Re: [PATCH v4 1/1] remoteproc: add support for co-processor loaded and booted before kernel

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 28 Nov 03:33 PST 2019, Loic Pallardy wrote:

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

I was going to apply the patch, as I like what it actually does. But I'm
concerned about how you're going to use it (which you fail to show in
this single patch). Just two things below.

> Signed-off-by: Loic Pallardy <loic.pallardy@st.com>
> Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> 
> ---
> Change from v3:
> - add comment about firmware NULL pointer
> - add Mathieu Poirier Ack
> Change from v2:
> - rename property into skip_fw_load
> - update rproc_boot and rproc_fw_boot description
> - update commit message
> Change from v1:
> - Keep bool in struct rproc
> ---
>  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
> index 307df98347ba..367a7929b7a0 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1358,8 +1358,19 @@ static int rproc_start(struct rproc *rproc, const struct firmware *fw)
>  	return ret;
>  }
>  
> -/*
> - * take a firmware and boot a remote processor with it.
> +/**
> + * rproc_fw_boot() - boot specified remote processor according to specified
> + * firmware
> + * @rproc: handle of a remote processor
> + * @fw: pointer on firmware to handle
> + *
> + * Handle resources defined in resource table, load firmware and
> + * start remote processor.
> + *
> + * If firmware pointer fw is NULL, firmware is not handled by remoteproc
> + * core, but under the responsibility of platform driver.
> + *
> + * Returns 0 on success, and an appropriate error value otherwise.
>   */
>  static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
>  {
> @@ -1371,7 +1382,11 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
>  	if (ret)
>  		return ret;
>  
> -	dev_info(dev, "Booting fw image %s, size %zd\n", name, fw->size);
> +	if (fw)
> +		dev_info(dev, "Booting fw image %s, size %zd\n", name,
> +			 fw->size);
> +	else
> +		dev_info(dev, "Synchronizing with preloaded co-processor\n");

This log line implies that ops->start() doesn't actually start the
remoteproc, but it sounds like a remote proc with skip_fw_load actually
would boot the remote processor, but with some pre-existing firmware.

As such it makes more sense, in this patch, to print "Booting\n" here.


But I presume you have a platform driver with a nop start()
implementation and no ability to reload the firmware on a crash?

>  
>  	/*
>  	 * if enabling an IOMMU isn't relevant for this rproc, this is
> @@ -1718,16 +1733,22 @@ static void rproc_crash_handler_work(struct work_struct *work)
>   * rproc_boot() - boot a remote processor
>   * @rproc: handle of a remote processor
>   *
> - * Boot a remote processor (i.e. load its firmware, power it on, ...).
> + * Boot a remote processor (i.e. load its firmware, power it on, ...) from
> + * different contexts:
> + * - power off
> + * - preloaded firmware
> + * - started before kernel execution
> + * The different operations are selected thanks to properties defined by
> + * platform driver.
>   *
> - * If the remote processor is already powered on, this function immediately
> - * returns (successfully).
> + * If the remote processor is already powered on at rproc level, this function
> + * immediately returns (successfully).
>   *
>   * Returns 0 on success, and an appropriate error value otherwise.
>   */
>  int rproc_boot(struct rproc *rproc)
>  {
> -	const struct firmware *firmware_p;
> +	const struct firmware *firmware_p = NULL;
>  	struct device *dev;
>  	int ret;
>  
> @@ -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;

Why do this on every boot? Why don't you change rproc_alloc() to never
populate rproc->firmware?

Regards,
Bjorn

>  	}
>  
>  	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
> +		 */
> +		ret = rproc_boot(rproc);
> +		if (ret < 0)
> +			return ret;
> +	} else if (rproc->auto_boot) {
> +		/* if rproc is marked always-on, request it to boot */
>  		ret = rproc_trigger_auto_boot(rproc);
>  		if (ret < 0)
>  			return ret;
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index 16ad66683ad0..4fd5bedab4fa 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -479,6 +479,7 @@ struct rproc_dump_segment {
>   * @table_sz: size of @cached_table
>   * @has_iommu: flag to indicate if remote processor is behind an MMU
>   * @auto_boot: flag to indicate if remote processor should be auto-started
> + * @skip_fw_load: remote processor has been preloaded before start sequence
>   * @dump_segments: list of segments in the firmware
>   * @nb_vdev: number of vdev currently handled by rproc
>   */
> @@ -512,6 +513,7 @@ struct rproc {
>  	size_t table_sz;
>  	bool has_iommu;
>  	bool auto_boot;
> +	bool skip_fw_load;
>  	struct list_head dump_segments;
>  	int nb_vdev;
>  };
> -- 
> 2.7.4
>