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Subject: Re: [PATCH] platform/chrome: cros_ec_typec: Handle NULL EC pointer
 during probe.
To:     Daniil Lunev <dlunev@chromium.org>,
        Prashant Malani <pmalani@chromium.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Benson Leung <bleung@chromium.org>,
        Guenter Roeck <groeck@chromium.org>
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From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <d5369956-aca4-2c40-3300-d86151847bbc@collabora.com>
Date:   Tue, 5 May 2020 22:36:37 +0200
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Hi.

On 1/5/20 5:22, Daniil Lunev wrote:
> Hi Prashant,
> I do not think it is present. Thinking about it, I do not think it
> shall be an issue on any released device as it will have either a
> firmware which wouldn't even trigger the typec probe or the one after
> the hierarchy fix. Likely I just got a firmware which was somewhere in
> between those two (As I did some unrelated FW testing). So, yes,
> probably putting this upstream is not necessary, though IMO more
> sanity checks - especially on non-critical run-once paths - are always
> better than having a kernel panic lingering around the corner, not
> like I am insisting on pushing the patch though with all the info, up
> to Enric.

I'd prefer to not push the patch. If at some point this is starts of being
possible we will catch soon.

Thank you,
 Enric

> Cheers,
> Daniil
> 
> On Fri, May 1, 2020 at 10:56 AM Prashant Malani <pmalani@chromium.org> wrote:
>>
>> Hi Daniil,
>>
>> On Fri, May 01, 2020 at 10:15:18AM +1000, Daniil Lunev wrote:
>>> On the official revision of coreboot for hatch it doesn't even try to
>>> load Type C. However it gives some warning messages from
>>> cros-usbpd-notify-acpi about EC, So I wonder why the check of the same
>>> type is not appropriate in the typec driver?
>>
>> I think the difference is that GOOG0003 is already present on shipped /
>> official versions of coreboot (so not having that check can cause
>> existing release images/devices to crash), whereas for GOOG0014 that is / isn't the case.
>>
>> Is GOOG0014 present on the official release coreboot image for this
>> device? If so, what's its path (/sys/bus/acpi/devices/<HID>/path) ?
>>
>> Best regards,
>>
>> -Prashant
>>>
>>> ../chrome/cros_usbpd_notify.c
>>>
>>> /* Get the EC device pointer needed to talk to the EC. */
>>> ec_dev = dev_get_drvdata(dev->parent);
>>> if (!ec_dev) {
>>> /*
>>> * We continue even for older devices which don't have the
>>> * correct device heirarchy, namely, GOOG0003 is a child
>>> * of GOOG0004.
>>> */
>>> dev_warn(dev, "Couldn't get Chrome EC device pointer.\n");
>>> }
>>>
>>>
>>> # dmesg
>>> ...
>>> [    8.513351] cros-ec-spi spi-PRP0001:02: EC failed to respond in time
>>> [    8.722072] cros-ec-spi spi-PRP0001:02: EC failed to respond in time
>>> [    8.729271] cros-ec-spi spi-PRP0001:02: Cannot identify the EC: error -110
>>> [    8.736966] cros-ec-spi spi-PRP0001:02: cannot register EC,
>>> fallback to spidev
>>> [    8.767017] cros_ec_lpcs GOOG0004:00: Chrome EC device registered
>>> [    8.807537] cros-usbpd-notify-acpi GOOG0003:00: Couldn't get Chrome
>>> EC device pointer.
>>> ...
>>>
>>> On Fri, May 1, 2020 at 2:17 AM Prashant Malani <pmalani@chromium.org> wrote:
>>>>
>>>> Hi Enric,
>>>>
>>>> On Thu, Apr 30, 2020 at 8:26 AM Enric Balletbo i Serra
>>>> <enric.balletbo@collabora.com> wrote:
>>>>>
>>>>> Hi Prashant,
>>>>>
