All of lore.kernel.org
 help / color / mirror / Atom feed
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
To: Ezequiel Garcia <ezequiel@collabora.com>
Cc: "Matwey V. Kornilov" <matwey@sai.msu.ru>,
	Alan Stern <stern@rowland.harvard.edu>,
	Hans de Goede <hdegoede@redhat.com>,
	hverkuil@xs4all.nl, mchehab@kernel.org,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	rostedt@goodmis.org, mingo@redhat.com, isely@pobox.com,
	bhumirks@gmail.com, colin.king@canonical.com,
	linux-media@vger.kernel.org,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer
Date: Mon, 30 Jul 2018 13:07:02 -0300	[thread overview]
Message-ID: <20180730130702.27664d15@coco.lan> (raw)
In-Reply-To: <eb2b495fe7e8bbeaf3f9e2814be4923583482852.camel@collabora.com>

Em Tue, 17 Jul 2018 17:10:22 -0300
Ezequiel Garcia <ezequiel@collabora.com> escreveu:

> Yeah, and not setting URB_NO_TRANSFER_DMA_MAP makes the USB core
> create DMA mappings and use the streaming API. Which makes more
> sense in hardware without hardware coherency.
>
> The only thing that bothers me with this patch is that it's not
> really something specific to this driver. If this fix is valid
> for pwc, then it's valid for all the drivers allocating coherent
> memory.

We're actually doing this change on other drivers:
	https://git.linuxtv.org/media_tree.git/commit/?id=d571b592c6206

I suspect that the reason why all USB media drivers were using
URB_NO_TRANSFER_DMA_MAP is just because the first media USB driver
upstream used it.

On that time, I remember I tried once to not use this flag, but there
was something that broke (perhaps I just didn't know enough about the
USB layer - or perhaps some fixes happened at USB core - allowing it
to be used with ISOC transfers).

Anyway, nowadays, I fail to see a reason why not let the USB core
do the DMA maps. On my tests after this patch, at the boards I tested
(arm and x86), I was unable to see any regressions.

Thanks,
Mauro

  parent reply	other threads:[~2018-07-30 17:43 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-17 14:36 [PATCH 1/2] Add TRACE_EVENTs in pwc_isoc_handler() Matwey V. Kornilov
2018-06-17 14:36 ` [PATCH 2/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer Matwey V. Kornilov
2018-06-18  5:11   ` Ezequiel Garcia
2018-06-18  7:10     ` Matwey V. Kornilov
2018-07-17 20:10       ` Ezequiel Garcia
2018-07-17 20:51         ` Alan Stern
2018-07-20 10:55           ` Tomasz Figa
2018-07-20 11:22             ` Matwey V. Kornilov
2018-07-20 11:33               ` Tomasz Figa
2018-07-20 11:57                 ` Matwey V. Kornilov
2018-07-23 17:04                   ` Matwey V. Kornilov
2018-07-23 18:57                     ` Alan Stern
2018-07-24 18:56                       ` Matwey V. Kornilov
2018-07-24 20:55                         ` Alan Stern
2018-07-25 13:46                           ` Matwey V. Kornilov
2018-07-30  4:14                             ` Tomasz Figa
2018-08-04  8:05                               ` Matwey V. Kornilov
2018-07-30 15:35                         ` Laurent Pinchart
2018-08-04  8:00                           ` Matwey V. Kornilov
2018-08-04 14:46                             ` Alan Stern
2018-08-05  7:49                               ` Christoph Hellwig
2018-08-05  8:33                                 ` Matwey V. Kornilov
2018-08-05  8:41                                   ` Christoph Hellwig
2018-08-08 22:32                             ` Laurent Pinchart
2018-08-09  2:36                               ` Tomasz Figa
2018-08-09 10:28                                 ` Laurent Pinchart
2018-07-30 15:13                 ` Laurent Pinchart
2018-07-18 12:10         ` Matwey V. Kornilov
2018-07-19 23:36           ` Ezequiel Garcia
2018-07-20  9:35             ` Matwey V. Kornilov
2018-07-30 15:42             ` Laurent Pinchart
2018-07-30 16:07         ` Mauro Carvalho Chehab [this message]
2018-07-31  6:06           ` Tomasz Figa
2018-06-18 18:58 ` [PATCH 1/2] Add TRACE_EVENTs in pwc_isoc_handler() Steven Rostedt
2018-06-19 16:23   ` Matwey V. Kornilov
2018-06-19 16:33     ` Steven Rostedt
2018-06-20  8:05       ` Matwey V. Kornilov
2018-06-20 13:09         ` Steven Rostedt

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=20180730130702.27664d15@coco.lan \
    --to=mchehab+samsung@kernel.org \
    --cc=bhumirks@gmail.com \
    --cc=colin.king@canonical.com \
    --cc=ezequiel@collabora.com \
    --cc=hdegoede@redhat.com \
    --cc=hverkuil@xs4all.nl \
    --cc=isely@pobox.com \
    --cc=laurent.pinchart@ideasonboard.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=matwey@sai.msu.ru \
    --cc=mchehab@kernel.org \
    --cc=mingo@redhat.com \
    --cc=rostedt@goodmis.org \
    --cc=stern@rowland.harvard.edu \
    /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.