com" <nsekhar@ti.com>, "nm\@ti.com" <nm@ti.com>,
Suresh Punnoose <sureshp@cadence.com>,
"peter.chen\@nxp.com" <peter.chen@nxp.com>,
Jayshri Dajiram Pawar <jpawar@cadence.com>,
Rahul Kumar <kurahul@cadence.com>
Subject: RE: [PATCH v9 5/6] usb:cdns3 Add Cadence USB3 DRD Driver
Date: Mon, 12 Aug 2019 12:45:30 +0300 [thread overview]
Message-ID: <87d0hau37p.fsf@gmail.com> (raw)
In-Reply-To: <BYAPR07MB4709C07ED94C952886858F14DDD30@BYAPR07MB4709.namprd07.prod.outlook.com>
[-- Attachment #1: Type: text/plain, Size: 3750 bytes --]
Hi,
Pawel Laszczak <pawell@cadence.com> writes:
>>>>>>Quick question, then: these ISTS registers, are they masked interrupt
>>>>>>status or raw interrupt status?
>>>>>
>>>>> Yes it's masked, but after masking them the new interrupts will not be reported
>>>>> In ISTS registers. Form this reason I can mask only reported interrupt.
>>>>
>>>>and what happens when you unmask the registers? Do they get reported?
>>>
>>> No they are not reported in case of USB_ISTS register.
>>> They should be reported in case EP_ISTS, but I need to test it.
>>
>>okay, please _do_ test and verify the behavior. The description above
>>sounds really surprising to me. Does it really mean that if you mask all
>>USB_ISTS and then disconnect the cable while interrupt is masked, you
>>won't know cable was disconnected?
>
> Yes, exactly.
>
> Initially I've tested it and it's work correct.
> I can even simply write 0 to EP_IEN in hard irq and ~0 in thread handler.
> It's simplest and sufficient way.
okay. Just to be sure I understand correctly. If you mask USB_IEN, then
we would miss a cable disconnect event. Right?
>>>>>>>>> + struct cdns3_aligned_buf *buf, *tmp;
>>>>>>>>> +
>>>>>>>>> + list_for_each_entry_safe(buf, tmp, &priv_dev->aligned_buf_list,
>>>>>>>>> + list) {
>>>>>>>>> + if (!buf->in_use) {
>>>>>>>>> + list_del(&buf->list);
>>>>>>>>> +
>>>>>>>>> + spin_unlock_irqrestore(&priv_dev->lock, flags);
>>>>>>>>
>>>>>>>>creates the possibility of a race condition
>>>>>>> Why? In this place the buf can't be used.
>>>>>>
>>>>>>but you're reenabling interrupts, right?
>>>>>
>>>>> Yes, driver frees not used buffers here.
>>>>> I think that it's the safest place for this purpose.
>>>>
>>>>I guess you missed the point a little. Since you reenable interrupts
>>>>just to free the buffer, you end up creating the possibility for a race
>>>>condition. Specially since you don't mask all interrupt events. The
>>>>moment you reenable interrupts, one of your not-unmasked interrupt
>>>>sources could trigger, then top-half gets scheduled which tries to wake
>>>>up the IRQ thread again and things go boom.
>>>
>>> Ok, I think I understand. So I have 3 options:
>>> 1. Mask the USB_IEN and EP_IEN interrupts, but then I can lost some USB_ISTS
>>> events. It's dangerous options.
>>
>>sure sounds dangerous, but also sounds quite "peculiar" :-)
>>
>>> 2. Remove implementation of handling unaligned buffers and assume that
>>> upper layer will worry about this. What with vendor specific drivers that
>>> can be used by companies and not upstreamed ?
>>> It could be good to have such safety mechanism even if it is not currently used.
>>
>>dunno. It may become dead code that's NEVER used :-)
>>
>>> 3. Delegate this part of code for instance to separate thread that will be called
>>> In free time.
>>
>>Yet another thread? Can't you just run this right before giving back the
>>USB request? So, don't do it from IRQ handler, but from giveback path?
>
> Do you mean in:
> if (request->complete) {
> spin_unlock(&priv_dev->lock);
> if (priv_dev->run_garbage_collector) {
> ....
> }
> usb_gadget_giveback_request(&priv_ep->endpoint,
> request);
> spin_lock(&priv_dev->lock);
> }
> ??
right, you can do it right before giving back the request. Or right
after.
