From patchwork Sat Aug 3 22:09:34 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Keith Pyle X-Patchwork-Id: 57870 X-Patchwork-Delegate: hverkuil@xs4all.nl Received: from vger.kernel.org ([209.132.180.67]) by www.linuxtv.org with esmtp (Exim 4.84_2) (envelope-from ) id 1hu2Dd-0004IE-TN; Sat, 03 Aug 2019 22:09:42 +0000 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729188AbfHCWJj (ORCPT + 1 other); Sat, 3 Aug 2019 18:09:39 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:56400 "EHLO cdptpa-cmomta02.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729178AbfHCWJj (ORCPT ); Sat, 3 Aug 2019 18:09:39 -0400 Received: from [192.168.2.97] ([72.182.16.184]) by cmsmtp with ESMTP id u2DWhQMDKzc56u2DZhlLia; Sat, 03 Aug 2019 22:09:37 +0000 To: Linux Media Mailing List From: Keith Pyle Subject: [PATCH 1/2]: media: hdpvr: Add adaptive sleeping in hdpvr_start_streaming Message-ID: Date: Sat, 3 Aug 2019 17:09:34 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.0 MIME-Version: 1.0 Content-Language: en-US X-CMAE-Envelope: MS4wfLEPw8ioJY3sfYEmvFugf1jy2uoLodunuSgTtynhPwIaM899pCZlSv3AfHYvkCPjiIYD7332+TdDpT1VYdDwb/GoB5XA8Za3lSJB4GADGmZTkjNq+kLh JqBWWImLXsUkKCJVIBo46wGtJysZco0eNuebOhLTdStkUxZ9jUNWiErc20iXFTg3ZkDUwfhCsH1Fnw== Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org The hdpvr firmware reacts poorly to a fast close/open sequence. Delaying a few seconds between the close and next open produces generally reliable results. Rather than requiring user programs to implement this delay and coordinate among themselves when the device is handed from one program to another, add kernel support for delaying the attempt to start streaming if the device only recently stopped streaming. A delay of 4 seconds seems to be sufficient, but some administrators may wish to push their luck by trying shorter delays. To allow administrators to change the delay, add a new parameter to the hdpvr module: `hdpvr_close_to_open_ms_delay`, which specifies the delay in milliseconds between a close and subsequent start-streaming. If the user application has already delayed by at least that long for its own reasons, this feature will add no further delay. Signed-off-by: Keith Pyle Tested-by: Keith Pyle --- Changes since v2: - Rewrapped comments again, per request from Hans. - Per advice from checkpatch.pl --strict (suggested by Hans), added spacing around `|` for mode permissions. This satisfies checkpatch, but reduces consistency in hdpvr-core.c, which had preexisting uses that violate checkpatch --strict. - Changed indentation of declaration of jiffies_next_start_streaming to line up when viewed with tabstop=8. Changes since v1: - Rewrapped output at 80 columns, per request from Hans. Literal strings still exceed 80 columns where necessary to keep an entire string together, since this makes it easier for grep to find the file and line that generates a given message. - Reviewed Hans request to use `jiffies` instead of `get_jiffies_64()`. Per the documentation, raw `jiffies` appears to be inappropriate on 32-bit systems, so the patch continues to use `get_jiffies_64()`. On 64-bit systems, `get_jiffies_64()` becomes a direct read of `jiffies`. Further, both uses of `get_jiffies_64()` are on relatively cold paths (one just before starting streaming, the other just before a 10ms hardcoded sleep), so the performance impact even on the 32-bit path should be trivial relative to the time required for the surrounding