On Thu, Aug 4, 2022 at 9:52 AM Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx> wrote: > > On Thu, 4 Aug 2022 at 13:51, Marco Felsch <m.felsch@xxxxxxxxxxxxxx> wrote: > > > > Hi Dave, > > > > On 22-08-04, Dave Stevenson wrote: > > > Hi Marco > > > > > > On Thu, 4 Aug 2022 at 10:38, Marco Felsch <m.felsch@xxxxxxxxxxxxxx> wrote: > > > > > > > > Hi Dave, Adam, > > > > > > > > On 22-08-03, Dave Stevenson wrote: > > > > > Hi Adam > > > > > > > > > > On Wed, 3 Aug 2022 at 12:03, Adam Ford <aford173@xxxxxxxxx> wrote: > > > > > > > > ... > > > > > > > > > > > Did managed to get access to the ADV7535 programming guide? This is the > > > > > > > black box here. Let me check if I can provide you a link with our repo > > > > > > > so you can test our current DSIM state if you want. > > > > > > > > > > > > I do have access to the programming guide, but it's under NDA, but > > > > > > I'll try to answer questions if I can. > > > > > > > > > > Not meaning to butt in, but I have datasheets for ADV7533 and 7535 > > > > > from previously looking at these chips. > > > > > > > > Thanks for stepping into :) > > > > > > > > > Mine fairly plainly states: > > > > > "The DSI receiver input supports DSI video mode operation only, and > > > > > specifically, only supports nonburst mode with sync pulses". > > > > > > > > I've read this also, and we are working in nonburst mode with sync > > > > pulses. I have no access to an MIPI-DSI analyzer therefore I can't > > > > verify it. > > > > > > > > > Non-burst mode meaning that the DSI pixel rate MUST be the same as the > > > > > HDMI pixel rate. > > > > > > > > On DSI side you don't have a pixel-clock instead there is bit-clock. > > > > > > You have an effective pixel clock, with a fixed conversion for the > > > configuration. > > > > > > DSI bit-clock * number of lanes / bits_per_pixel = pixel rate. > > > 891Mbit/s * 4 lanes / 24bpp = 148.5 Mpixels/s > > > > Okay, I just checked the bandwidth which must equal. > > > > > As noted elsewhere, the DSI is DDR, so the clock lane itself is only > > > running at 891 / 2 = 445.5MHz. > > > > > > > > Section 6.1.1 "DSI Input Modes" of adv7533_hardware_user_s_guide is > > > > > even more explicit about the requirement of DSI timing matching > > > > > > > > Is it possible to share the key points of the requirements? > > > > > > "Specifically the ADV7533 supports the Non-Burst Mode with syncs. This > > > mode requires real time data generation as a pulse packet received > > > becomes a pulse generated. Therefore this mode requires a continuous > > > stream of data with correct video timing to avoid any visual > > > artifacts." > > > > > > LP mode is supported on data lanes. Clock lane must remain in HS mode. > > > > > > "... the goal is to accurately convey DPI-type timing over DSI. This > > > includes matching DPI pixel-transmission rates, and widths of timing > > > events." > > > > Thanks for sharing. > > > > > > > The NXP kernel switching down to an hs_clk of 445.5MHz would therefore > > > > > be correct for 720p operation. > > > > > > > > It should be absolute no difference if you work on 891MHz with 2 lanes > > > > or on 445.5 MHz with 4 lanes. What must be ensured is that you need the > > > > minimum required bandwidth which is roughly: 1280*720*24*60 = 1.327 > > > > GBps. > > > > > > Has someone changed the number of lanes in use? I'd missed that if so, > > > but I'll agree that 891MHz over 2 lanes should work for 720p60. > > > > The ADV driver is changing it autom. but this logic is somehow odd and > > there was already a approach to stop the driver doing this. > > I'd missed that bit in the driver where it appears to drop to 3 lanes > for pixel clock < 80000 via a mipi_dsi_detach and _attach. Quirky, but > probably the only way it can be achieved in the current framework. > > > To sync up: we have two problems: > > 1) The 720P mode with static DSI host configuration isn't working > > without hacks. > > 2) The DSI link frequency should changed as soon as required > > automatically. So we can provide all modes. > > > > I would concentrate on problem 1 first before moving on to the 2nd. > > If you change your link frequency, it may be worth trying a lower > resolution again such as 720x480 @ 60fps on 2 lanes. (720480@60 on 4 > lanes is again listed as mandatory for using the timing generator). > > > > I have just noted that 720p59.94 at 24bpp on 4 lanes is listed as one > > > of the modes that is mandatory to use the timing