Re: [PATCH v10 6/8] media: i2c: Add TDA1997x HDMI receiver driver

From: Hans Verkuil
Date: Wed Feb 14 2018 - 11:20:59 EST

On 14/02/18 16:46, Tim Harvey wrote:
> On Wed, Feb 14, 2018 at 6:08 AM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
>> Hi Tim,
>>
>> On 12/02/18 23:27, Tim Harvey wrote:
>>> On Fri, Feb 9, 2018 at 12:08 AM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
>>>> Hi Tim,
>>>>
>>>> We're almost there. Two more comments:
>>>>
>>>> On 02/09/2018 07:32 AM, Tim Harvey wrote:
>>>>> +static int
>>>>> +tda1997x_detect_std(struct tda1997x_state *state,
>>>>> + struct v4l2_dv_timings *timings)
>>>>> +{
>>>>> + struct v4l2_subdev *sd = &state->sd;
>>>>> + u32 vper;
>>>>> + u16 hper;
>>>>> + u16 hsper;
>>>>> + int i;
>>>>> +
>>>>> + /*
>>>>> + * Read the FMT registers
>>>>> + * REG_V_PER: Period of a frame (or two fields) in MCLK(27MHz) cycles
>>>>> + * REG_H_PER: Period of a line in MCLK(27MHz) cycles
>>>>> + * REG_HS_WIDTH: Period of horiz sync pulse in MCLK(27MHz) cycles
>>>>> + */
>>>>> + vper = io_read24(sd, REG_V_PER) & MASK_VPER;
>>>>> + hper = io_read16(sd, REG_H_PER) & MASK_HPER;
>>>>> + hsper = io_read16(sd, REG_HS_WIDTH) & MASK_HSWIDTH;
>>>>> + if (!vper || !hper || !hsper)
>>>>> + return -ENOLINK;
>>>>
>>>> See my comment for g_input_status below. This condition looks more like a
>>>> ENOLCK.
>>>>
>>>> Or perhaps it should be:
>>>>
>>>> if (!vper && !hper && !hsper)
>>>> return -ENOLINK;
>>>> if (!vper || !hper || !hsper)
>>>> return -ENOLCK;
>>>>
>>>> I would recommend that you test a bit with no signal and a bad signal (perhaps
>>>> one that uses a pixelclock that is too high for this device?).
>>>
>>> I can't figure out how to produce a signal that can't be locked onto
>>> with what I have available.
>>
>> Are you using a signal generator or just a laptop or something similar as the
>> source?
>>
>> Without a good signal generator it is tricky to test this. A very long HDMI
>> cable would likely do it. But for 1080p60 you probably need 20 meters or
>> more.
>>
>
> I'm using a Marshall V-SG4K-HDI
> (http://www.lcdracks.com/racks/DLW/V-SG4K-HDI-signal-generator.php).
> It does support 'user defined timings' (see
> http://www.lcdracks.com/racks/pdf-pages/instruction_sheets/V-SG4K-HDI_Manual-web.pdf
> Timings Details Menu page) and it looks like the max pixel-clock is
> 300MHz so perhaps I can create a timing that can't be locked onto that
> way.

Yeah, that's what I usually do: try with a signal that's too high/too low.

>
> The TDA19971 datasheet
> (http://tharvey/src/nxp/tda1997x/TDA19971-datasheet-rev3.pdf) says it
> supports:
> - All HDTV formats up to 1920x1080p at 50/60 Hz with support for
> reduced blanking
> - 3D formats including all primary formats up to 1920x1080p at 30 Hz
> Frame Packing and 1920x1080p at 60 Hz Side-by-Side and Top-and-Bottom
> - PC formats up to UXGA (1600x1200p at 60 Hz) and WUXGA (1920x1200p at 60 Hz)

The max pixelclock is probably around 170 MHz. So something above that should
do it.