code. --- drivers/media/usb/hdpvr/hdpvr-core.c | 4 ++++ drivers/media/usb/hdpvr/hdpvr-video.c | 22 ++++++++++++++++++++++ drivers/media/usb/hdpvr/hdpvr.h | 5 +++++ 3 files changed, 31 insertions(+) diff --git a/drivers/media/usb/hdpvr/hdpvr-core.c b/drivers/media/usb/hdpvr/hdpvr-core.c index 23d3d0754308..a3d2f632fe38 100644 --- a/drivers/media/usb/hdpvr/hdpvr-core.c +++ b/drivers/media/usb/hdpvr/hdpvr-core.c @@ -39,6 +39,10 @@ int hdpvr_debug; module_param(hdpvr_debug, int, S_IRUGO|S_IWUSR); MODULE_PARM_DESC(hdpvr_debug, "enable debugging output"); +uint hdpvr_close_to_open_ms_delay = 4000; +module_param(hdpvr_close_to_open_ms_delay, uint, S_IRUGO | S_IWUSR); +MODULE_PARM_DESC(hdpvr_close_to_open_ms_delay, "delay restarting streaming by the specified number of milliseconds"); + static uint default_video_input = HDPVR_VIDEO_INPUTS; module_param(default_video_input, uint, S_IRUGO|S_IWUSR); MODULE_PARM_DESC(default_video_input, "default video input: 0=Component / 1=S-Video / 2=Composite"); diff --git a/drivers/media/usb/hdpvr/hdpvr-video.c b/drivers/media/usb/hdpvr/hdpvr-video.c index 3d199d5d6738..7e5897dd8dff 100644 --- a/drivers/media/usb/hdpvr/hdpvr-video.c +++ b/drivers/media/usb/hdpvr/hdpvr-video.c @@ -278,6 +278,8 @@ static int hdpvr_start_streaming(struct hdpvr_device *dev) { int ret; struct hdpvr_video_info vidinf; + u64 now_jiffies, delta_jiffies; + uint msec_to_sleep; if (dev->status == STATUS_STREAMING) return 0; @@ -298,6 +300,22 @@ static int hdpvr_start_streaming(struct hdpvr_device *dev) v4l2_dbg(MSG_BUFFER, hdpvr_debug, &dev->v4l2_dev, "video signal: %dx%d@%dhz\n", vidinf.width, vidinf.height, vidinf.fps); + now_jiffies = get_jiffies_64(); + /* inline time_after64 since the result of the subtraction is needed for + * the sleep + */ + delta_jiffies = dev->jiffies_next_start_streaming - now_jiffies; + if ((__s64)delta_jiffies > 0) { + /* device firmware may not be ready yet */ + msec_to_sleep = jiffies_to_msecs(delta_jiffies); + v4l2_dbg(MSG_INFO, hdpvr_debug, &dev->v4l2_dev, + "firmware may not be ready, sleeping for %u ms\n", + msec_to_sleep); + msleep(msec_to_sleep); + } else { + v4l2_dbg(MSG_INFO, hdpvr_debug, &dev->v4l2_dev, + "firmware assumed to be ready, not sleeping\n"); + } /* start streaming 2 request */ hdpvr_usb_lock(dev, HDPVR_USB_CTRL); @@ -332,6 +350,7 @@ static int hdpvr_stop_streaming(struct hdpvr_device *dev) int actual_length; uint c = 0; u8 *buf; + u64 now_jiffies; if (dev->status == STATUS_IDLE) return 0; @@ -368,6 +387,9 @@ static int hdpvr_stop_streaming(struct hdpvr_device *dev) kfree(buf); v4l2_dbg(MSG_BUFFER, hdpvr_debug, &dev->v4l2_dev, "used %d urbs to empty device buffers\n", c-1); + now_jiffies = get_jiffies_64(); + dev->jiffies_next_start_streaming = now_jiffies + + msecs_to_jiffies(hdpvr_close_to_open_ms_delay); msleep(10); dev->status = STATUS_IDLE; diff --git a/drivers/media/usb/hdpvr/hdpvr.h b/drivers/media/usb/hdpvr/hdpvr.h index 7b3d166da1dd..32498b7120aa 100644 --- a/drivers/media/usb/hdpvr/hdpvr.h +++ b/drivers/media/usb/hdpvr/hdpvr.h @@ -43,6 +43,7 @@ /* #define HDPVR_DEBUG */ extern int hdpvr_debug; +extern uint hdpvr_close_to_open_ms_delay; #define MSG_INFO 1 #define MSG_BUFFER 2 @@ -95,6 +96,10 @@ struct hdpvr_device { struct v4l2_dv_timings cur_dv_timings; uint flags; + /* earliest jiffies at which the device firmware will be ready to start + * streaming + */ + u64 jiffies_next_start_streaming; /* synchronize I/O */ struct mutex io_mutex;