Re: [PATCH 2/3] remoteproc: k3-r5: Acquire mailbox handle during probe

[Andrew Davis <afd@ti.com>]

On 5/30/24 4:07 AM, Beleswar Padhi wrote:
> Acquire the mailbox handle during device probe and do not release handle
> in stop/detach routine or error paths. This removes the redundant
> requests for mbox handle later during rproc start/attach. This also
> allows to defer remoteproc driver's probe if mailbox is not probed yet.
> 
> Signed-off-by: Beleswar Padhi <b-padhi@ti.com>
> ---
>   drivers/remoteproc/ti_k3_r5_remoteproc.c | 66 ++++++++----------------
>   1 file changed, 21 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/remoteproc/ti_k3_r5_remoteproc.c b/drivers/remoteproc/ti_k3_r5_remoteproc.c
> index 26362a509ae3..157e8fd57665 100644
> --- a/drivers/remoteproc/ti_k3_r5_remoteproc.c
> +++ b/drivers/remoteproc/ti_k3_r5_remoteproc.c
> @@ -391,6 +391,7 @@ static int k3_r5_rproc_request_mbox(struct rproc *rproc)
>   	struct mbox_client *client = &kproc->client;
>   	struct device *dev = kproc->dev;
>   	int ret;
> +	long err;
>   
>   	client->dev = dev;
>   	client->tx_done = NULL;
> @@ -400,10 +401,9 @@ static int k3_r5_rproc_request_mbox(struct rproc *rproc)
>   
>   	kproc->mbox = mbox_request_channel(client, 0);
>   	if (IS_ERR(kproc->mbox)) {
> -		ret = -EBUSY;
> -		dev_err(dev, "mbox_request_channel failed: %ld\n",
> -			PTR_ERR(kproc->mbox));
> -		return ret;
> +		err = PTR_ERR(kproc->mbox);
> +		dev_err(dev, "mbox_request_channel failed: %ld\n", err);
> +		return (err == -EPROBE_DEFER) ? -EPROBE_DEFER : -EBUSY;

Why turn all other errors into EBUSY? If you just return the error as-is you
can simply make these 3 lines just:

return dev_err_probe(dev, PTR_ERR(kproc->mbox), "mbox_request_channel failed\n");

>   	}
>   
>   	/*
> @@ -552,10 +552,6 @@ static int k3_r5_rproc_start(struct rproc *rproc)
>   	u32 boot_addr;
>   	int ret;
>   
> -	ret = k3_r5_rproc_request_mbox(rproc);
> -	if (ret)
> -		return ret;
> -
>   	boot_addr = rproc->bootaddr;
>   	/* TODO: add boot_addr sanity checking */
>   	dev_dbg(dev, "booting R5F core using boot addr = 0x%x\n", boot_addr);
> @@ -564,7 +560,7 @@ static int k3_r5_rproc_start(struct rproc *rproc)
>   	core = kproc->core;
>   	ret = ti_sci_proc_set_config(core->tsp, boot_addr, 0, 0);
>   	if (ret)
> -		goto put_mbox;
> +		goto out;

The label "out" doesn't do anything, just directly `return ret;` here and
in the other cases below.

>   
>   	/* unhalt/run all applicable cores */
>   	if (cluster->mode == CLUSTER_MODE_LOCKSTEP) {
> @@ -581,12 +577,12 @@ static int k3_r5_rproc_start(struct rproc *rproc)
>   			dev_err(dev, "%s: can not start core 1 before core 0\n",
>   				__func__);
>   			ret = -EPERM;
> -			goto put_mbox;
> +			goto out;
>   		}
>   
>   		ret = k3_r5_core_run(core);
>   		if (ret)
> -			goto put_mbox;
> +			goto out;
>   	}
>   
>   	return 0;
> @@ -596,8 +592,7 @@ static int k3_r5_rproc_start(struct rproc *rproc)
>   		if (k3_r5_core_halt(core))
>   			dev_warn(core->dev, "core halt back failed\n");
>   	}
> -put_mbox:
> -	mbox_free_channel(kproc->mbox);
> +out:
>   	return ret;
>   }
>   
> @@ -658,8 +653,6 @@ static int k3_r5_rproc_stop(struct rproc *rproc)
>   			goto out;
>   	}
>   
> -	mbox_free_channel(kproc->mbox);
> -
>   	return 0;
>   
>   unroll_core_halt:
> @@ -674,42 +667,21 @@ static int k3_r5_rproc_stop(struct rproc *rproc)
>   /*
>    * Attach to a running R5F remote processor (IPC-only mode)
>    *
> - * The R5F attach callback only needs to request the mailbox, the remote
> - * processor is already booted, so there is no need to issue any TI-SCI
> - * commands to boot the R5F cores in IPC-only mode. This callback is invoked
> - * only in IPC-only mode.
> + * The R5F attach callback is a NOP. The remote processor is already booted, and
> + * all required resources have been acquired during probe routine, so there is
> + * no need to issue any TI-SCI commands to boot the R5F cores in IPC-only mode.
> + * This callback is invoked only in IPC-only mode and exists for sanity sake.
>    */
> -static int k3_r5_rproc_attach(struct rproc *rproc)
> -{
> -	struct k3_r5_rproc *kproc = rproc->priv;
> -	struct device *dev = kproc->dev;
> -	int ret;
> -
> -	ret = k3_r5_rproc_request_mbox(rproc);
> -	if (ret)
> -		return ret;
> -
> -	dev_info(dev, "R5F core initialized in IPC-only mode\n");
> -	return 0;
> -}
> +static int k3_r5_rproc_attach(struct rproc *rproc) { return 0; }
>   
>   /*
>    * Detach from a running R5F remote processor (IPC-only mode)
>    *
> - * The R5F detach callback performs the opposite operation to attach callback
> - * and only needs to release the mailbox, the R5F cores are not stopped and
> - * will be left in booted state in IPC-only mode. This callback is invoked
> - * only in IPC-only mode.
> + * The R5F detach callback is a NOP. The R5F cores are not stopped and will be
> + * left in booted state in IPC-only mode. This callback is invoked only in
> + * IPC-only mode and exists for sanity sake.
>    */
> -static int k3_r5_rproc_detach(struct rproc *rproc)
> -{
> -	struct k3_r5_rproc *kproc = rproc->priv;
> -	struct device *dev = kproc->dev;
> -
> -	mbox_free_channel(kproc->mbox);
> -	dev_info(dev, "R5F core deinitialized in IPC-only mode\n");
> -	return 0;
> -}
> +static int k3_r5_rproc_detach(struct rproc *rproc) { return 0; }

Do we still need to disable the mbox channel somehow here to prevent
receiving more messages from the detached core?

>   
>   /*
>    * This function implements the .get_loaded_rsc_table() callback and is used
> @@ -1277,6 +1249,10 @@ static int k3_r5_cluster_rproc_init(struct platform_device *pdev)
>   		kproc->rproc = rproc;
>   		core->rproc = rproc;
>   
> +		ret = k3_r5_rproc_request_mbox(rproc);

Now that we get the channel here in init you'll want to add a matching
mbox_free_channel() call to k3_r5_cluster_rproc_exit().

Andrew

> +		if (ret)
> +			return ret;
> +
>   		ret = k3_r5_rproc_configure_mode(kproc);
>   		if (ret < 0)
>   			goto err_config;