>
>>>
> <snip>
>>>>
>>>>> +static int
>>>>> +tda1997x_g_input_status(struct v4l2_subdev *sd, u32 *status)
>>>>> +{
>>>>> + struct tda1997x_state *state = to_state(sd);
>>>>> + u32 vper;
>>>>> + u16 hper;
>>>>> + u16 hsper;
>>>>> +
>>>>> + mutex_lock(&state->lock);
>>>>> + v4l2_dbg(1, debug, sd, "inputs:%d/%d\n",
>>>>> + state->input_detect[0], state->input_detect[1]);
>>>>> + if (state->input_detect[0] || state->input_detect[1])
>>>>
>>>> I'm confused. This device has two HDMI inputs?
>>>>
>>>> Does 'detecting input' equate to 'I see a signal and I am locked'?
>>>> I gather from the irq function that sets these values that it is closer
>>>> to 'I see a signal' and that 'I am locked' is something you would test
>>>> by looking at the vper/hper/hsper.
>>>
>>> The TDA19972 and/or TDA19973 has an A and B input but only a single
>>> output. I'm not entirely clear if/how to select between the two and I
>>> don't have proper documentation for the three chips.
>>>
>>> The TDA19971 which I have on my board only has 1 input which is
>>> reported as the 'A' input. I can likely nuke the stuff looking at the
>>> B input and/or put some qualifiers around it but I didn't want to
>>> remove code that was derived from some vendor code that might help
>>> support the other chips in the future. So I would rather like to leave
>>> the 'if A or B' stuff.
>>
>> OK. Can you add a comment somewhere in the driver about this?
>>
>> It sounds like it is similar to what the adv7604 has: several inputs but
>> only one is used for streaming. But the EDID is made available on both inputs.
>>
>
> sure, I will comment about it. I believe that is the way the it works as well.
>
>>>>
>>>>> + *status = 0;
>>>>> + else {
>>>>> + vper = io_read24(sd, REG_V_PER) & MASK_VPER;
>>>>> + hper = io_read16(sd, REG_H_PER) & MASK_HPER;
>>>>> + hsper = io_read16(sd, REG_HS_WIDTH) & MASK_HSWIDTH;
>>>>> + v4l2_dbg(1, debug, sd, "timings:%d/%d/%d\n", vper, hper, hsper);
>>>>> + if (!vper || !hper || !hsper)
>>>>> + *status |= V4L2_IN_ST_NO_SYNC;
>>>>> + else
>>>>> + *status |= V4L2_IN_ST_NO_SIGNAL;
>>>>
>>>> So if we have valid vper, hper and hsper, then there is no signal? That doesn't
>>>> make sense.
>>>>
>>>> I'd expect to see something like this:
>>>>
>>>> if (!input_detect[0] && !input_detect[1])
>>>> // no signal
>>>> else if (!vper || !hper || !vsper)
>>>> // no sync
>>>> else
>>>> // have signal and sync
>>>
>>> sure... reads a bit cleaner. I can't guarantee that any of
>>> vper/hper/vsper will be 0 if a signal can't be locked onto without
>>> proper documentation or ability to generate such a signal. I do know
>>> if I yank the source I get non-zero random values and must rely on the
>>> input_detect logic.
>>
>> Add a comment about this as well. It's good to be clear that this code
>> is partially guesswork and partially based on testing.
>
> ok
>
>>
>>>
>>>>
>>>> I'm not sure about the precise meaning of input_detect, so I might be wrong about
>>>> that bit.
>>>
>>> ya... me either. I'm trying my hardest to get this driver up to shape
>>> but the documentation I have is utter crap and I'm doing some guessing
>>> as well as to what all the registers are and what the meaning of the
>>> very obfuscated vendor code does.
>>>
>>> would you object to detecting timings and displaying via v4l2_dbg when
>>> a resolution change is detected (just not 'using' those timings for
>>> anything?):
>>
>> No, not at all. Also useful is to log the detected timings in the log_status
>> call. It is *very* handy when testing.
>>
>> I.e. if 'v4l2-ctl --log-status' gives you both the configured timings and the
>> detected timings, then that makes it much easier to debug the driver.
>>
>
> ok
>
>>>
>>> @@ -1384,6 +1386,7 @@ static void tda1997x_irq_sus(struct tda1997x_state *state,
>>> u8 *flags)
>>> v4l_err(state->client, "BAD SUS STATUS\n");
>>> return;
>>> }
>>> + if (debug)
>>> + tda1997x_detect_std(state, NULL);
>>> /* notify user of change in resolution */
>>> v4l2_subdev_notify_event(&state->sd, &tda1997x_ev_fmt);
>>> }
>>>
>>> @@ -1140,16 +1140,18 @@ tda1997x_detect_std(struct tda1997x_state *state,
>>> /* hsmatch matches the hswidth */
>>> hsmatch = ((hsper <= hsmax) && (hsper >= hsmin)) ? 1 : 0;
>>> if (hmatch && vmatch && hsmatch) {
>>> - *timings = v4l2_dv_timings_presets[i];
>>> v4l2_print_dv_timings(sd->name, "Detected format: ",
>>> - timings, false);
>>> + &v4l2_dv_timings_presets[i],
>>> + false);
>>> + if (timings)
>>> + *timings = v4l2_dv_timings_presets[i];
>>> return 0;
>>> }
>>> }
>>>
>>> It seems to make sense to me to be seeing a kernel message when
>>> timings change and what they change to without having to query :)
>>
>> Right.
>>
>> I'll wait for v11 and I'll make a pull request for it.
>>
>
> hopefully I'll get to v11 later today.
>
> Thanks!
>
> Tim
>

Regards,

Hans