linux-kernel - [PATCH v5 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

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Date:   Tue, 21 Aug 2018 20:06:27 +0300
From:   "Matwey V. Kornilov" <matwey@....msu.ru>
To:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     matwey.kornilov@...il.com,
        "Matwey V. Kornilov" <matwey@....msu.ru>, tfiga@...omium.org,
        laurent.pinchart@...asonboard.com, stern@...land.harvard.edu,
        ezequiel@...labora.com, hdegoede@...hat.com, hverkuil@...all.nl,
        mchehab@...nel.org, rostedt@...dmis.org, mingo@...hat.com,
        isely@...ox.com, bhumirks@...il.com, colin.king@...onical.com,
        kieran.bingham@...asonboard.com, keiichiw@...omium.org
Subject: [PATCH v5 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

DMA cocherency slows the transfer down on systems without hardware coherent
DMA. In order to demontrate this we introduce performance measurement
facilities in patch 1 and fix the performance issue in patch 2 in order to
obtain 4 times speedup.

Changes since v4:
 * fix fields order in trace events 
 * minor style fixes

Changes since v3:
 * fix scripts/checkpatch.pl errors
 * use __string to store name in trace events

Changes since v2:
 * use dma_sync_single_for_cpu() to achive better performance
 * remeasured performance

Changes since v1:
 * trace_pwc_handler_exit() call moved to proper place
 * detailed description added for commit 1
 * additional output added to trace to track separate frames

Matwey V. Kornilov (2):
  media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler()
  media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

 drivers/media/usb/pwc/pwc-if.c | 64 ++++++++++++++++++++++++++++++++---------
 include/trace/events/pwc.h     | 65 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 116 insertions(+), 13 deletions(-)
 create mode 100644 include/trace/events/pwc.h

-- 
2.16.4