Messages in this thread | | | From | Andy Shevchenko <> | Date | Tue, 5 May 2020 16:49:50 +0300 | Subject | Re: [PATCH 3/3] platform/x86: Intel PMT Telemetry capability driver |
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On Tue, May 5, 2020 at 5:32 AM David E. Box <david.e.box@linux.intel.com> wrote:
...
> Register mappings are not provided by the driver. Instead, a GUID is read > from a header for each endpoint. The GUID identifies the device and is to > be used with an XML, provided by the vendor, to discover the available set > of metrics and their register mapping. This allows firmware updates to > modify the register space without needing to update the driver every time > with new mappings. Firmware writes a new GUID in this case to specify the > new mapping. Software tools with access to the associated XML file can > then interpret the changes.
Is old hardware going to support this in the future? (I have in mind Apollo Lake / Broxton)
> This module manages access to all PMT Telemetry endpoints on a system, > regardless of the device exporting them. It creates an intel_pmt_telem
Name is not the best we can come up with. Would anyone else use PMT? Would it be vendor-agnostic ABI? (For example, I know that MIPI standardizes tracing protocols, like STM, do we have any plans to standardize this one?)
telem -> telemetry.
> class to manage the list. For each endpoint, sysfs files provide GUID and > size information as well as a pointer to the parent device the telemetry > comes from. Software may discover the association between endpoints and > devices by iterating through the list in sysfs, or by looking for the > existence of the class folder under the device of interest. A device node > of the same name allows software to then map the telemetry space for direct > access.
...
> + tristate "Intel PMT telemetry driver"
I think user should understand what is it from the title (hint: spell PMT fully).
...
> obj-$(CONFIG_PMC_ATOM) += pmc_atom.o > +obj-$(CONFIG_INTEL_PMT_TELEM) += intel_pmt_telem.o
Keep this and Kconfig section in order with the other stuff.
...
bits.h?
> +#include <linux/cdev.h> > +#include <linux/intel-dvsec.h> > +#include <linux/io-64-nonatomic-lo-hi.h> > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/pci.h> > +#include <linux/platform_device.h> > +#include <linux/slab.h> > +#include <linux/uaccess.h> > +#include <linux/xarray.h>
...
> +/* platform device name to bind to driver */ > +#define TELEM_DRV_NAME "pmt_telemetry"
Shouldn't be part of MFD header?
...
> +#define TELEM_TBIR_MASK 0x7
GENMASK() ?
> +struct pmt_telem_priv { > + struct device *dev; > + struct intel_dvsec_header *dvsec; > + struct telem_header header; > + unsigned long base_addr; > + void __iomem *disc_table; > + struct cdev cdev; > + dev_t devt; > + int devid; > +};
...
> + unsigned long phys = priv->base_addr; > + unsigned long pfn = PFN_DOWN(phys); > + unsigned long psize; > + > + psize = (PFN_UP(priv->base_addr + priv->header.size) - pfn) * PAGE_SIZE; > + if (vsize > psize) { > + dev_err(priv->dev, "Requested mmap size is too large\n"); > + return -EINVAL; > + }
...
> +static ssize_t guid_show(struct device *dev, struct device_attribute *attr, > + char *buf) > +{ > + struct pmt_telem_priv *priv = dev_get_drvdata(dev); > + > + return sprintf(buf, "0x%x\n", priv->header.guid); > +}
So, it's not a GUID but rather some custom number? Can we actually do a real GUID / UUID here? Because of TODO below I suppose it's not carved in stone (yet) and basically a protocol defined by firmware (which can be amended).
...
> + /* TODO: replace with device properties??? */
So, please, fulfill. swnode I guess is what you are looking for.
> + priv->dvsec = dev_get_platdata(&pdev->dev); > + if (!priv->dvsec) { > + dev_err(&pdev->dev, "Platform data not found\n"); > + return -ENODEV; > + }
...
> + /* Local access and BARID only for now */ > + switch (priv->header.access_type) { > + case TELEM_ACCESS_LOCAL: > + if (priv->header.tbir) { > + dev_err(&pdev->dev, > + "Unsupported BAR index %d for access type %d\n", > + priv->header.tbir, priv->header.access_type); > + return -EINVAL; > + }
> + fallthrough;
What's the point?
> + > + case TELEM_ACCESS_BARID: > + break; > + default: > + dev_err(&pdev->dev, "Unsupported access type %d\n", > + priv->header.access_type); > + return -EINVAL; > + }
> + err = alloc_chrdev_region(&priv->devt, 0, 1, TELEM_DRV_NAME);
err or ret? Be consistent in the module.
> + if (err < 0) {
' < 0' Do we need it?
> + dev_err(&pdev->dev, > + "PMT telemetry chrdev_region err: %d\n", err); > + return err; > + }
...
> + err = pmt_telem_create_dev(priv); > + if (err < 0)
' < 0' Do we need it?
> + goto fail_create_dev; > + > + return 0;
> +}
...
> +static const struct platform_device_id pmt_telem_table[] = { > + { > + .name = "pmt_telemetry", > + }, { > + /* sentinel */ > + }
{ .name = ... }, {}
is enough.
> +};
...
> +static int __init pmt_telem_init(void) > +{
> + int ret = class_register(&pmt_telem_class); > + > + if (ret)
int ret;
ret = ... if (ret)
> + return ret; > + > + ret = platform_driver_register(&pmt_telem_driver); > + if (ret) > + class_unregister(&pmt_telem_class); > + > + return ret; > +}
...
> +{
> +}
> +
Extra blank line.
> +module_init(pmt_telem_init); > +module_exit(pmt_telem_exit);
Better to attach to the respective functions.
...
> +#include <linux/intel-dvsec.h>
There is no user of this below, but types.h has users here.
> +/* Telemetry types */ > +#define PMT_TELEM_TELEMETRY 0 > +#define PMT_TELEM_CRASHLOG 1 > + > +struct telem_header {
> + u8 access_type;
If it's part of hardware communication, shouldn't be rather __uXX types to show that this is part of protocol between software and hardware?
> + u8 telem_type; > + u16 size; > + u32 guid; > + u32 base_offset; > + u8 tbir; > +};
-- With Best Regards, Andy Shevchenko
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