linux-kernel - [PATCH 0/6] vme: DMA improvements

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Date:	Mon, 18 May 2015 21:56:27 +0300
From:	Dmitry Kalinkin <dmitry.kalinkin@...il.com>
To:	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org
Cc:	Martyn Welch <martyn.welch@...com>,
	Manohar Vanga <manohar.vanga@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Igor Alekseev <igor.alekseev@...p.ru>,
	Dmitry Kalinkin <dmitry.kalinkin@...il.com>
Subject: [PATCH 0/6] vme: DMA improvements

The first item in this submission documents previously introduced
vme_master_mmap() call. Following, there are three fixes for the tsi148
driver's DMA.  There was one bug that rendered it imposible to use DMA
lists with more than one item. The other was related to the place where
dma_map_single was called on the first DMA descriptor in the DMA list. The
last bug was about DMA transfer not stopping at interruption by signal,
which is a possible DoS attack vector. I also made an attempt to fix the
same issue in the ca91cx42 driver. I don't have access to this hardware to
test, so this is based only on my understanding of the datasheet (checked
ca91c042's errata as well).

A new /sys/bus/vme/dma0 device with a new ioctl for making DMA transfers
was introduced in vme_user driver. The logic of the function is similar to
the one found in similar existing drivers.

One question that I had while implementing this feature was whether we
should keep vme_dma_attr objects until vme_dma_list_exec() call. API
doesn't specify this, the existing vme bridge drivers copy all information
from attributes during vme_dma_list_add(). So for simplicity this
implementation frees vme_dma_attr's before vme_dma_list_exec() is done.

A simple test against AVM16 board displays speeds around 45 MiB/s for
A32/D32 reads for both BLT and MBLT (with MBLT being slightly faster).

Dmitry Kalinkin (6):
  Documentation: mention vme_master_mmap() in VME API
  vme: tsi148: fix DMA lists longer that one item
  vme: tsi148: fix first DMA item mapping
  vme: stop DMA transfer on interruption
  staging: vme_user: refactor llseek to switch(){}
  staging: vme_user: provide DMA functionality

 Documentation/vme_api.txt              |   6 ++
 drivers/staging/vme/devices/vme_user.c | 188 +++++++++++++++++++++++++++++++--
 drivers/staging/vme/devices/vme_user.h |  11 ++
 drivers/vme/bridges/vme_ca91cx42.c     |  15 ++-
 drivers/vme/bridges/vme_tsi148.c       |  42 +++++---
 5 files changed, 237 insertions(+), 25 deletions(-)

-- 
1.8.3.1

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