From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 23BEA16C86A; Wed, 12 Jun 2024 08:21:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718180465; cv=none; b=nA3MbQTIFw+MjWB2/Vpfypv3RaWnTAp3K6+RGVUFZ9D1doRddHr9hsYybHxgPCijMOdvm36gquz2YJ3J8BuAQvyTvbHpRhGW5cicZFJUf2j3foxJzpmn3+DQOgpgdGFuEwjEP3l110PdQ27xpu+qODSw+X0qde+Ojgfx3PGwBWY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718180465; c=relaxed/simple; bh=0aQm+Q4u8OOmf36lomTVoSFtAnohhZsZAjQ39xDxwr0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i47pPtpszLOzjPfvnBNv17PNTq2q08Mph6d/WVCEx16BQJB87lcziiUMRNZPSK/pNri3Q78nr1guOBdlTL+eG9nrr2MipUuh3/rXQqpzRehEcoTHcoQJvTbpKyMkTsI14MoAcE1ip9SooEb7wS22uXdSKEqgaX4qGYxXyPXZxMs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=eIB/WlVT; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="eIB/WlVT" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 63A0C63B; Wed, 12 Jun 2024 10:20:47 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1718180447; bh=0aQm+Q4u8OOmf36lomTVoSFtAnohhZsZAjQ39xDxwr0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eIB/WlVT2qN6aJuVLl/7867V0CY6nqusIX2MJArfp8mc2agxxzFd50Yqk8HQ2qLZU jMpOJ7OjrkVMhc6hGzRgqMMMrj8Rh4F5vIqxLncQBtaQNpFIUtq3M138g4xUTXX0/+ 92ynl9iwhPwH5aTri2hFd/qyyrgrwJAVL6oq5CwQ= Date: Wed, 12 Jun 2024 11:20:40 +0300 From: Laurent Pinchart To: Ricardo Ribalda Cc: Tomasz Figa , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, "hn.chen" , Hans Verkuil , Sergey Senozhatsky Subject: Re: [PATCH v10 4/6] media: uvcvideo: Allow hw clock updates with buffers not full Message-ID: <20240612082040.GD28989@pendragon.ideasonboard.com> References: <20240323-resend-hwtimestamp-v10-0-b08e590d97c7@chromium.org> <20240323-resend-hwtimestamp-v10-4-b08e590d97c7@chromium.org> <4kck7oedsnj6kfiv7ykwsjg35qodg5bdktu5t5w3xtg2xuscto@2yh6kfdqwimc> <20240610114306.GR18479@pendragon.ideasonboard.com> <20240612074342.GA28989@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Jun 12, 2024 at 09:47:26AM +0200, Ricardo Ribalda wrote: > On Wed, 12 Jun 2024 at 09:44, Laurent Pinchart > wrote: > > > > On Wed, Jun 12, 2024 at 12:28:56PM +0900, Tomasz Figa wrote: > > > On Mon, Jun 10, 2024 at 8:43 PM Laurent Pinchart wrote: > > > > On Wed, May 29, 2024 at 05:03:08PM +0900, Tomasz Figa wrote: > > > > > On Sat, Mar 23, 2024 at 10:48:05AM +0000, Ricardo Ribalda wrote: > > > > > > With UVC 1.5 we get as little as one clock sample per frame. Which means > > > > > > that it takes 32 frames to move from the software timestamp to the > > > > > > hardware timestamp method. > > > > > > > > > > > > This results in abrupt changes in the timestamping after 32 frames (~1 > > > > > > second), resulting in noticeable artifacts when used for encoding. > > > > > > > > > > > > With this patch we modify the update algorithm to work with whatever > > > > > > amount of values are available. > > > > > > > > > > > > Tested-by: HungNien Chen > > > > > > Reviewed-by: Sergey Senozhatsky > > > > > > Reviewed-by: Laurent Pinchart > > > > > > Signed-off-by: Ricardo Ribalda > > > > > > --- > > > > > > drivers/media/usb/uvc/uvc_video.c | 16 ++++++++++++++-- > > > > > > 1 file changed, 14 insertions(+), 2 deletions(-) > > > > > > > > > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > > > > > > index d6ca383f643e3..af25b9f1b53fe 100644 > > > > > > --- a/drivers/media/usb/uvc/uvc_video.c > > > > > > +++ b/drivers/media/usb/uvc/uvc_video.c > > > > > > @@ -768,10 +768,10 @@ void uvc_video_clock_update(struct uvc_streaming *stream, > > > > > > > > > > > > spin_lock_irqsave(&clock->lock, flags); > > > > > > > > > > > > - if (clock->count < clock->size) > > > > > > + if (clock->count < 2) > > > > > > goto done; > > > > > > > > > > > > - first = &clock->samples[clock->head]; > > > > > > + first = &clock->samples[(clock->head - clock->count + clock->size) % clock->size]; > > > > > > last = &clock->samples[(clock->head - 1 + clock->size) % clock->size]; > > > > > > > > > > > > /* First step, PTS to SOF conversion. */ > > > > > > @@ -786,6 +786,18 @@ void uvc_video_clock_update(struct uvc_streaming *stream, > > > > > > if (y2 < y1) > > > > > > y2 += 2048 << 16; > > > > > > > > > > > > + /* > > > > > > + * Have at least 1/4 of a second of timestamps before we > > > > > > + * try to do any calculation. Otherwise we do not have enough > > > > > > + * precision. This value was determined by running Android CTS > > > > > > + * on different devices. > > > > > > + * > > > > > > + * dev_sof runs at 1KHz, and we have a fixed point precision of > > > > > > + * 16 bits. > > > > > > + */ > > > > > > + if ((y2 - y1) < ((1000 / 4) << 16)) > > > > > > + goto done; > > > > > > > > > > Not a comment for this patch directly, but... > > > > > > > > > > This kind of makes me wonder if we don't want to have some documentation > > > > > that specifies what the userspace can expect from the timestamps, so > > > > > that this isn't changed randomly in the future breaking what was fixed > > > > > by this patch. > > > > > > > > I think timestamp handling should really be moved to userspace. It will > > > > be easier to handle with floating-point arithmetic there. That would > > > > have been difficult to manage for applications a while ago, but now that > > > > we have libcamera, we could implement it there. This isn't high on my > > > > todo list though. > > > > > > While indeed that would probably be a better way to handle the complex > > > logic if we designed the driver today, we already have userspace that > > > expects the timestamps to be handled correctly in the kernel. I > > > suspect moving it to the userspace would require some core V4L2 > > > changes to define a new timestamp handling mode, where multiple raw > > > hardware timestamps are exposed to the userspace, instead of the high > > > level system monotonic one. > > > > The uvcvideo driver already supports exposing the packet headers to > > userspace through a metadata capture device, so I think we have all the > > components we need. The only missing thing would be the implementation > > in libcamera :-) > > We would still have to duplicate the quirk information in libcamera > and the kernel. Sure, and there will be some level of code duplication. My point is that I believe it can be done in userspace, and while small changes to the clock handling on the kernel side are fine, if we wanted to change the code significantly I think it would be better moved to userspace. I don't have plans to work on this, and I'm not requesting anyone to do so either at this point. -- Regards, Laurent Pinchart