> I ask because this is finally also called from IRQ handler:
>
> cdns3_device_thread_irq_handler
> -> cdns3_check_ep_interrupt_proceed
> -> cdns3_transfer_completed
> -> cdns3_gadget_giveback
> -> usb_gadget_giveback_request
Did you notice that it doesn't reenable interrupts, though?
--
balbi
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 832 bytes --]
next prev parent reply other threads:[~2019-08-12 9:45 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-05 10:57 [PATCH v9 0/6] Introduced new Cadence USBSS DRD Driver Pawel Laszczak
2019-07-05 10:57 ` [PATCH v9 1/6] dt-bindings: add binding for USBSS-DRD controller Pawel Laszczak
2019-07-05 10:57 ` [PATCH v9 2/6] usb:gadget Separated decoding functions from dwc3 driver Pawel Laszczak
2019-07-05 11:27 ` Greg KH
2019-07-05 11:39 ` Pawel Laszczak
2019-07-05 11:49 ` Greg KH
2019-07-05 12:03 ` Pawel Laszczak
2019-07-05 11:39 ` Felipe Balbi
2019-07-05 11:44 ` Pawel Laszczak
2019-08-07 10:17 ` Roger Quadros
2019-08-07 10:22 ` Felipe Balbi
2019-08-08 3:07 ` Pawel Laszczak
2019-07-05 10:57 ` [PATCH v9 3/6] usb:gadget Patch simplify usb_decode_set_clear_feature function Pawel Laszczak
2019-07-05 10:57 ` [PATCH v9 4/6] usb:gadget Simplify usb_decode_get_set_descriptor function Pawel Laszczak
2019-07-05 10:57 ` [PATCH v9 5/6] usb:cdns3 Add Cadence USB3 DRD Driver Pawel Laszczak
2019-07-05 11:55 ` Felipe Balbi
2019-07-07 17:56 ` Pawel Laszczak
2019-07-08 6:29 ` Felipe Balbi
2019-07-08 10:59 ` Pawel Laszczak
2019-07-08 11:15 ` Felipe Balbi
2019-07-08 11:45 ` Pawel Laszczak
2019-07-08 11:59 ` Felipe Balbi
2019-07-08 12:39 ` Pawel Laszczak
2019-07-09 4:23 ` Pawel Laszczak
2019-07-09 6:36 ` Felipe Balbi
2019-07-09 7:07 ` Pawel Laszczak
2019-07-09 7:22 ` Felipe Balbi
2019-07-09 7:29 ` Pawel Laszczak
2019-07-10 8:25 ` Pawel Laszczak
2019-07-08 7:11 ` Felipe Balbi
2019-07-15 11:00 ` Pawel Laszczak
2019-08-07 10:34 ` Felipe Balbi
2019-08-10 20:39 ` Pawel Laszczak
2019-08-12 1:55 ` Peter Chen
2019-08-12 4:43 ` Pawel Laszczak
2019-08-12 5:24 ` Felipe Balbi
2019-08-12 7:13 ` Pawel Laszczak
2019-08-12 8:19 ` Felipe Balbi
2019-08-12 9:13 ` Pawel Laszczak
2019-08-12 9:45 ` Felipe Balbi [this message]
2019-08-12 10:26 ` Pawel Laszczak
2019-08-12 10:34 ` Felipe Balbi
2019-08-12 14:20 ` Alan Stern
2019-07-05 10:57 ` [PATCH v9 6/6] usb:cdns3 Fix for stuck packets in on-chip OUT buffer Pawel Laszczak
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87d0hau37p.fsf@gmail.com \
--to=felipe.balbi@linux.intel.com \
--cc=devicetree@vger.kernel.org \
--cc=gregkh@linuxfoundation.org \
--cc=hdegoede@redhat.com \
--cc=heikki.krogerus@linux.intel.com \
--cc=jbergsagel@ti.com \
--cc=jpawar@cadence.com \
--cc=kurahul@cadence.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=nm@ti.com \
--cc=nsekhar@ti.com \
--cc=pawell@cadence.com \
--cc=peter.chen@nxp.com \
--cc=robh+dt@kernel.org \
--cc=rogerq@ti.com \
--cc=sureshp@cadence.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).