Re: [PATCH 04/22] [media] v4l2-subdev.h: add prepare_stream op
On Fri, Oct 14, 2016 at 05:48:43PM +0200, Philipp Zabel wrote: > Am Samstag, den 08.10.2016, 02:16 +0300 schrieb Sakari Ailus: > > Hi Philipp, > > > > On Fri, Oct 07, 2016 at 06:00:49PM +0200, Philipp Zabel wrote: > > > In some cases, for example MIPI CSI-2 input on i.MX6, the sending and > > > receiving subdevice need to be prepared in lock-step before the actual > > > streaming can start. In the i.MX6 MIPI CSI-2 case, the sender needs to > > > put its MIPI CSI-2 transmitter lanes into stop state, and the receiver > > > needs to configure its D-PHY and detect the stop state on all active > > > lanes. Only then the sender can be enabled to stream data and the > > > receiver can lock its PLL to the clock lane. > > > > Is there a need to explicitly control this? Shouldn't this already be the > > case when the transmitting device is powered on and is not streaming? > > Even if the transmitter is expected to keep the lanes in this stop state > all the time while the subdevice is powered but not streaming, I still > have to wait for stop state detection before enabling the transmitter, > and only then enable the reciever. > I'll remove the prepare_streaming callback in the next version and > instead let the subdevices propagate s_stream upstream instead in the > next version. Ack. As discussed, I'll provide a patch to document this behaviour on CSI-2. I believe the current drivers implicitly implement it but you're the first one to ask the question. :-) -- Sakari Ailus e-mail: sakari.ai...@iki.fi XMPP: sai...@retiisi.org.uk -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 04/22] [media] v4l2-subdev.h: add prepare_stream op
Am Samstag, den 08.10.2016, 02:16 +0300 schrieb Sakari Ailus: > Hi Philipp, > > On Fri, Oct 07, 2016 at 06:00:49PM +0200, Philipp Zabel wrote: > > In some cases, for example MIPI CSI-2 input on i.MX6, the sending and > > receiving subdevice need to be prepared in lock-step before the actual > > streaming can start. In the i.MX6 MIPI CSI-2 case, the sender needs to > > put its MIPI CSI-2 transmitter lanes into stop state, and the receiver > > needs to configure its D-PHY and detect the stop state on all active > > lanes. Only then the sender can be enabled to stream data and the > > receiver can lock its PLL to the clock lane. > > Is there a need to explicitly control this? Shouldn't this already be the > case when the transmitting device is powered on and is not streaming? Even if the transmitter is expected to keep the lanes in this stop state all the time while the subdevice is powered but not streaming, I still have to wait for stop state detection before enabling the transmitter, and only then enable the reciever. I'll remove the prepare_streaming callback in the next version and instead let the subdevices propagate s_stream upstream instead in the next version. regards Philipp -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 04/22] [media] v4l2-subdev.h: add prepare_stream op
Hi Philipp, On Fri, Oct 07, 2016 at 06:00:49PM +0200, Philipp Zabel wrote: > In some cases, for example MIPI CSI-2 input on i.MX6, the sending and > receiving subdevice need to be prepared in lock-step before the actual > streaming can start. In the i.MX6 MIPI CSI-2 case, the sender needs to > put its MIPI CSI-2 transmitter lanes into stop state, and the receiver > needs to configure its D-PHY and detect the stop state on all active > lanes. Only then the sender can be enabled to stream data and the > receiver can lock its PLL to the clock lane. Is there a need to explicitly control this? Shouldn't this already be the case when the transmitting device is powered on and is not streaming? -- Kind regards, Sakari Ailus e-mail: sakari.ai...@iki.fi XMPP: sai...@retiisi.org.uk -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
