Re: [RFC PATCH 1/1] soc: qcom: Add driver to read secondary bootloader (XBL) log

[Ninad Naik]

Hi Pavan,

On 8/22/2023 6:09 PM, Pavan Kondeti wrote:
> On Tue, Aug 22, 2023 at 05:45:12PM +0530, Ninad Naik wrote:
> > Qualcomm secondary bootloader (XBL) boot log holds information to
> > identify various firmware configuration currently set on the SoC.
> > The XBL log is stored in a predefined reserved memory region.
> >
> > This drivers provides a way to print XBL logs on the console. To
> > do so, it provides a debugfs entry which captures the logs stored
> > in this reserved memory region. This entry can now be used to read
> > and print the XBL logs to console.
> >
> > User can use the below command to print XBL log to console:
> >          cat /sys/kernel/debug/xbl_log
> >
> > Signed-off-by: Ninad Naik <quic_ninanaik@xxxxxxxxxxx>
> > ---
>
> For a single patch, cover letter may not be needed. The under cut
> portion (this area) of the patch can be used to present the additional
> details.
Ack.
> >   drivers/soc/qcom/Kconfig        |  13 +++
> >   drivers/soc/qcom/Makefile       |   1 +
> >   drivers/soc/qcom/dump_xbl_log.c | 139 ++++++++++++++++++++++++++++++++
> >   3 files changed, 153 insertions(+)
> >   create mode 100644 drivers/soc/qcom/dump_xbl_log.c
>
> [...]
>
> > +static int map_addr_range(struct device_node **parent, const char *name,
> > +			  struct xbl_log_data *xbl_data)
> > +{
> > +	struct device_node *node;
> > +	struct resource res;
> > +	int ret;
> > +
> > +	node = of_find_node_by_name(*parent, name);
> > +	if (!node)
> > +		return -ENODEV;
> > +
> > +	ret = of_address_to_resource(node, 0, &res);
> > +	if (ret) {
> > +		dev_err(xbl_data->dev, "Failed to parse memory region\n");
> > +		return ret;
> > +	}
> > +	of_node_put(node);
> > +
> > +	if (!resource_size(&res)) {
> > +		dev_err(xbl_data->dev, "Failed to parse memory region size\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	xbl_data->buf_size = resource_size(&res) - 1;
> > +	xbl_data->xbl_buf = devm_memremap(xbl_data->dev, res.start,
> > +					  xbl_data->buf_size, MEMREMAP_WB);
> > +	if (!xbl_data->xbl_buf) {
> > +		dev_err(xbl_data->dev, "%s: memory remap failed\n", name);
> > +		return -ENOMEM;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int xbl_log_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct xbl_log_data *xbl_data;
> > +	struct device_node *parent;
> > +	int ret;
> > +
> > +	xbl_data = devm_kzalloc(dev, sizeof(*xbl_data), GFP_KERNEL);
> > +	if (!xbl_data)
> > +		return -ENOMEM;
> > +
> > +	xbl_data->dev = &pdev->dev;
> > +	platform_set_drvdata(pdev, xbl_data);
> > +
> > +	parent = of_find_node_by_path("/reserved-memory");
> > +	if (!parent) {
> > +		dev_err(xbl_data->dev, "reserved-memory node missing\n");
> > +		return -ENODEV;
> > +	}
> > +
>
> You would need to present the Device Tree binding document for this. For
> ex: pls see
> Documentation/devicetree/bindings/reserved-memory/qcom,cmd-db.yaml
Ack. Will add a corresponding DT binding in the next version
> > +	ret = map_addr_range(&parent, "uefi-log", xbl_data);
> > +	if (ret)
> > +		goto put_node;
> > +
> > +	xbl_data->dbg_data.data = xbl_data->xbl_buf;
> > +	xbl_data->dbg_data.size = xbl_data->buf_size;
> > +	xbl_data->dbg_file = debugfs_create_blob("xbl_log", 0400, NULL,
> > +						 &xbl_data->dbg_data);
> > +	if (IS_ERR(xbl_data->dbg_file)) {
> > +		dev_err(xbl_data->dev, "failed to create debugfs entry\n");
> > +		ret = PTR_ERR(xbl_data->dbg_file);
> > +	}
> > +
> > +put_node:
> > +	of_node_put(parent);
> > +	return ret;
> > +}
> > +
> > +static int xbl_log_remove(struct platform_device *pdev)
> > +{
> > +	struct xbl_log_data *xbl_data = platform_get_drvdata(pdev);
> > +
> > +	debugfs_remove_recursive(xbl_data->dbg_file);
> > +	return 0;
> > +}
> > +
> > +static struct platform_driver xbl_log_driver = {
> > +	.probe = xbl_log_probe,
> > +	.remove = xbl_log_remove,
> > +	.driver = {
> > +		   .name = "xbl-log",
> > +		   },
> > +};
> > +
> > +static struct platform_device xbl_log_device = {
> > +	.name = "xbl-log",
> > +};
> > +
> > +static int __init xbl_log_init(void)
> > +{
> > +	int ret = 0;
> > +
> > +	ret = platform_driver_register(&xbl_log_driver);
> > +	if (!ret) {
> > +		ret = platform_device_register(&xbl_log_device);
> > +		if (ret)
> > +			platform_driver_unregister(&xbl_log_driver);
> > +	}
> > +	return ret;
> > +}
> > +
>
> The platform device registration, the resource parsing can be completely
> avoided by adding your compatible entry to reserved_mem_matches
> structure defined in drivers/of/platform.c . There are some Qualcomm SoC
> devices also present in that list.
Ack. So once the compatible entry is added to reserved_mem_matches 
structure here, a platform_device is created for this node to which this 
driver can bind to. Thank you for the suggestion, I'll make the 
necessary corrections in the next revision.

> > +static void __exit xbl_log_exit(void)
> > +{
> > +	platform_device_unregister(&xbl_log_device);
> > +	platform_driver_unregister(&xbl_log_driver);
> > +}
> > +
> > +module_init(xbl_log_init);
> > +module_exit(xbl_log_exit);
> > +
> > +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. (QTI) XBL log driver");
> > +MODULE_LICENSE("GPL");
> > --
> > 2.41.0
Thanks,
Ninad