[alsa-devel] ASoC: Intel: sst: Missing IRQ at index 5 on BYT-T device

[Pierre-Louis Bossart]

On 12/19/18 7:07 AM, Stephan Gerhold wrote:
> On Mon, Dec 17, 2018 at 08:13:36PM -0600, Pierre-Louis Bossart wrote:
>>
>>>>>> The quirks to get sound working with bytcr-rt5640 on that device are:
>>>>>> BYT_RT5640_SSP0_AIF1 | BYT_RT5640_IN1_MAP | BYT_RT5640_MCLK_EN
>>>>>>
>>>>>> I guess this means that SSP0 is being used?
>>>>> Yes indeed, and that makes me think we should force this device to look like
>>>>> Baytrail-CR.
>>>>>
>>>>> You can do this with a DMI-based quirk (preferably in is_byt_cr directly so
>>>>> that I can reuse the code when I move it to a helper at some point).
>>>> Okay - thanks! One last question:
>>>> I was looking at the ACPI DSDT tables of some similar devices and have
>>>> found two others that look the same (only one IRQ listed). In this case,
>>>> the BYT-T acpi_ipc_irq_index = 5 will never work, and we will definitely
>>>> have a better chances with trying Baytrail-CR.
>>>>
>>>> One of them actually had a similar patch proposed at [1] (although they
>>>> did it in a weird way and also need an extra machine driver).
>>>>
>>>> We could also detect this situation in a generic way with something like
>>>>
>>>>     if (platform_irq_count(pdev) == 1) {
>>>>     	*bytcr = true;
>>>> 	return 0;
>>>>     }
>>>>
>>>> ... instead of a DMI quirk. What do you think?
>>>>
>>> To avoid confusion: The existing PMIC-type based is_byt_cr() detection
>>> would be used in all other cases (i.e. if irq_count != 1), so it won't
>>> make any difference for the devices that are already working fine.
>>> (Most BYT-CR devices seem to have 5 IRQs listed)
>>>
>>> So it's more like
>>>
>>>     if (platform_irq_count(pdev) == 1) {
>>>     	*bytcr = true;
>>>     } else {
>>>     	// pmic-type based detection...
>>>     }
>>>
>>> with platform_irq_count == 1 as condition for the "quirk".
>>
>> The solution seems appealing but
>>
>> 1) does it really work? I am not sure an index=5 means there are 5
>> interrupts.
> 
> Yes, I believe that it means that there need to be (at least) 5
> interrupts.
> 
> I have checked the source code of platform_get_irq.
> When you do platform_get_irq(pdev, /* index = */ 5) (as done for BYT-T)
> it first calls
> 
>      platform_get_resource(/* type = */ IORESOURCE_IRQ, /* num = */ 5)
> 
> to lookup the resource. That method is really simple and looks like
> 
> 	for (i = 0; i < dev->num_resources; i++) {
> 		struct resource *r = &dev->resource[i];
> 
> 		if (type == resource_type(r) && num-- == 0)
> 			return r;
> 	}
> 
> So when you request an IRQ at index=5, it loops through all resources,
> skips the first 5 IRQs and returns the 6th one (on my device, it
> returns NULL because there are not enough IRQs listed).
> 
> There is a bit more magic in platform_irq_count (it looks up all IRQs
> and does not count invalid ones), so to be absolutely safe we could
> just check platform_get_resource(IRQ, 5) == NULL early.
> If it returns NULL, then platform_get_irq(pdev, 5) will also return
> -ENXIO, so treating the device as BYT-T is guaranteed to fail.
> In this case, we have better chances when we assume BYT-CR.
> 
> Example patch: (I have added it in probe instead of is_byt_cr() because
> it requires the platform device, plus I think it might be better to
> differentiate the messages in the kernel log..)
> 
> --- a/sound/soc/intel/atom/sst/sst_acpi.c
> +++ b/sound/soc/intel/atom/sst/sst_acpi.c
> @@ -337,6 +337,16 @@ static int sst_acpi_probe(struct platform_device *pdev)
>   	if (!((ret < 0) || (bytcr == false))) {
>   		dev_info(dev, "Detected Baytrail-CR platform\n");
> 
>   		/* override resource info */
>   		byt_rvp_platform_data.res_info = &bytcr_res_info;
> +	} else if (platform_get_resource(pdev, IORESOURCE_IRQ, 5) == NULL) {
> +		/*
> +		 * Some devices detected as BYT-T have only a single IRQ listed.
> +		 * In this case, platform_get_irq with index 5 will return -ENXIO.
> +		 * Fall back to the BYT-CR resource info to use the correct IRQ.
> +		 */
> +		dev_info(dev, "Falling back to Baytrail-CR platform\n");
> +
> +		/* override resource info */
> +		byt_rvp_platform_data.res_info = &bytcr_res_info;
>   	}
> 
>>
>> 2) the test would affect all existing devices, and there's so much hardware
>> proliferation that proving this change in harmless might be difficult. I
>> personally only have one BYT-T (ASus T100) device left and it's not very
>> reliable. Hans seems to have a ton of devices but they are mostly Byt-Cr?
>>
> 
> With the updated patch above I believe there is literally no way this
> can break sound on any device. The condition only evaluates to true if
> SST would normally fail to probe later anyway.
> 
> I have tested the patch above on my device with:
>   - as-is, without any modifications:
>      -> "Falling back to Baytrail-CR platform", sound now working
>   - a simulated "BYT-T" device: (copied the IRQs from the DSDT of the T100TA)
>      -> "BYT-CR not detected" - uses 5th IRQ, sound working
>   - a simulated "BYT-CR" device (made is_byt_cr() return "true" and
>     copied the IRQs from the DSDT of the T100TAF)
>      -> "Detected Baytrail-CR platform" - uses IRQ at index 0, sound working
> 
> Let me know what you think!

Sounds good, playing with resources is what I had in mind rather than an 
interrupt count which isn't necessarily safe. The only improvement I 
would suggest is to add this test inside of is_byt_cr(). This routine 
will be moved as a helper outside of sst_acpi to be reused for SOF, so 
if we can make this test more self-contained it's more future-proof.