linux-kernel - Re: [PATCH v5 1/3] remoteproc: add support for co-processor loaded and booted before kernel

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Date:   Thu, 13 Feb 2020 18:55:12 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Arnaud Pouliquen <arnaud.pouliquen@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-remoteproc@...r.kernel.org, devicetree@...r.kernel.org,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Loic PALLARDY <loic.pallardy@...com>,
        Suman Anna <s-anna@...com>,
        Fabien DESSENNE <fabien.dessenne@...com>,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH v5 1/3] remoteproc: add support for co-processor loaded
 and booted before kernel

On Tue 11 Feb 09:42 PST 2020, Arnaud Pouliquen wrote:

> From: Loic Pallardy <loic.pallardy@...com>
> 
> Remote processor could boot independently or be loaded/started before
> Linux kernel by bootloader or any firmware.
> This patch introduces a new property in rproc core, named skip_fw_load,
> to be able to allocate resources and sub-devices like vdev and to
> synchronize with current state without loading firmware from file system.

This sentence describes the provided patch.

As I expressed in the earlier version, in order to support remoteprocs
that doesn't need firmware loading, e.g. running from some ROM or
dedicated flash storage etc, this patch looks really good.

> It is platform driver responsibility to implement the right firmware
> load ops according to HW specificities.

But this last sentence describes a remoteproc that indeed needs
firmware and that the purpose of this patch is to work around the core's
handling of the firmware.

> 
> Signed-off-by: Loic Pallardy <loic.pallardy@...com>
> Acked-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...com>
> ---
>  drivers/remoteproc/remoteproc_core.c | 67 ++++++++++++++++++++++------
>  include/linux/remoteproc.h           |  2 +
>  2 files changed, 55 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
[..]
> @@ -1758,11 +1779,20 @@ int rproc_boot(struct rproc *rproc)
>  
>  	dev_info(dev, "powering up %s\n", rproc->name);
>  
> -	/* load firmware */
> -	ret = request_firmware(&firmware_p, rproc->firmware, dev);
> -	if (ret < 0) {
> -		dev_err(dev, "request_firmware failed: %d\n", ret);
> -		goto downref_rproc;
> +	if (!rproc->skip_fw_load) {
> +		/* load firmware */
> +		ret = request_firmware(&firmware_p, rproc->firmware, dev);
> +		if (ret < 0) {
> +			dev_err(dev, "request_firmware failed: %d\n", ret);
> +			goto downref_rproc;
> +		}
> +	} else {
> +		/*
> +		 * Set firmware name pointer to null as remoteproc core is not
> +		 * in charge of firmware loading
> +		 */
> +		kfree(rproc->firmware);
> +		rproc->firmware = NULL;

As stated before, I think it would be more appropriate to allow a
remoteproc driver for hardware that shouldn't have firmware loaded to
never set rproc->firmware.

And I'm still curious how you're dealing with a crash or a restart on
this remoteproc. Don't you need to reload your firmware in these
circumstances? Do you perhaps have a remoteproc that's both
"already_booted" and "skip_fw_load"?

>  	}
>  
>  	ret = rproc_fw_boot(rproc, firmware_p);
> @@ -1916,8 +1946,17 @@ int rproc_add(struct rproc *rproc)
>  	/* create debugfs entries */
>  	rproc_create_debug_dir(rproc);
>  
> -	/* if rproc is marked always-on, request it to boot */
> -	if (rproc->auto_boot) {
> +	if (rproc->skip_fw_load) {
> +		/*
> +		 * If rproc is marked already booted, no need to wait
> +		 * for firmware.
> +		 * Just handle associated resources and start sub devices
> +		 */

Again, this describes a system where the remoteproc is already booted,
not a remoteproc that doesn't need firmware loading.

Regards,
Bjorn