linux-kernel - Re: regression: twl4030 audio/clock stopped working in v4.16

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Date:   Thu, 5 Apr 2018 14:56:15 +0300
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
CC:     Discussions about the Letux Kernel <letux-kernel@...nphoenux.org>,
        Tony Lindgren <tony@...mide.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>
Subject: Re: regression: twl4030 audio/clock stopped working in v4.16

Nikolaus,

On 2018-04-05 14:05, Peter Ujfalusi wrote:
> Nikolaus,
> 
> can you CC me also, I have almost missed this...
> 
> On 2018-04-04 21:29, H. Nikolaus Schaller wrote:
>> Hi Peter,
>> I just noticed a problem in v4.16 kernels with twl4030 audio and vibra driver no longer working.
>>
>> Tracing it back shows that it already did appear in v4.16-rc1 and wasn't fixed up to v4.16.0.
>> Kernel v4.15.9 (the latest one where I have a binary) works.
> 
> v4.16 works just fine on beagle-xm (including audio), omap2plus_defconfig.
> 
>> The symptoms are:
>>
>> [    1.557342] twl4030-audio 48070000.i2c:twl@48:audio: Invalid audio_mclk
>> [    1.564788] twl4030-audio: probe of 48070000.i2c:twl@48:audio failed with error -22
>> [    1.839141] TWL4030: HFCLK is not configured
> 
> Hrm, the order looks a bit weird, it should be
> TWL4030: HFCLK is not configured
> twl4030-audio 48070000.i2c:twl@48:audio: Invalid audio_mclk
> twl4030-audio: probe of 48070000.i2c:twl@48:audio failed with error -22
> 
> In twl4030_audio_probe() we try to get the HFCLK rate via
> twl_get_hfclk_rate(), which is reading it with:
> twl_i2c_read_u8(TWL_MODULE_PM_MASTER, &ctrl, R_CFG_BOOT);
> 
>> Those are not visible in v4.15.9. And I am not aware of any changes to the gta04 device tree.
>>
>> Do you know about this issue and a fix, before I start to bisect?
> 
> The CFG_BOOT register of twl4030 is not configured correctly for some
> reason?
> The TRM of twl4030 states that the SW should program the HFCLK_FREQ
> during boot sequence.
> 
> If it is not done, MDAC and USB should not work either. And all sorts of
> other issues might happen.
> 
> So the boot loader is not configuring the HFCLK_FREQ, for me it does as
> I have this line in the kernel log:
> [    1.472503] Skipping twl internal clock init and using bootloader
> value (unknown osc rate)
> 
> In DT the twl should have the fck clock to not depend on the bootloader
> for the HFCLK_FREQ settings. We do not have that for beagle-xm for sure.

there is a bug in twl-core for getting the clock:
https://marc.info/?l=linux-omap&m=152292879928720&w=2

and a patch for beagle-xm to add the fixed clock:
https://marc.info/?l=linux-omap&m=152292917328832&w=2

With these two, beagle-xm no longer depends on bootloader to set the
HFCLK_FREQ for twl4030.

- Péter

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