Date:   Tue, 19 Sep 2017 10:03:03 -0700
From:   Shawn N <shawnn@...omium.org>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Brian Norris <briannorris@...omium.org>,
        Olof Johansson <olof@...om.net>,
        Benson Leung <bleung@...omium.org>,
        Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org,
        Doug Anderson <dianders@...omium.org>,
        Brian Norris <computersforpeace@...il.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Gwendal Grignou <gwendal@...omium.org>,
        Enric Balletbo <enric.balletbo@...labora.co.uk>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3] platform/chrome: Use proper protocol transfer function

On Tue, Sep 19, 2017 at 9:39 AM, Jon Hunter <jonathanh@...dia.com> wrote:
>
>
> On 19/09/17 15:09, Shawn N wrote:
>> On Tue, Sep 19, 2017 at 6:44 AM, Jon Hunter <jonathanh@...dia.com> wrote:
>>>
>>> Hi Brian,
>>>
>>> On 08/09/17 21:50, Brian Norris wrote:
>>>> From: Shawn Nematbakhsh <shawnn@...omium.org>
>>>>
>>>> pkt_xfer should be used for protocol v3, and cmd_xfer otherwise. We had
>>>> one instance of these functions correct, but not the second, fall-back
>>>> case. We use the fall-back only when the first command returns an
>>>> IN_PROGRESS status, which is only used on some EC firmwares where we
>>>> don't want to constantly poll the bus, but instead back off and
>>>> sleep/retry for a little while.
>>>>
>>>> Fixes: 2c7589af3c4d ("mfd: cros_ec: add proto v3 skeleton")
>>>> Signed-off-by: Shawn Nematbakhsh <shawnn@...omium.org>
>>>> Signed-off-by: Brian Norris <briannorris@...omium.org>
>>>> Reviewed-by: Javier Martinez Canillas <javier@....samsung.com>
>>>> ---
>>>> v3:
>>>>  * Added Javier's reviewed tag
>>>>  * It's been > 8 months since [1], so why not? And hey, Benson's officially in
>>>>    MAINTAINERS now! Too bad no one told me.
>>>>
>>>>  [1] https://patchwork.kernel.org/patch/9450633/
>>>>
>>>>
>>>> v2:
>>>>  * Add Benson in 'To:'
>>>>  * make subject prefix more obvious
>>>>
>>>>  drivers/platform/chrome/cros_ec_proto.c | 8 +++++---
>>>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
>>>> index 8dfa7fcb1248..e7bbdf947bbc 100644
>>>> --- a/drivers/platform/chrome/cros_ec_proto.c
>>>> +++ b/drivers/platform/chrome/cros_ec_proto.c
>>>> @@ -60,12 +60,14 @@ static int send_command(struct cros_ec_device *ec_dev,
>>>>                       struct cros_ec_command *msg)
>>>>  {
>>>>       int ret;
>>>> +     int (*xfer_fxn)(struct cros_ec_device *ec, struct cros_ec_command *msg);
>>>>
>>>>       if (ec_dev->proto_version > 2)
>>>> -             ret = ec_dev->pkt_xfer(ec_dev, msg);
>>>> +             xfer_fxn = ec_dev->pkt_xfer;
>>>>       else
>>>> -             ret = ec_dev->cmd_xfer(ec_dev, msg);
>>>> +             xfer_fxn = ec_dev->cmd_xfer;u
>>>>
>>>> +     ret = (*xfer_fxn)(ec_dev, msg);
>>>>       if (msg->result == EC_RES_IN_PROGRESS) {
>>>>               int i;
>>>>               struct cros_ec_command *status_msg;
>>>> @@ -88,7 +90,7 @@ static int send_command(struct cros_ec_device *ec_dev,
>>>>               for (i = 0; i < EC_COMMAND_RETRIES; i++) {
>>>>                       usleep_range(10000, 11000);
>>>>
>>>> -                     ret = ec_dev->cmd_xfer(ec_dev, status_msg);
>>>> +                     ret = (*xfer_fxn)(ec_dev, status_msg);
>>>>                       if (ret < 0)
>>>>                               break;
>>>>
>>>
>>> Tegra124 Nyan-Big is currently crashing during boot with -next [0] and
>>> bisect is pointing to this commit. Reverting the above on top of -next
>>> does allow the board to boot successfully. Looks like this board is
>>> proto_version 3 but I have not looked into this any further. Let me know
>>> if you have any thoughts.
>>
>>
>> Thanks for the bug report, I'll look into this today.
>>
>>> [    1.502497] kernel BUG at drivers/platform/chrome/cros_ec_proto.c:34!
>>> 34 BUG_ON(ec_dev->proto_version != EC_HOST_REQUEST_VERSION);
>>
>> So, ec_dev->proto_version > 3? That doesn't seem right.
>
> You mean != 3, but yes. Looks like an initialisation problem, because if I
> add the following WARNING ...

I meant > 3 because we check for > 2 in send_command().

>
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index e7bbdf947bbc..ad3b3a1e8d54 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -31,6 +31,7 @@ static int prepare_packet(struct cros_ec_device *ec_dev,
>         int i;
>         u8 csum = 0;
>
> +       WARN(ec_dev->proto_version != EC_HOST_REQUEST_VERSION, "%d != %d", ec_dev->proto_version, EC_HOST_REQUEST_VERSION);
>         BUG_ON(ec_dev->proto_version != EC_HOST_REQUEST_VERSION);
>         BUG_ON(msg->outsize + sizeof(*request) > ec_dev->dout_size);
>
> ... then I see ...
>
> [    1.502495] WARNING: CPU: 0 PID: 1 at drivers/platform/chrome/cros_ec_proto.c:35 cros_ec_prepare_tx+0x190/0x1a8
> [    1.512566] 65535 != 3
>
> Any chance this is being called before the version is initialised?

It's initialized in cros_ec_query_all().

Considering your trace shows (send_command+0x20/0xd8) as a caller, I'm
guessing that we die on the first call to (*xfer_fxn):

+     ret = (*xfer_fxn)(ec_dev, msg);

That part of the change should be a NOP, I only added a function
pointer so we wouldn't have to re-check protocol_version later. The
syntax looks fine to me even after re-checking, but maybe I missed
something. Let me test on my side.

>
> Cheers
> Jon
>
> --
> nvpublic

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