Re: [PATCH v1] ASoC: tas2783-sdw: Add basic BPT support

[Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>]

> +static int tas2783_fw_download_bpt(struct tas2783_prv *tas_dev,
> +				   const struct firmware *fmw)
> +{
> +	struct sdw_slave *slave = tas_dev->sdw_peripheral;
> +	struct sdw_bpt_section *sections = NULL;
> +	struct sdw_bus *bus = slave->bus;
> +	struct sdw_bpt_msg msg = {0};
> +	struct tas_fw_file file;
> +	struct tas_fw_hdr hdr;
> +	size_t offset = FW_DL_OFFSET;
> +	size_t img_sz = fmw->size;
> +	const u8 *buf = fmw->data;
> +	int num_sections = 0;
> +	int i, ret;
> +
> +	if (img_sz < FW_DL_OFFSET)
> +		return -EINVAL;
> +
> +	tas_fw_read_hdr(buf, &hdr);
> +	if (hdr.size != img_sz)
> +		return -EINVAL;
> +
> +	while (offset < (img_sz - FW_FL_HDR)) {
> +		size_t adv = (size_t)tas_fw_get_next_file(&buf[offset], &file);
> +
> +		/*
> +		 * Reject a section whose payload runs past the image. Compare
> +		 * file.length (not adv) against the space left after this
> +		 * section's header, so the check is immune to the size_t wrap
> +		 * in tas_fw_get_next_file() on 32-bit kernels.
> +		 */
> +		if (file.length > img_sz - offset - FW_FL_HDR) {
> +			dev_err(tas_dev->dev,
> +				"Firmware section at offset %zu exceeded.\n",
> +				offset);
> +			return -EINVAL;
> +		}
> +		if (num_sections >= TAS2783_MAX_FW_SECTIONS) {
> +			dev_err(tas_dev->dev,
> +				"BPT fw has too many sections (max %d)\n",
> +				TAS2783_MAX_FW_SECTIONS);
> +			return -EINVAL;
> +		}
> +		offset += adv;
> +		num_sections++;
> +	}
> +
> +	if (num_sections == 0)
> +		return -EINVAL;
> +
> +	sections = kcalloc(num_sections, sizeof(*sections), GFP_KERNEL);
> +	if (!sections)
> +		return -ENOMEM;
> +
> +	offset = FW_DL_OFFSET;
> +	for (i = 0; i < num_sections && offset < (img_sz - FW_FL_HDR); i++) {
> +		size_t adv = (size_t)tas_fw_get_next_file(&buf[offset], &file);
> +
> +		sections[i].addr = file.dest_addr;
> +		sections[i].len = file.length;
> +		sections[i].buf = file.fw_data;
> +		offset += adv;
> +
> +		dev_dbg(tas_dev->dev, "BPT section %d: addr=0x%x len=%d",
> +			i, file.dest_addr, file.length);
> +	}
> +
> +	msg.sec = sections;
> +	msg.sections = num_sections;
> +	msg.dev_num = slave->dev_num;
> +	msg.flags = SDW_MSG_FLAG_WRITE;
> +
> +	dev_dbg(tas_dev->dev, "BPT starting: %d sections, dev_num=%d",
> +		num_sections, slave->dev_num);
> +
> +	ret = sdw_bpt_send_sync(bus, slave, &msg);
> +
> +	if (ret < 0)
> +		dev_err(tas_dev->dev, "BPT firmware download failed: %d", ret);
> +	else
> +		dev_dbg(tas_dev->dev,
> +			 "BPT firmware download complete: %d sections",
> +			 num_sections);
> +
> +	kfree(sections);
> +	return ret;
> +}
Before adding BPT-based optimizations to speed-up firmware download,
it'd be good to address existing problems with firmware download, e.g.
when a firmware contains volume configuration information that bypasses
regmap, see the thread in "ASoC: tas2783-sdw: keep the volume settings
across resets". Using BPT will only make things worse I am afraid,
unless there's a check that this is only used for resources not managed
by regmap?