Hi Adam On Wed, 3 Aug 2022 at 12:03, Adam Ford <aford173@xxxxxxxxx> wrote: > > On Wed, Aug 3, 2022 at 1:20 AM Marco Felsch <m.felsch@xxxxxxxxxxxxxx> wrote: > > > > On 22-08-02, Adam Ford wrote: > > > > ... > > > > > > I did some reading about the internal timing generator. It appears > > > > that it's required when video formats use fractional bytes, and it's > > > > preconfigured to run at 720p by default, but registers 28h through 37h > > > > configure it for other video modes. > > > > > > I think there may still be some issues with the DSIM since some of the > > > clock frequencies are set in the device tree. > > > > > > From what I can tell, the pixel rate is calculated based on the > > > > By pixel rate you mean the HDMI pixel rate from the ADV? If so then yes. > > The ADV has an divider which is already configured by the driver but > > meaningless since the driver is lacking of setting the "manual-divider" > > bit within the same register. > > I was thinking about the pixel clock from the DSI to the ADV. I did > see the manual-divider bit was missing. I tried enabling that bit, > but it didn't appear to make much difference. > > > > > burst-clock-frequency and that generates a byte clock. For 891000000, > > > the byte clock is 111375000. > > > > The burst-clock-frequency is the hs-clk and DDR. So the MIPI-DSI clock > > is burst-clock-frequency/2 which is in your case: 891000000/2 = > > 445500000. This clock is than divided by 3 within the ADV and you get > > your 148500000 pixel clock. This divide by 3 is detected automatically > > by the ADV due to the missing bit (see above). > > > > > Modetest timings for 1080p show: > > > > > > index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot > > > #0 1920x1080 60.00 1920 2008 2052 2200 1080 1084 1089 1125 148500 > > > flags: nhsync, nvsync; type: driver > > > > > > > > > When looking at modetest, there is a clock for 1080p which appears to be 148500. > > > 111375000/148500 = 750. > > > > Please see above. > > > > > The rest of the entries in my table do not divide evenly. I don;t > > > know if that explains the lack of display, but it's something to note. > > > It seems to me that instead of fixing the > > > samsung,burst-clock-frequency to 891000000, we should make the desired > > > PLL related to the desired pixel clock so it divides evenly. > > > > Please see above. > > > > > Looking at NXP's kernel, I also noticed that their esc_prescaler is > > > based on the byte clock divided by 20MHz. With some small code > > > changes to get the PLL based on the desired pixel clock instead of > > > hard-coded, I was able to set > > > > > > samsung,burst-clock-frequency = <1500000000>; > > > > This is not correct since the burst-clock-freq. specifies the hs-clock > > for the data lanes (see above). > > But I don't think the clock should be fixed. I think it should vary as > the resolution changes. From what I can tell, NXP's DSI code doesn't > hard code this value, but it does appear to cap it at 1.5G. I did > soom looking into the NXP frequency calculation and it is capable of > adjusting resolutions to some extent and from what I can see the > 891MHz clock is only set when 1080p. At 720p, thier kernel shows the > output frequency at 445.5 MHz. The way the DSIM is currently > configured, it's fixed at 891MHz, so I don't expect the output feeding > the adv7535 to be correct for the different resolutions. > > > > > > > samsung,esc-clock-frequency = <20000000>; > > > > This is correct, we also use a esc-clock of 20MHz. > > > > > With these settings and the above mentioned code changes, 1080p still > > > appears, however when attempting other modes, the display still fails > > > to load. I also noticed that the phy ref clock is set to 27MHz > > > instead of NXP's 12MHz. > > > > That's interesting, I didn't noticed that NXP uses 12 MHz as refclock > > but I don't think that this is the problem. Since we have other > > converter chips using the bridge driver and they work fine. I still > > think that the main problem is within the ADV driver. > > Do the other converter chips work fine at different resolutions? > > > > > > I attempted to play with that setting, but I couldn't get 1080p to > > > work again, so I backed it out. > > > > > > Maybe I am headed in the wrong direction, but I'm going to examine the > > > P/M/S calculation of the timing on NXP's kernel to see how the DSIM in > > > this code compares. > > > > I think the pms values are fine. > > I compared the P/M/S values between this driver and NXP's and they > calculate different values of PMS when running at 1080P. > NXP @ 1080p: > fout = 891000, fin = 12000, m = 297, p = 2, s = 1, best_delta = 0 > > This kernel @ 1080p: > > PLL freq 891000000, (p 3, m 99, s 0) > > at 720P, the NXP Kernel > fout = 445500, fin = 12000, m = 297, p = 2, s = 2, best_delta = 0 > (working) > > at 720P, this kernel: > PLL freq 891000000, (p 3, m 99, s 0) > hs_clk = 891000000, byte_clk = 111375000, esc_clk = 18562500 > (not working) > > > > > > > If someone who understands the interactions between these different > > > components has suggestions, I'm willing to run some experiments. > > > > 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. Mine fairly plainly states: "The DSI receiver input supports DSI video mode operation only, and specifically, only supports nonburst mode with sync pulses". Non-burst mode meaning that the DSI pixel rate MUST be the same as the HDMI pixel rate. Section 6.1.1 "DSI Input Modes" of adv7533_hardware_user_s_guide is even more explicit about the requirement of DSI timing matching The NXP kernel switching down to an hs_clk of 445.5MHz would therefore be correct for 720p operation. 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 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. Dave > adam > > > > Regards, > > Marco
