From: Michal Pecio <michal.pecio@gmail.com>
To: David Laight <david.laight.linux@gmail.com>
Cc: Xincheng Zhang <zhangxincheng@ultrarisc.com>,
cyrozap@gmail.com, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
mathias.nyman@intel.com
Subject: Re: [PATCH] usb: xhci-pci: Disable 64-bit DMA for VIA VL805
Date: Fri, 26 Jun 2026 10:57:23 +0200 [thread overview]
Message-ID: <20260626105723.42972329.michal.pecio@gmail.com> (raw)
In-Reply-To: <20260626090615.616666b4@pumpkin>
On Fri, 26 Jun 2026 09:06:15 +0100, David Laight wrote:
> Can you do a read-back of one of the control registers that contains
> an address - if you are lucky the high bits will return zero.
> That might let the generic code enforce a limit.
Interesting idea, but nope. My VL805 with 36 bit 013600 firmware
is set up with 37 bit DMA mask right now. MMIO registers read:
DCBAAP_LOW = 0xffffe000
DCBAAP_HIGH = 0x0000001f
IR0_ERSTBA_LOW = 0xfffee000
IR0_ERSTBA_HIGH = 0x0000001f
IR0_ERDP_LOW = 0xffff4018
IR0_ERDP_HIGH = 0x0000001f
Nothing hints that the chip will truncate this to 36 bits when
DMA-ing. We learn about it when it happens.
Regards,
Michal
next prev parent reply other threads:[~2026-06-26 8:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-23 7:32 [PATCH] usb: xhci-pci: Disable 64-bit DMA for VIA VL805 Xincheng Zhang
2026-06-23 10:18 ` Michal Pecio
2026-06-24 5:26 ` Xincheng Zhang
2026-06-24 7:06 ` Xincheng Zhang
2026-06-25 0:04 ` Michal Pecio
2026-06-25 2:16 ` Xincheng Zhang
2026-06-25 17:18 ` Michal Pecio
2026-06-26 2:08 ` Xincheng Zhang
2026-06-26 8:06 ` David Laight
2026-06-26 8:57 ` Michal Pecio [this message]
2026-06-26 10:55 ` David Laight
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=20260626105723.42972329.michal.pecio@gmail.com \
--to=michal.pecio@gmail.com \
--cc=cyrozap@gmail.com \
--cc=david.laight.linux@gmail.com \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=mathias.nyman@intel.com \
--cc=zhangxincheng@ultrarisc.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.