Hi Thomas, On Fri, Feb 10, 2017 at 09:34:46AM +0000, Thomas Axelsson wrote: > Hi, > > I have a TI AM571x CPU, and I'm trying to add support for multiple MIPI > CSI-2 virtual channels per PHY (port) to the ti-vpe/cal.c driver > (CAMSS/CAL peripheral, ch. 8 in Datasheet [1]). This CPU can have more > contexts (virtual channels) per PHY than what it has DMA handlers. Each > PHY may have up to 8 contexts, and there are 2 PHYs, but there are only 8 > DMA channels in total. It is not required to use DMA to receive data from > the context. Is there a use case for receiving more than eight streams concurrently? I have to admit that this does appear quite exotic if 8 would not suffice. How does the data end up to the system memory if there's no DMA? PIO...? What are the limitations otherwise --- how many PHYs can be used simultaneously? Are the 8 DMAs shared among all? > > Since it will be very useful to specify which contexts will use DMA and which will > not, the proper place to do this seems to be the device tree. > > This becomes rather messy though, since it needs to be specified in the device tree > node pointed to by the remote-endpoint field - yet, it's decided by the capabilities > of the master component (in this case the CAL), so the remote-endpoint is a weird > place to put it. > > I have made an example [2] using the Device Tree example in > Documentation/devicetree/bindings/media/ti-cal.txt (my own comments). > In the ar0330_1 endpoint, I have: > * Put multiple virtual channels in "reg", as in > Documentation/devicetree/bindings/mipi/dsi/mipi-dsi-bus.txt, > * Added "dma-write" for specifying which virtual channels should get written > directly to memory through DMA, > * Added "vip" just to show that a Virtual Channel can go somewhere else than > through DMA write. > * Added "pix-proc" to show that pixel processing might be applied to some of the > Virtual Channels. > > What is your advice on how to properly move forward with adding support like this? > > Thank you in advance. > > Best regards, > Thomas Axelsson > > > [1] http://www.ti.com/lit/gpn/am5716 > > [2] > -------------------------------------------------- > cal: cal@4845b000 { > compatible = "ti,dra72-cal"; > ti,hwmods = "cal"; > > /* snip */ > > ports { > #address-cells = <1>; > #size-cells = <0>; > csi2_0: port@0 { > reg = <0>; /* PHY index, must match port index */ > status = "okay"; /* Enable */ > endpoint { > slave-mode; > remote-endpoint = <&ar0330_1>; > }; > }; > csi2_1: port@1 { > reg = <1>; /* PHY Index */ > }; > }; > }; > > i2c5: i2c@4807c000 { > ar0330@10 { > compatible = "ti,ar0330"; > reg = <0x10>; > port { > #address-cells = <1>; > #size-cells = <0>; > ar0330_1: endpoint { > reg = <0 1 2>; /* Virtual Channels */ > dma-write = <0 2>; /* Virtual Channels that will use > Write DMA */ > vip = <1>; /* Virtual Channel to send on to > Video Input Port */ > pix-proc = <2>; /* Virtual channels to apply pixel > processing on */ > clock-lanes = <1>; /* Clock lane indices */ > data-lanes = <0 2 3 4>; /* Data lane indices */ > remote-endpoint = <&csi2_0>; > }; > }; > }; > }; -- Kind regards, Sakari Ailus e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx
