Re: next/master bisection: baseline.dmesg.emerg on meson-gxbb-p200

[Jerome Brunet <jbrunet@baylibre.com>]

On Thu 19 Nov 2020 at 19:04, Guillaume Tucker <guillaume.tucker@collabora.com> wrote:

> Hi Marc,
>
> On 19/11/2020 11:58, Marc Zyngier wrote:
>> On 2020-11-19 10:26, Neil Armstrong wrote:
>>> On 19/11/2020 11:20, Marc Zyngier wrote:
>>>> On 2020-11-19 08:50, Guillaume Tucker wrote:
>>>>> Please see the automated bisection report below about some kernel
>>>>> errors on meson-gxbb-p200.
>>>>>
>>>>> Reports aren't automatically sent to the public while we're
>>>>> trialing new bisection features on kernelci.org, however this one
>>>>> looks valid.
>>>>>
>>>>> The bisection started with next-20201118 but the errors are still
>>>>> present in next-20201119.  Details for this regression:
>>>>>
>>>>>   https://kernelci.org/test/case/id/5fb6196bfd0127fd68d8d902/
>>>>>
>>>>> The first error is:
>>>>>
>>>>>   [   14.757489] Internal error: synchronous external abort: 96000210
>>>>> [#1] PREEMPT SMP
>>>>
>>>> Looks like yet another clock ordering setup. I guess different Amlogic
>>>> platforms have slightly different ordering requirements.
>>>>
>>>> Neil, do you have any idea of which platform requires which ordering?
>>>> The variability in DT and platforms is pretty difficult to follow (and
>>>> I don't think I have such board around).
>>>
>>> The requirements should be the same, here the init was done before calling
>>> dw_hdmi_probe to be sure the clocks and internals resets were deasserted.
>>> But since you boot from u-boot already enabling these, it's already active.
>>>
>>> The solution would be to revert and do some check in meson_dw_hdmi_init() to
>>> check if already enabled and do nothing.
>> 
>> A better fix seems to be this, which makes it explicit that there is
>> a dependency between some of the registers accessed from meson_dw_hdmi_init()
>> and the iahb clock.
>> 
>> Guillaume, can you give this a go on your failing box?
>
> I confirm it solves the problem.  Please add this to your fix
> patch if it's OK with you:
>
>   Reported-by: "kernelci.org bot" <bot@kernelci.org>
>   Tested-by: Guillaume Tucker <guillaume.tucker@collabora.com>
>
>
> For the record, it passed all the tests when applied on top of
> the "bad" revision found by the bisection:
>
>   http://lava.baylibre.com:10080/scheduler/alljobs?search=v5.10-rc3-1021-gb8668a2e5ea1
>
> and the exact same test on the "bad" revision without the fix
> consistently showed the error:
>
>   http://lava.baylibre.com:10080/scheduler/job/374176
>
>
> Thanks,
> Guillaume
>
>
>> diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
>> index 7f8eea494147..52af8ba94311 100644
>> --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
>> +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
>> @@ -146,6 +146,7 @@ struct meson_dw_hdmi {
>>      struct reset_control *hdmitx_ctrl;
>>      struct reset_control *hdmitx_phy;
>>      struct clk *hdmi_pclk;
>> +    struct clk *iahb_clk;
>>      struct clk *venci_clk;
>>      struct regulator *hdmi_supply;
>>      u32 irq_stat;
>> @@ -1033,6 +1034,13 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
>>      }
>>      clk_prepare_enable(meson_dw_hdmi->hdmi_pclk);
>> 
>> +    meson_dw_hdmi->iahb_clk = devm_clk_get(dev, "iahb");
>> +    if (IS_ERR(meson_dw_hdmi->iahb_clk)) {
>> +        dev_err(dev, "Unable to get iahb clk\n");
>> +        return PTR_ERR(meson_dw_hdmi->iahb_clk);
>> +    }
>> +    clk_prepare_enable(meson_dw_hdmi->iahb_clk);

If you guys are going ahead with this fix, this call to
clk_prepare_enable() needs to be balanced with clk_disable_unprepare() somehow

>> +
>>      meson_dw_hdmi->venci_clk = devm_clk_get(dev, "venci");
>>      if (IS_ERR(meson_dw_hdmi->venci_clk)) {
>>          dev_err(dev, "Unable to get venci clk\n");
>> @@ -1071,6 +1079,8 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
>> 
>>      encoder->possible_crtcs = BIT(0);
>> 
>> +    meson_dw_hdmi_init(meson_dw_hdmi);
>> +
>>      DRM_DEBUG_DRIVER("encoder initialized\n");
>> 
>>      /* Bridge / Connector */
>> @@ -1095,8 +1105,6 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
>>      if (IS_ERR(meson_dw_hdmi->hdmi))
>>          return PTR_ERR(meson_dw_hdmi->hdmi);
>> 
>> -    meson_dw_hdmi_init(meson_dw_hdmi);
>> -
>>      next_bridge = of_drm_find_bridge(pdev->dev.of_node);
>>      if (next_bridge)
>>          drm_bridge_attach(encoder, next_bridge,
>> 
>>