Re: [PATCH V4 2/3] mfd: Intel Platform Monitoring Technology support

[Lee Jones]

On Fri, 17 Jul 2020, David E. Box wrote:

> Intel Platform Monitoring Technology (PMT) is an architecture for
> enumerating and accessing hardware monitoring facilities. PMT supports
> multiple types of monitoring capabilities. This driver creates platform
> devices for each type so that they may be managed by capability specific
> drivers (to be introduced). Capabilities are discovered using PCIe DVSEC
> ids. Support is included for the 3 current capability types, Telemetry,
> Watcher, and Crashlog. The features are available on new Intel platforms
> starting from Tiger Lake for which support is added.
> 
> Also add a quirk mechanism for several early hardware differences and bugs.
> For Tiger Lake, do not support Watcher and Crashlog capabilities since they
> will not be compatible with future product. Also, fix use a quirk to fix
> the discovery table offset.
> 
> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Co-developed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx>

This should be in chronological order.

> ---
>  MAINTAINERS             |   5 +
>  drivers/mfd/Kconfig     |  10 ++
>  drivers/mfd/Makefile    |   1 +
>  drivers/mfd/intel_pmt.c | 215 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 231 insertions(+)
>  create mode 100644 drivers/mfd/intel_pmt.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index b4a43a9e7fbc..2e42bf0c41ab 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8845,6 +8845,11 @@ F:	drivers/mfd/intel_soc_pmic*
>  F:	include/linux/mfd/intel_msic.h
>  F:	include/linux/mfd/intel_soc_pmic*
>  
> +INTEL PMT DRIVER
> +M:	"David E. Box" <david.e.box@xxxxxxxxxxxxxxx>
> +S:	Maintained
> +F:	drivers/mfd/intel_pmt.c
> +
>  INTEL PRO/WIRELESS 2100, 2200BG, 2915ABG NETWORK CONNECTION SUPPORT
>  M:	Stanislav Yakovlev <stas.yakovlev@xxxxxxxxx>
>  L:	linux-wireless@xxxxxxxxxxxxxxx
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index a37d7d171382..1a62ce2c68d9 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -670,6 +670,16 @@ config MFD_INTEL_PMC_BXT
>  	  Register and P-unit access. In addition this creates devices
>  	  for iTCO watchdog and telemetry that are part of the PMC.
>  
> +config MFD_INTEL_PMT
> +	tristate "Intel Platform Monitoring Technology support"

Nit: "Intel Platform Monitoring Technology (PMT) support"

> +	depends on PCI
> +	select MFD_CORE
> +	help
> +	  The Intel Platform Monitoring Technology (PMT) is an interface that
> +	  provides access to hardware monitor registers. This driver supports
> +	  Telemetry, Watcher, and Crashlog PMT capabilities/devices for
> +	  platforms starting from Tiger Lake.
> +
>  config MFD_IPAQ_MICRO
>  	bool "Atmel Micro ASIC (iPAQ h3100/h3600/h3700) Support"
>  	depends on SA1100_H3100 || SA1100_H3600
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 9367a92f795a..1961b4737985 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -216,6 +216,7 @@ obj-$(CONFIG_MFD_INTEL_LPSS_PCI)	+= intel-lpss-pci.o
>  obj-$(CONFIG_MFD_INTEL_LPSS_ACPI)	+= intel-lpss-acpi.o
>  obj-$(CONFIG_MFD_INTEL_MSIC)	+= intel_msic.o
>  obj-$(CONFIG_MFD_INTEL_PMC_BXT)	+= intel_pmc_bxt.o
> +obj-$(CONFIG_MFD_INTEL_PMT)	+= intel_pmt.o
>  obj-$(CONFIG_MFD_PALMAS)	+= palmas.o
>  obj-$(CONFIG_MFD_VIPERBOARD)    += viperboard.o
>  obj-$(CONFIG_MFD_RC5T583)	+= rc5t583.o rc5t583-irq.o
> diff --git a/drivers/mfd/intel_pmt.c b/drivers/mfd/intel_pmt.c
> new file mode 100644
> index 000000000000..6857eaf4ff86
> --- /dev/null
> +++ b/drivers/mfd/intel_pmt.c
> @@ -0,0 +1,215 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Intel Platform Monitoring Technology MFD driver

s/MFD/(PMT)/

> + * Copyright (c) 2020, Intel Corporation.
> + * All Rights Reserved.
> + *
> + * Authors: David E. Box <david.e.box@xxxxxxxxxxxxxxx>

Looks odd to use a plural for a single author.

