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

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Date:   Tue, 22 Aug 2023 18:09:33 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Ninad Naik <quic_ninanaik@...cinc.com>
CC:     <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <psodagud@...cinc.com>,
        <quic_ppareek@...cinc.com>, <quic_kprasan@...cinc.com>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <kernel@...cinc.com>
Subject: Re: [RFC PATCH 1/1] soc: qcom: Add driver to read secondary
 bootloader (XBL) log

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@...cinc.com>
> ---

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.

>  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 

> +	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.

> +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
>