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References: <20200410162305.76638-1-mathewk@chromium.org> <c0e0c052-17bd-fea7-a4a8-07b4afbe56bd@collabora.com>
In-Reply-To: <c0e0c052-17bd-fea7-a4a8-07b4afbe56bd@collabora.com>
From:   Jett Rink <jettrink@chromium.org>
Date:   Tue, 14 Apr 2020 10:45:47 -0600
Message-ID: <CAK+PMK51SOH_61ci7zCEDHFJ9yiN=J8fYh2WFhj82=v4qYCV1Q@mail.gmail.com>
Subject: Re: [PATCH v2 1/2] platform/chrome: cros_ec_ishtp: skip old cros_ec responses
To:     Enric Balletbo i Serra <enric.balletbo@collabora.com>
Cc:     Mathew King <mathewk@chromium.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Benson Leung <bleung@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        Rushikesh S Kadam <rushikesh.s.kadam@intel.com>
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Thank you!


On Tue, Apr 14, 2020 at 10:24 AM Enric Balletbo i Serra
<enric.balletbo@collabora.com> wrote:
>
> Hi Jett and Mathew,
>
> Thank you for the patch
>
> On 10/4/20 18:23, Mathew King wrote:
> > From: Jett Rink <jettrink@chromium.org>
> >
> > The ISHTP layer can give us old responses that we already gave up on. We
> > do not want to interpret these old responses as the current response we
> > are waiting for.
> >
> > The cros_ish should only have one request in flight at a time. We send
> > the request and wait for the response from the ISH. If the ISH is too
> > slow to respond we give up on that request and we can send a new
> > request. The ISH may still send the response to the request that timed
> > out and without this we treat the old response as the response to the
> > current command. This is a condition that should not normally happen but
> > it has been observed with a bad ISH image. So add a token to the request
> > header which is copied into the response header when the ISH processes
> > the message to ensure that response is for the current request.
> >
> > Signed-off-by: Jett Rink <jettrink@chromium.org>
> > Signed-off-by: Mathew King <mathewk@chromium.org>
>
> Queued for 5.8
>
> > ---
> > v2: - Change from using id to token
> >     - Reword the commit message
> > ---
> >  drivers/platform/chrome/cros_ec_ishtp.c | 32 ++++++++++++++++++-------
> >  1 file changed, 23 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_ishtp.c b/drivers/platform/chrome/cros_ec_ishtp.c
> > index 93a71e93a2f1..e673a7f738fc 100644
> > --- a/drivers/platform/chrome/cros_ec_ishtp.c
> > +++ b/drivers/platform/chrome/cros_ec_ishtp.c
> > @@ -48,7 +48,8 @@ static const guid_t cros_ish_guid =
> >  struct header {
> >       u8 channel;
> >       u8 status;
> > -     u8 reserved[2];
> > +     u8 token;
> > +     u8 reserved;
> >  } __packed;
> >
> >  struct cros_ish_out_msg {
> > @@ -90,6 +91,7 @@ static DECLARE_RWSEM(init_lock);
> >   * data exceeds this value, we log an error.
> >   * @size: Actual size of data received from firmware.
> >   * @error: 0 for success, negative error code for a failure in process_recv().
> > + * @token: Expected token for response that we are waiting on.
> >   * @received: Set to true on receiving a valid firmware      response to host command
> >   * @wait_queue: Wait queue for host to wait for firmware response.
> >   */
> > @@ -98,6 +100,7 @@ struct response_info {
> >       size_t max_size;
> >       size_t size;
> >       int error;
> > +     u8 token;
> >       bool received;
> >       wait_queue_head_t wait_queue;
> >  };
> > @@ -162,6 +165,7 @@ static int ish_send(struct ishtp_cl_data *client_data,
> >                   u8 *out_msg, size_t out_size,
> >                   u8 *in_msg, size_t in_size)
> >  {
> > +     static u8 next_token;
> >       int rv;
> >       struct header *out_hdr = (struct header *)out_msg;
> >       struct ishtp_cl *cros_ish_cl = client_data->cros_ish_cl;
> > @@ -174,8 +178,11 @@ static int ish_send(struct ishtp_cl_data *client_data,
> >       client_data->response.data = in_msg;
> >       client_data->response.max_size = in_size;
> >       client_data->response.error = 0;
> > +     client_data->response.token = next_token++;
> >       client_data->response.received = false;
> >
> > +     out_hdr->token = client_data->response.token;
> > +
> >       rv = ishtp_cl_send(cros_ish_cl, out_msg, out_size);
> >       if (rv) {
> >               dev_err(cl_data_to_dev(client_data),
> > @@ -249,17 +256,23 @@ static void process_recv(struct ishtp_cl *cros_ish_cl,
> >
> >       switch (in_msg->hdr.channel) {
> >       case CROS_EC_COMMAND:
> > -             /* Sanity check */
> > -             if (!client_data->response.data) {
> > +             if (client_data->response.received) {
> >                       dev_err(dev,
> > -                             "Receiving buffer is null. Should be allocated by calling function\n");
> > -                     client_data->response.error = -EINVAL;
> > -                     goto error_wake_up;
> > +                             "Previous firmware message not yet processed\n");
> > +                     goto end_error;
> >               }
> >
> > -             if (client_data->response.received) {
> > +             if (client_data->response.token != in_msg->hdr.token) {
> > +                     dev_err_ratelimited(dev,
> > +                                         "Dropping old response token %d\n",
> > +                                         in_msg->hdr.token);
> > +                     goto end_error;
> > +             }
> > +
> > +             /* Sanity check */
> > +             if (!client_data->response.data) {
> >                       dev_err(dev,
> > -                             "Previous firmware message not yet processed\n");
> > +                             "Receiving buffer is null. Should be allocated by calling function\n");
> >                       client_data->response.error = -EINVAL;
> >                       goto error_wake_up;
> >               }
> > @@ -289,9 +302,10 @@ static void process_recv(struct ishtp_cl *cros_ish_cl,
> >               memcpy(client_data->response.data,
> >                      rb_in_proc->buffer.data, data_len);
> >
> > +error_wake_up:
> >               /* Set flag before waking up the caller */
> >               client_data->response.received = true;
> > -error_wake_up:
> > +
> >               /* Wake the calling thread */
> >               wake_up_interruptible(&client_data->response.wait_queue);
> >
> >