> + */
> +
> +#include <linux/bits.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/mfd/core.h>
> +#include <linux/types.h>

Alphabetical please.

> +/* Intel DVSEC capability vendor space offsets */
> +#define INTEL_DVSEC_ENTRIES		0xA
> +#define INTEL_DVSEC_SIZE		0xB
> +#define INTEL_DVSEC_TABLE		0xC
> +#define INTEL_DVSEC_TABLE_BAR(x)	((x) & GENMASK(2, 0))
> +#define INTEL_DVSEC_TABLE_OFFSET(x)	((x) & GENMASK(31, 3))
> +#define INTEL_DVSEC_ENTRY_SIZE		4
> +
> +/* PMT capabilities */
> +#define DVSEC_INTEL_ID_TELEMETRY	2
> +#define DVSEC_INTEL_ID_WATCHER		3
> +#define DVSEC_INTEL_ID_CRASHLOG		4
> +
> +#define TELEMETRY_DEV_NAME		"pmt_telemetry"
> +#define WATCHER_DEV_NAME		"pmt_watcher"
> +#define CRASHLOG_DEV_NAME		"pmt_crashlog"

Please don't define names of things.  It makes grepping a pain, at the
very least.  Just use the 'raw' string in-place.

> +struct intel_dvsec_header {
> +	u16	length;
> +	u16	id;
> +	u8	num_entries;
> +	u8	entry_size;
> +	u8	tbir;
> +	u32	offset;
> +};
> +
> +enum pmt_quirks {
> +	/* Watcher capability not supported */
> +	PMT_QUIRK_NO_WATCHER	= BIT(0),
> +
> +	/* Crashlog capability not supported */
> +	PMT_QUIRK_NO_CRASHLOG	= BIT(1),
> +
> +	/* Use shift instead of mask to read discovery table offset */
> +	PMT_QUIRK_TABLE_SHIFT	= BIT(2),
> +};
> +
> +struct pmt_platform_info {
> +	unsigned long quirks;
> +};
> +
> +static const struct pmt_platform_info tgl_info = {
> +	.quirks = PMT_QUIRK_NO_WATCHER | PMT_QUIRK_NO_CRASHLOG |
> +		  PMT_QUIRK_TABLE_SHIFT,
> +};
> +
> +static int
> +pmt_add_dev(struct pci_dev *pdev, struct intel_dvsec_header *header,
> +	    struct pmt_platform_info *info)

My personal preference is to a) only break when you have to and b) to
align with the '('.  Perhaps point b) is satisfied and it's just the
patch format that's shifting the tab though?

> +{
> +	struct device *dev = &pdev->dev;
> +	struct resource *res, *tmp;
> +	struct mfd_cell *cell;
> +	const char *name;
> +	int count = header->num_entries;
> +	int size = header->entry_size;
> +	int i;
> +
> +	switch (header->id) {
> +	case DVSEC_INTEL_ID_TELEMETRY:
> +		name = TELEMETRY_DEV_NAME;
> +		break;
> +	case DVSEC_INTEL_ID_WATCHER:
> +		if (info->quirks & PMT_QUIRK_NO_WATCHER) {
> +			dev_info(dev, "Watcher not supported\n");
> +			return 0;
> +		}
> +		name = WATCHER_DEV_NAME;
> +		break;
> +	case DVSEC_INTEL_ID_CRASHLOG:
> +		if (info->quirks & PMT_QUIRK_NO_CRASHLOG) {
> +			dev_info(dev, "Crashlog not supported\n");
> +			return 0;
> +		}
> +		name = CRASHLOG_DEV_NAME;
> +		break;
> +	default:
> +		return -EINVAL;

Doesn't deserve an error message?

> +	}
> +
> +	if (!header->num_entries || !header->entry_size) {
> +		dev_warn(dev, "Invalid count or size for %s header\n", name);
> +		return -EINVAL;

If you're returning an error, this should be dev_err().

Even if you only handle it as a warning at the call site.

> +	}
> +
> +	cell = devm_kzalloc(dev, sizeof(*cell), GFP_KERNEL);
> +	if (!cell)
> +		return -ENOMEM;
> +
> +	res = devm_kcalloc(dev, count, sizeof(*res), GFP_KERNEL);
> +	if (!res)
> +		return -ENOMEM;
> +
> +	if (info->quirks & PMT_QUIRK_TABLE_SHIFT)
> +		header->offset >>= 3;
> +
> +	for (i = 0, tmp = res; i < count; i++, tmp++) {
> +		tmp->start = pdev->resource[header->tbir].start +
> +			     header->offset + i * (size << 2);

Deserves a comment I think.

