linux-kernel - Re: [PATCH 2/2] remoteproc: imx_dsp_rproc: add module parameter to ignore ready flag from remote processor

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Message-ID: <ZLa0MqKvg1W3mx/7@p14s>
Date:   Tue, 18 Jul 2023 09:48:02 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Iuliana Prodan <iuliana.prodan@....com>
Cc:     "Iuliana Prodan (OSS)" <iuliana.prodan@....nxp.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        "S.J. Wang" <shengjiu.wang@....com>,
        Fabio Estevam <festevam@...il.com>,
        Daniel Baluta <daniel.baluta@....com>,
        Mpuaudiosw <Mpuaudiosw@....com>, linux-imx <linux-imx@....com>,
        linux-remoteproc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        LnxRevLi <LnxRevLi@....com>
Subject: Re: [PATCH 2/2] remoteproc: imx_dsp_rproc: add module parameter to
 ignore ready flag from remote processor

On Tue, Jul 18, 2023 at 11:30:43AM +0300, Iuliana Prodan wrote:
> Hi Mathieu,
> 
> On 7/17/2023 8:34 PM, Mathieu Poirier wrote:
> > Hi Iuliana,
> > 
> > On Thu, Jul 13, 2023 at 01:42:51AM +0300, Iuliana Prodan (OSS) wrote:
> > > From: Iuliana Prodan <iuliana.prodan@....com>
> > > 
> > > There are cases when we want to test samples that do not
> > > reply with FW READY message, after fw is loaded and the
> > > remote processor started.
> > This seems like a bug to me - where is this FW comes from?
> The firmware is a generic sample from Zephyr repo: https://github.com/zephyrproject-rtos/zephyr/tree/main/samples/subsys/ipc/openamp_rsc_table
> 
> There is no bug, this is how the application was written.

But how did it ever worked before?  And how does having a module flag to
characterize each FW implementation that springs up in the field can scale (and
be maintainable)?

> 
> Rather than modifying a generic sample for i.MX usecase, I prefer doing an
> "insmod imx_dsp_rproc.ko ignore_dsp_ready=1" just for this sample.

We already have a "no_mailbox" flag for cases where the FW doesn't need to
communicate with the main processor.  What happens when some FW implementation
requires a three-way handshake?  How many flags do we spin off?

As I said above this approach is not sustainable.  I suggest to either fix the
FW (it doesn't work with upstream in its present form anyway) or start using the
config space as described here [1] to dynamically probe the characteristics of
the FW being loaded.  Whichever option you chose, the FW needs to be updated and
the former is a lot more simple.

Thanks,
Mathieu

[1]. https://elixir.bootlin.com/linux/latest/source/include/linux/remoteproc.h#L298

> 
> Thanks,
> Iulia
> 
> > > In these cases, do not wait for a confirmation from the remote processor
> > > at start.
> > > 
> > > Added "ignore_dsp_ready" flag while inserting the module to ignore
> > > remote processor reply after start.
> > > By default, this is off - do not ignore reply from rproc.
> > > 
> > > Signed-off-by: Iuliana Prodan <iuliana.prodan@....com>
> > > 
> > > ---
> > > This was discovered while testing openamp_rsc_table sample from Zephyr
> > > repo (https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fzephyrproject-rtos%2Fzephyr%2Ftree%2Fmain%2Fsamples%2Fsubsys%2Fipc%2Fopenamp_rsc_table&data=05%7C01%7Ciuliana.prodan%40nxp.com%7C4779cb20393e4af08a9408db86ec191e%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C638252120814415013%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=iCjvv8wr3sQ4CEXFcXDsW0VSw5RXr1ASw7LN2J08SXE%3D&reserved=0).
> > > 
> > > We have IPC, but the remote proc doesn't send a FW_READY reply.
> > > ---
> > >   drivers/remoteproc/imx_dsp_rproc.c | 15 +++++++++++++++
> > >   1 file changed, 15 insertions(+)
> > > 
> > > diff --git a/drivers/remoteproc/imx_dsp_rproc.c b/drivers/remoteproc/imx_dsp_rproc.c
> > > index b5634507d953..ed89de2f3b98 100644
> > > --- a/drivers/remoteproc/imx_dsp_rproc.c
> > > +++ b/drivers/remoteproc/imx_dsp_rproc.c
> > > @@ -36,7 +36,13 @@ module_param_named(no_mailboxes, no_mailboxes, int, 0644);
> > >   MODULE_PARM_DESC(no_mailboxes,
> > >   		 "There is no mailbox between cores, so ignore remote proc reply after start, default is 0 (off).");
> > > +static unsigned int imx_dsp_rproc_ignore_ready;
> > > +module_param_named(ignore_dsp_ready, imx_dsp_rproc_ignore_ready, int, 0644);
> > > +MODULE_PARM_DESC(ignore_dsp_ready,
> > > +		 "Ignore remote proc reply after start, default is 0 (off).");
> > > +
> > >   #define REMOTE_IS_READY				BIT(0)
> > > +#define REMOTE_IGNORE_READY_REPLY	BIT(1)
> > >   #define REMOTE_READY_WAIT_MAX_RETRIES		500
> > >   /* att flags */
> > > @@ -296,6 +302,12 @@ static int imx_dsp_rproc_ready(struct rproc *rproc)
> > >   	if (!priv->rxdb_ch)
> > >   		return 0;
> > > +	/*
> > > +	 * FW_READY reply is optional/ignored, so don't wait for it.
> > > +	 */
> > > +	if (priv->flags & REMOTE_IGNORE_READY_REPLY)
> > > +		return 0;
> > > +
> > >   	for (i = 0; i < REMOTE_READY_WAIT_MAX_RETRIES; i++) {
> > >   		if (priv->flags & REMOTE_IS_READY)
> > >   			return 0;
> > > @@ -1119,6 +1131,9 @@ static int imx_dsp_rproc_probe(struct platform_device *pdev)
> > >   	else
> > >   		imx_dsp_rproc_mbox_init = imx_dsp_rproc_mbox_alloc;
> > > +	if (imx_dsp_rproc_ignore_ready)
> > > +		priv->flags |= REMOTE_IGNORE_READY_REPLY;
> > > +
> > >   	dev_set_drvdata(dev, rproc);
> > >   	INIT_WORK(&priv->rproc_work, imx_dsp_rproc_vq_work);
> > > -- 
> > > 2.17.1
> > >