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[139.181.7.34]) by smtp.gmail.com with ESMTPSA id i192sm31968476wmg.7.2019.01.14.17.03.37 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Jan 2019 17:03:38 -0800 (PST) Subject: Re: [RFC PATCH v2] media: rcar-vin: Allow independent VIN link enablement From: Steve Longerbeam To: =?UTF-8?Q?Niklas_S=c3=b6derlund?= Cc: linux-media@vger.kernel.org, Mauro Carvalho Chehab , "open list:MEDIA DRIVERS FOR RENESAS - VIN" , open list References: <20190106212018.16519-1-slongerbeam@gmail.com> <20190109224039.GD24252@bigcity.dyn.berto.se> Message-ID: <8ebc5152-1566-b5f5-1fef-2937b4f2e290@gmail.com> Date: Mon, 14 Jan 2019 17:03:35 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-renesas-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org On 1/9/19 5:19 PM, Steve Longerbeam wrote: > > > On 1/9/19 2:40 PM, Niklas Söderlund wrote: >> Hi Steve, >> >> Thanks for your patch, I think it looks good. > > Thanks for the Ack! I'm not real familiar with the RFC patch process. > Should this be submitted again with RFC stripped from the subject line? I've been told there isn't really a process for RFC patch submission. I will re-submit and strip off the RFC and add your Reviewed-by. Steve > > >> On 2019-01-06 13:20:18 -0800, Steve Longerbeam wrote: >>> There is a block of code in rvin_group_link_notify() that loops through >>> all entities in the media graph, and prevents enabling a link to a VIN >>> node if any entity is in use. This prevents enabling a VIN link even if >>> there is an in-use entity somewhere in the graph that is independent of >>> the link's pipeline. >>> >>> For example, the code will prevent enabling a link from the first >>> rcar-csi2 receiver to a VIN node even if there is an enabled link >>> somewhere far upstream on the second independent rcar-csi2 receiver >>> pipeline. >>> >>> If this code is meant to prevent modifying a link if any entity in the >>> graph is actively involved in streaming (because modifying the CHSEL >>> register fields can disrupt any/all running streams), then the entities >>> stream counts should be checked rather than the use counts. >>> >>> (There is already such a check in __media_entity_setup_link() that >>> verifies >>> the stream_count of the link's source and sink entities are both zero, >>> but that is insufficient, since there should be no running streams in >>> the entire graph). >>> >>> Modify the media_device_for_each_entity() loop to check the entity >>> stream_count instead of the use_count, and elaborate on the comment. >>> VIN node links can now be enabled even if there are other independent >>> in-use entities that are not streaming. >>> >>> Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3") >>> >>> Signed-off-by: Steve Longerbeam >> Reviewed-by: Niklas Söderlund >> >>> --- >>> Changes in v2: >>> - bring back the media_device_for_each_entity() loop but check the >>>    stream_count not the use_count. >>> --- >>>   drivers/media/platform/rcar-vin/rcar-core.c | 8 ++++++-- >>>   1 file changed, 6 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c >>> b/drivers/media/platform/rcar-vin/rcar-core.c >>> index f0719ce24b97..6dd6b11c1b2b 100644 >>> --- a/drivers/media/platform/rcar-vin/rcar-core.c >>> +++ b/drivers/media/platform/rcar-vin/rcar-core.c >>> @@ -131,9 +131,13 @@ static int rvin_group_link_notify(struct >>> media_link *link, u32 flags, >>> !is_media_entity_v4l2_video_device(link->sink->entity)) >>>           return 0; >>>   -    /* If any entity is in use don't allow link changes. */ >>> +    /* >>> +     * Don't allow link changes if any entity in the graph is >>> +     * streaming, because modifying the CHSEL register fields >>> +     * can disrupt running streams. >>> +     */ >>>       media_device_for_each_entity(entity, &group->mdev) >>> -        if (entity->use_count) >>> +        if (entity->stream_count) >>>               return -EBUSY; >>>         mutex_lock(&group->lock); >>> -- >>> 2.17.1 >>> >