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

From: Mathieu Poirier
Date: Thu Feb 13 2020 - 15:08:20 EST

Good day,

On Tue, Feb 11, 2020 at 06:42:03PM +0100, Arnaud Pouliquen wrote:
> From: Loic Pallardy <loic.pallardy@xxxxxx>
>
> 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.
>
> Signed-off-by: Loic Pallardy <loic.pallardy@xxxxxx>
> Acked-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
> ---
> 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 097f33e4f1f3..876b5420a32b 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");
>
> /*
> * 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;

If the MCU with pre-loaded FW crashes request_firmware() in
rproc_trigger_recovery() will return an error and rproc_start()
never called.

> }
>
> 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 */

I spent way too much time staring at this modification... I can't decide if a
system where the FW has been pre-loaded should be considered "auto_boot".
Indeed the result is the same, i.e the MCU is started at boot time without user
intervention.

I'd welcome other people's opinion on this.

> 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;
> };
> --
> 2.17.1
>