generator (reg 0x27 > > > bit 7 = 1). On 2 lanes it is not required. > > > I don't know why it's referencing the 1000/1001 pixel clock rates and > > > not the base one, as it's only a base clock change with the same > > > timing (74.176MHz clock instead of 74.25MHz). > > > > Interesting! I would like to know how the HDMI block gets fetched by the > > DSI block and how the timing-generator can influence this in good/bad > > way. So that we know what DSI settings (freq, lanes) are sufficient. > > > > > > > If you do program the manual DSI divider register to allow a DSI pixel > > > > > rate of 148.5MHz vs HDMI pixel rate of 74.25MHz, you'd be relying on > > > > > > > > There is no such DSI pixel rate to be precise, we only have a DSI bit > > > > clock/rate. > > > > > > > > > the ADV753x having at least a half-line FIFO between DSI rx and HDMI > > > > > tx to compensate for the differing data rates. I see no reference to > > > > > such, and I'd be surprised if it was more than a half dozen pixels to > > > > > compensate for the jitter in the cases where the internal timing > > > > > generator is mandatory due to fractional bytes. > > > > > > > > This is interesting and would proofs our assumption that the device > > > > don't have a FIFO :) > > > > > > > > Our assumptions (we don't have the datasheet/programming manual): > > > > - HDMI part is fetching 3 bytes per HDMI pixclk > > > > - Ratio between dsi-clk and hdmi-pixelclk must be 3 so the DSI and > > > > HDMI are in sync. So from bandwidth pov there are no differences > > > > between: > > > > - HDMI: 74.25 MHz * 24 Bit = 1782.0 MBit/s > > > > - DSI: 891 MHz * 2 lanes = 1782.0 MBit/s (dsi-clock: 445.5 ) > > > > - DSI: 445.5 MHz * 4 lanes = 1782.0 MBit/s (dsi-clock: 222.75) > > > > > > > > But the ratio is different and therefore the faster clocking option > > > > let something 'overflow'. > > > > > > I'll agree that all looks consistent. > > > > > > > Anyway, but all this means that Adam should configure the > > > > burst-clock-rate to 445.5 and set the lanes to 4. But this doesn't work > > > > either and now we are back on my initial statement -> the driver needs > > > > some attention. > > > > > > Things always need attention :-) > > > > ^^ > > > > > I suspect that it's the use of the timing generator that is the issue. > > > The programming guide does recommend using it for all modes, so that > > > would be a sensible first step. > > > > But I tested it without the timing-generator too. Can you or Adam verify > > the timing-generator diable logic? > > Sorry, running without the use of the timing generator is the issue. > It is mandatory in some modes, but supported in all modes. Always > using it should therefore avoid not using it in one of the mandatory > modes (the list looks a little arbitrary). > > > > I will say that we had a number of issues getting this chip to do > > > anything, and it generally seemed happier on 2 or 3 lanes instead of > > > 4. Suffice to say that we abandoned trying to use it, despite some > > > assistance from ADI. > > > > Even more interessting, what is your alternative to this chip? > > BCM2711 which supported dual HDMI natively. > Our investigation of ADV7535 was when trying to build what became > Pi400 using BCM2710/BCM2837 (only has a single HDMI output). Whilst I > do have the prototype, the ADV was wired up weirdly with I2C so I > never really got it running with Linux. I think I have convinced myself that the DSIM is working good enough to match that of the NXP. I've gone through and made a list of the register differences between a working display using NXP's kernel and the non-working display. I've identified a small handful of registers on both the CEC bank of registers and main set of registers. I noticed that the working NXP version doesn't rescale the number of lanes based on the clock rate, and it stays fixed at 4 lanes. That might actually explain some of the issues I am seeing on their kernel still not syncing at low resolutions. I'm going to try to go through the code and identify other differences and see if I can hack this version of the ADv7535 driver to get it into a similar working state as the NXP one (not that theirs is the best). With a couple of the hacks, I can get my screen to sync, but it just displays blue, so I think I am making some progress. I should have a few more hours tomorrow to work on this. It's a side-project for me, but I have time over the weekend too. adam > > Dave
