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 A87181A5B9E; Thu, 25 Sep 2025 12:44:18 +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=1758804260; cv=none; b=j4Uu0iwOhko0iPKz0DnAx7YOZUUzZam1csfX5fpoq5EQ8NfeBYCYW2kzpeh7p6HtI4ejVL1SREivqGtODd4rAOxQDjAryf3CKmHLxDGPh8if/FmSlw4l7KZ/cb/t0tdUWZSbfRTzwA202u1YgYMWk2GRtyewemnbw36JCxe59zc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758804260; c=relaxed/simple; bh=QmGmn3+dtNbLHQC1nbIC/IJWmcaevKdkI0kLT4TRyV8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Qn1Iy9wKb0QJyus6lyXTJRKVB3/v+1r1juN+Ue0ZaG+IVypGkF3wpfahWlhqhwhbWkQX6V69cSIACjwcHQRH2HM5tXfLoB+xCF4qOkXJ6fHijVPl5F6+R8vvVYOgHI3vmqpihDiQcdeQzFtpK6SwXmTH/v8nE83pukPCkRo2pwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (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=O89KvNSq; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (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="O89KvNSq" Received: from [192.168.88.20] (91-158-153-178.elisa-laajakaista.fi [91.158.153.178]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id EFBAD1AC5; Thu, 25 Sep 2025 14:42:50 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1758804172; bh=QmGmn3+dtNbLHQC1nbIC/IJWmcaevKdkI0kLT4TRyV8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=O89KvNSq+0Yw7Yuvl9ChFeh1WUbCT07bkSYIH20SKFYAeUOOVWr5P7mjqg32jLmNh JxCWGws5v89IDD9toYuWxxQmsc6GKCjNfw+4q5BPpiXGsntklFveYvabFnk2Fccsuh wIXQBW+/Psq+d6OZPbTX5GgXrv+tCzf27ejc3iRU= Message-ID: <364c3b35-81a0-4e93-ad3b-a0fff3a29365@ideasonboard.com> Date: Thu, 25 Sep 2025 15:44:13 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 10/16] media: cadence: csi2rx: add multistream support To: Rishikesh Donadkar , jai.luthra@linux.dev, laurent.pinchart@ideasonboard.com, mripard@kernel.org Cc: y-abhilashchandra@ti.com, devarsht@ti.com, s-jain1@ti.com, vigneshr@ti.com, mchehab@kernel.org, robh@kernel.org, krzk+dt@kernel.org, p.zabel@pengutronix.de, conor+dt@kernel.org, sakari.ailus@linux.intel.com, hverkuil-cisco@xs4all.nl, jai.luthra@ideasonboard.com, changhuang.liang@starfivetech.com, jack.zhu@starfivetech.com, sjoerd@collabora.com, hverkuil+cisco@kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org References: <20250911102832.1583440-1-r-donadkar@ti.com> <20250911102832.1583440-11-r-donadkar@ti.com> Content-Language: en-US From: Tomi Valkeinen Autocrypt: addr=tomi.valkeinen@ideasonboard.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, On 11/09/2025 13:28, Rishikesh Donadkar wrote: > From: Jai Luthra > > Cadence CSI-2 bridge IP supports capturing multiple virtual "streams" > of data over the same physical interface using MIPI Virtual Channels. > > While the hardware IP supports usecases where streams coming in the sink > pad can be broadcasted to multiple source pads, the driver will need > significant re-architecture to make that possible. The two users of this > IP in mainline linux are TI Shim and StarFive JH7110 CAMSS, and both > have only integrated the first source pad i.e stream0 of this IP. So for > now keep it simple and only allow 1-to-1 mapping of streams from sink to > source, without any broadcasting. > > The enable_streams() API in v4l2 supports passing a bitmask to enable > each pad/stream combination individually on any media subdev. Use this > API instead of s_stream() API. > > Implement the enable_stream and disable_stream hooks in place of the > stream-unaware s_stream hook. > > Implement a fallback s_stream hook that internally calls enable_stream > on each source pad, for consumer drivers that don't use multi-stream > APIs to still work. The helper function v4l2_subdev_s_stream_helper() > form the v4l2 framework is not used here as it is meant only for the > subedvs that have a single source pad and this hardware IP supports > having multiple source pads. > +static int csi2rx_enable_streams(struct v4l2_subdev *subdev, > + struct v4l2_subdev_state *state, u32 pad, > + u64 streams_mask) > +{ > + struct csi2rx_priv *csi2rx = v4l2_subdev_to_csi2rx(subdev); > + u64 sink_streams; > + int ret; > + > + sink_streams = v4l2_subdev_state_xlate_streams(state, pad, > + CSI2RX_PAD_SINK, > + &streams_mask); > + > + guard(mutex)(&csi2rx->lock); This looks a bit odd too. With enable/disable_streams, the state is already locked. What is the mutex protecting? j721e-csi2rx also has mutexes, and it's very unclear what they protect. This should be described in the code. I think in csi2rx the whole mutex can be just dropped. j721e-csi2rx is a bit more complex, but there also I would consider if and when the state lock protects the relevant parts already, and when another lock is needed, what is the sequence to lock/unlock (e.g. always csi->mutex first, then csi->subdev state lock), and make sure the code follows that. Tomi