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stm class: Support devices that override software assigned masters

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Some STM devices adjust software assigned master numbers depending on
the trace source and its runtime state and whatnot. This patch adds
a sysfs attribute to inform the trace-side software that master numbers
assigned to software sources will not match those in the STP stream,
so that, for example, master/channel allocation policy can be adjusted
accordingly.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexander Shishkin 2016-05-03 11:33:37 -06:00 committed by Greg Kroah-Hartman
parent 6327a454a8
commit 8e996a2874
3 changed files with 28 additions and 0 deletions
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10
Documentation/ABI/testing/sysfs-class-stm
View File

@ -12,3 +12,13 @@ KernelVersion: 4.3
Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Description:
Shows the number of channels per master on this STM device.
What: /sys/class/stm/<stm>/hw_override
Date: March 2016
KernelVersion: 4.7
Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Description:
Reads as 0 if master numbers in the STP stream produced by
this stm device will match the master numbers assigned by
the software or 1 if the stm hardware overrides software
assigned masters.

15
drivers/hwtracing/stm/core.c
View File

@ -67,9 +67,24 @@ static ssize_t channels_show(struct device *dev,
static DEVICE_ATTR_RO(channels);
static ssize_t hw_override_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct stm_device *stm = to_stm_device(dev);
int ret;
ret = sprintf(buf, "%u\n", stm->data->hw_override);
return ret;
}
static DEVICE_ATTR_RO(hw_override);
static struct attribute *stm_attrs[] = {
&dev_attr_masters.attr,
&dev_attr_channels.attr,
&dev_attr_hw_override.attr,
NULL,
};

3
include/linux/stm.h
View File

@ -50,6 +50,8 @@ struct stm_device;
* @sw_end: last STP master available to software
* @sw_nchannels: number of STP channels per master
* @sw_mmiosz: size of one channel's IO space, for mmap, optional
* @hw_override: masters in the STP stream will not match the ones
* assigned by software, but are up to the STM hardware
* @packet: callback that sends an STP packet
* @mmio_addr: mmap callback, optional
* @link: called when a new stm_source gets linked to us, optional
@ -85,6 +87,7 @@ struct stm_data {
unsigned int sw_end;
unsigned int sw_nchannels;
unsigned int sw_mmiosz;
unsigned int hw_override;
ssize_t (*packet)(struct stm_data *, unsigned int,
unsigned int, unsigned int,
unsigned int, unsigned int,