> +		tmp->end = tmp->start + (size << 2) - 1;
> +		tmp->flags = IORESOURCE_MEM;
> +	}
> +
> +	cell->resources = res;
> +	cell->num_resources = count;
> +	cell->name = name;
> +
> +	return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO, cell, 1, NULL, 0,
> +				    NULL);
> +}
> +
> +static int
> +pmt_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> +{
> +	struct intel_dvsec_header header;
> +	struct pmt_platform_info *info;
> +	bool found_devices = false;
> +	int ret, pos = 0;
> +	u32 table;
> +	u16 vid;
> +
> +	ret = pcim_enable_device(pdev);
> +	if (ret)
> +		return ret;
> +
> +	info = devm_kmemdup(&pdev->dev, (void *)id->driver_data, sizeof(*info),
> +			    GFP_KERNEL);
> +	if (!info)
> +		return -ENOMEM;
> +
> +	pos = pci_find_next_ext_capability(pdev, pos, PCI_EXT_CAP_ID_DVSEC);
> +	while (pos) {

If you do:

	do {
		int pos;

		pos = pci_find_next_ext_capability(pdev, pos, PCI_EXT_CAP_ID_DVSEC);
		if (!pos)
			break;

Then you can invoke pci_find_next_ext_capability() once, no?

> +		pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER1, &vid);
> +		if (vid != PCI_VENDOR_ID_INTEL)
> +			continue;
> +
> +		pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER2,
> +				     &header.id);
> +		pci_read_config_byte(pdev, pos + INTEL_DVSEC_ENTRIES,
> +				     &header.num_entries);
> +		pci_read_config_byte(pdev, pos + INTEL_DVSEC_SIZE,
> +				     &header.entry_size);
> +		pci_read_config_dword(pdev, pos + INTEL_DVSEC_TABLE,
> +				      &table);
> +
> +		header.tbir = INTEL_DVSEC_TABLE_BAR(table);
> +		header.offset = INTEL_DVSEC_TABLE_OFFSET(table);
> +
> +		ret = pmt_add_dev(pdev, &header, info);
> +		if (ret)
> +			dev_warn(&pdev->dev,
> +				 "Failed to add devices for DVSEC id %d\n",

"device", so not all devices, right?

> +				 header.id);

Don't you want to continue here?

Else you're going to set found_devices for a failed device.

> +		found_devices = true;
> +
> +		pos = pci_find_next_ext_capability(pdev, pos,
> +						   PCI_EXT_CAP_ID_DVSEC);
> +	}
> +
> +	if (!found_devices) {
> +		dev_err(&pdev->dev, "No supported PMT capabilities found.\n");
> +		return -ENODEV;
> +	}
> +
> +	pm_runtime_put(&pdev->dev);
> +	pm_runtime_allow(&pdev->dev);
> +
> +	return 0;
> +}
> +
> +static void pmt_pci_remove(struct pci_dev *pdev)
> +{
> +	pm_runtime_forbid(&pdev->dev);
> +	pm_runtime_get_sync(&pdev->dev);
> +}
> +
> +#define PCI_DEVICE_ID_INTEL_PMT_TGL	0x9a0d

What's this for?

If this is PCI_DEVICE_DATA magic, it would be worth tying it to the
struct i.e. remove the empty line between it and the table below.

> +static const struct pci_device_id pmt_pci_ids[] = {
> +	{ PCI_DEVICE_DATA(INTEL, PMT_TGL, &tgl_info) },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(pci, pmt_pci_ids);
> +
> +static struct pci_driver pmt_pci_driver = {
> +	.name = "intel-pmt",
> +	.id_table = pmt_pci_ids,
> +	.probe = pmt_pci_probe,
> +	.remove = pmt_pci_remove,
> +};
> +module_pci_driver(pmt_pci_driver);
> +
> +MODULE_AUTHOR("David E. Box <david.e.box@xxxxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Intel Platform Monitoring Technology MFD driver");

s/MFD/(PMT)/

> +MODULE_LICENSE("GPL v2");

-- 
Lee Jones [æçæ]
Senior Technical Lead - Developer Services
Linaro.org â Open source software for Arm SoCs
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