>>>>> On 30/4/20 2:43, Prashant Malani wrote:
>>>>>> On Wed, Apr 29, 2020 at 5:38 PM Daniil Lunev <dlunev@chromium.org> wrote:
>>>>>>>
>>>>>>> [to make it appear on the mailing list as I didn't realize I was in
>>>>>>> hypertext sending mode]
>>>>>>>
>>>>>>> On Thu, Apr 30, 2020 at 10:11 AM Daniil Lunev <dlunev@chromium.org> wrote:
>>>>>>>>
>>>>>>>> Hi Enric.
>>>>>>>> I encountered the issue on a Hatch device when trying running 5.4 kernel on that. After talking to Prashant it seems that any device with coreboot built before a certain point (a particular fix for device hierarchy in ACPI tables of Chrome devices which happened in mid-April) will not be able to correctly initialize the driver and will get a kernel panic trying to do so.
>>>>>>
>>>>>> A clarifying detail here: This should not be seen in any current
>>>>>> *production* device. No prod device firmware will carry the erroneous
>>>>>> ACPI device entry.
>>>>>>
>>>>>
>>>>> Thanks for the clarification. Then, I don't think we need to upstream this. This
>>>>> kind of "defensive-programming" it's not something that should matter to upstream.
>>>>
>>>> Actually, on second thought, I am not 100% sure about this:
>>>> Daniil, is the erroneous ACPI device on a *production* firmware for
>>>> this device (I'm not sure about the vintage of that device's BIOS)?
>>>>
>>>> My apologies for the confusion, Enric and Daniil; but would be good to
>>>> get clarification from Daniil.
>>>>
>>>> Best regards,
>>>>>
>>>>> Thanks,
>>>>>  Enric
>>>>>
>>>>>
>>>>>>>> Thanks,
>>>>>>>> Daniil
>>>>>>>>
>>>>>>>> On Thu, Apr 30, 2020 at 7:58 AM Enric Balletbo i Serra <enric.balletbo@collabora.com> wrote:
>>>>>>>>>
>>>>>>>>> Hi Daniil,
>>>>>>>>>
>>>>>>>>> Thank you for the patch.
>>>>>>>>>
>>>>>>>>> On 28/4/20 3:02, Daniil Lunev wrote:
>>>>>>>>>> Missing EC in device hierarchy causes NULL pointer to be returned to the
>>>>>>>>>> probe function which leads to NULL pointer dereference when trying to
>>>>>>>>>> send a command to the EC. This can be the case if the device is missing
>>>>>>>>>> or incorrectly configured in the firmware blob. Even if the situation
>>>>>>>>>
>>>>>>>>> There is any production device with a buggy firmware outside? Or this is just
>>>>>>>>> for defensive programming while developing the firmware? Which device is
>>>>>>>>> affected for this issue?
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>  Enric
>>>>>>>>>
>>>>>>>>>> occures, the driver shall not cause a kernel panic as the condition is
>>>>>>>>>> not critical for the system functions.
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Daniil Lunev <dlunev@chromium.org>
>>>>>>>>>> ---
>>>>>>>>>>
>>>>>>>>>>  drivers/platform/chrome/cros_ec_typec.c | 5 +++++
>>>>>>>>>>  1 file changed, 5 insertions(+)
>>>>>>>>>>
>>>>>>>>>> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
>>>>>>>>>> index 874269c07073..30d99c930445 100644
>>>>>>>>>> --- a/drivers/platform/chrome/cros_ec_typec.c
>>>>>>>>>> +++ b/drivers/platform/chrome/cros_ec_typec.c
>>>>>>>>>> @@ -301,6 +301,11 @@ static int cros_typec_probe(struct platform_device *pdev)
>>>>>>>>>>
>>>>>>>>>>       typec->dev = dev;
>>>>>>>>>>       typec->ec = dev_get_drvdata(pdev->dev.parent);
>>>>>>>>>> +     if (!typec->ec) {
>>>>>>>>>> +             dev_err(dev, "Failed to get Cros EC data\n");
>>>>>>>>>> +             return -EINVAL;
>>>>>>>>>> +     }
>>>>>>>>>> +
>>>>>>>>>>       platform_set_drvdata(pdev, typec);
>>>>>>>>>>
>>>>>>>>>>       ret = cros_typec_get_cmd_version(typec);
>>>>>>>>>>