[alsa-devel] [PATCH 2/3] ASoC: SOF: imx: Add i.MX8 HW support

[Daniel Baluta]

Hi Cezary,

On Sat, Aug 17, 2019 at 6:22 PM Cezary Rojewski
<cezary.rojewski at intel.com> wrote:
>
> On 2019-08-15 17:44, Pierre-Louis Bossart wrote:
> > From: Daniel Baluta <daniel.baluta at nxp.com>
> >
> > Add support for the audio DSP hardware found on NXP i.MX8 platform.
> >
> > Signed-off-by: Daniel Baluta <daniel.baluta at nxp.com>
> > Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> > +static void imx8_get_reply(struct snd_sof_dev *sdev)
> > +{
> > +     struct snd_sof_ipc_msg *msg = sdev->msg;
> > +     struct sof_ipc_reply reply;
> > +     int ret = 0;
> > +
> > +     if (!msg) {
> > +             dev_warn(sdev->dev, "unexpected ipc interrupt\n");
> > +             return;
> > +     }
> > +
> > +     /* get reply */
> > +     sof_mailbox_read(sdev, sdev->host_box.offset, &reply, sizeof(reply));
> > +
> > +     if (reply.error < 0) {
> > +             memcpy(msg->reply_data, &reply, sizeof(reply));
> > +             ret = reply.error;
> > +     } else {
> > +             /* reply has correct size? */
> > +             if (reply.hdr.size != msg->reply_size) {
> > +                     dev_err(sdev->dev, "error: reply expected %zu got %u bytes\n",
> > +                             msg->reply_size, reply.hdr.size);
> > +                     ret = -EINVAL;
> > +             }
> > +
> > +             /* read the message */
> > +             if (msg->reply_size > 0)
> > +                     sof_mailbox_read(sdev, sdev->host_box.offset,
> > +                                      msg->reply_data, msg->reply_size);
> > +     }
> > +
> > +     msg->reply_error = ret;
> > +}
>
> Assuming reply.hdr.size is coming from HW IPC regs, msg object is
> representing application side - SW, kernel. If so, is msg->reply_size
> value an estimated size (which can be overestimated since exact size may
> be unknown by the host) -or- the exact size of incoming IPC reply?
>

I would say msg->reply_size is the exact size of incoming IPC. At least for this
example:

Look at sound/soc/sof/pcm.c

sof_pcm_trigger

-> sof_ipc_tx_message(..,..,&reply, sizeof(reply))

msg->reply_size = sizeof(reply).

On the firmware side:

https://github.com/thesofproject/sof/blob/master/src/ipc/handler.c#L912
reply.rhdr.hdr.size = sizeof(reply);

> The estimated-case is usually permissive as long as assumed size is >=
> reply.hdr.size - dev_err needed. In the exact-case, it should be viewed
> as a requirement. If such "requirement" fails, is it valid to read
> mailbox regardless? Is this to extract some error-debug payload sent by FW?
>
> Just curious, please feel free to correct me here, Pierre.

If you think an improvement can be done, please send a patch :).

thanks,
Daniel.