docs: riscv: convert docs to ReST and rename to *.rst
The conversion here is trivial:
- Adjust the document title's markup
- Do some whitespace alignment;
- mark literal blocks;
- Use ReST way to markup indented lists.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/riscv/index.rst b/Documentation/riscv/index.rst
new file mode 100644
index 0000000..c4b906d
--- /dev/null
+++ b/Documentation/riscv/index.rst
@@ -0,0 +1,17 @@
+:orphan:
+
+===================
+RISC-V architecture
+===================
+
+.. toctree::
+ :maxdepth: 1
+
+ pmu
+
+.. only:: subproject and html
+
+ Indices
+ =======
+
+ * :ref:`genindex`
diff --git a/Documentation/riscv/pmu.txt b/Documentation/riscv/pmu.rst
similarity index 77%
rename from Documentation/riscv/pmu.txt
rename to Documentation/riscv/pmu.rst
index b29f03a..acb216b 100644
--- a/Documentation/riscv/pmu.txt
+++ b/Documentation/riscv/pmu.rst
@@ -1,5 +1,7 @@
+===================================
Supporting PMUs on RISC-V platforms
-==========================================
+===================================
+
Alan Kao <alankao@andestech.com>, Mar 2018
Introduction
@@ -77,13 +79,13 @@
(2) privilege level setting (user space only, kernel space only, both);
(3) destructor setting. Normally it is sufficient to apply *riscv_destroy_event*;
(4) tweaks for non-sampling events, which will be utilized by functions such as
-*perf_adjust_period*, usually something like the follows:
+ *perf_adjust_period*, usually something like the follows::
-if (!is_sampling_event(event)) {
- hwc->sample_period = x86_pmu.max_period;
- hwc->last_period = hwc->sample_period;
- local64_set(&hwc->period_left, hwc->sample_period);
-}
+ if (!is_sampling_event(event)) {
+ hwc->sample_period = x86_pmu.max_period;
+ hwc->last_period = hwc->sample_period;
+ local64_set(&hwc->period_left, hwc->sample_period);
+ }
In the case of *riscv_base_pmu*, only (3) is provided for now.
@@ -94,10 +96,10 @@
3.1. Interrupt Initialization
This often occurs at the beginning of the *event_init* method. In common
-practice, this should be a code segment like
+practice, this should be a code segment like::
-int x86_reserve_hardware(void)
-{
+ int x86_reserve_hardware(void)
+ {
int err = 0;
if (!atomic_inc_not_zero(&pmc_refcount)) {
@@ -114,7 +116,7 @@
}
return err;
-}
+ }
And the magic is in *reserve_pmc_hardware*, which usually does atomic
operations to make implemented IRQ accessible from some global function pointer.
@@ -128,28 +130,28 @@
3.2. IRQ Structure
-Basically, a IRQ runs the following pseudo code:
+Basically, a IRQ runs the following pseudo code::
-for each hardware counter that triggered this overflow
+ for each hardware counter that triggered this overflow
- get the event of this counter
+ get the event of this counter
- // following two steps are defined as *read()*,
- // check the section Reading/Writing Counters for details.
- count the delta value since previous interrupt
- update the event->count (# event occurs) by adding delta, and
- event->hw.period_left by subtracting delta
+ // following two steps are defined as *read()*,
+ // check the section Reading/Writing Counters for details.
+ count the delta value since previous interrupt
+ update the event->count (# event occurs) by adding delta, and
+ event->hw.period_left by subtracting delta
- if the event overflows
- sample data
- set the counter appropriately for the next overflow
+ if the event overflows
+ sample data
+ set the counter appropriately for the next overflow
- if the event overflows again
- too frequently, throttle this event
- fi
- fi
+ if the event overflows again
+ too frequently, throttle this event
+ fi
+ fi
-end for
+ end for
However as of this writing, none of the RISC-V implementations have designed an
interrupt for perf, so the details are to be completed in the future.
@@ -195,23 +197,26 @@
At this stage, a general event is bound to a physical counter, if any.
The state changes to PERF_HES_STOPPED and PERF_HES_UPTODATE, because it is now
stopped, and the (software) event count does not need updating.
-** *start* is then called, and the counter is enabled.
- With flag PERF_EF_RELOAD, it writes an appropriate value to the counter (check
- previous section for detail).
- Nothing is written if the flag does not contain PERF_EF_RELOAD.
- The state now is reset to none, because it is neither stopped nor updated
- (the counting already started)
+
+ - *start* is then called, and the counter is enabled.
+ With flag PERF_EF_RELOAD, it writes an appropriate value to the counter (check
+ previous section for detail).
+ Nothing is written if the flag does not contain PERF_EF_RELOAD.
+ The state now is reset to none, because it is neither stopped nor updated
+ (the counting already started)
+
* When being context-switched out, *del* is called. It then checks out all the
events in the PMU and calls *stop* to update their counts.
-** *stop* is called by *del*
- and the perf core with flag PERF_EF_UPDATE, and it often shares the same
- subroutine as *read* with the same logic.
- The state changes to PERF_HES_STOPPED and PERF_HES_UPTODATE, again.
-** Life cycle of these two pairs: *add* and *del* are called repeatedly as
- tasks switch in-and-out; *start* and *stop* is also called when the perf core
- needs a quick stop-and-start, for instance, when the interrupt period is being
- adjusted.
+ - *stop* is called by *del*
+ and the perf core with flag PERF_EF_UPDATE, and it often shares the same
+ subroutine as *read* with the same logic.
+ The state changes to PERF_HES_STOPPED and PERF_HES_UPTODATE, again.
+
+ - Life cycle of these two pairs: *add* and *del* are called repeatedly as
+ tasks switch in-and-out; *start* and *stop* is also called when the perf core
+ needs a quick stop-and-start, for instance, when the interrupt period is being
+ adjusted.
Current implementation is sufficient for now and can be easily extended to
features in the future.
@@ -225,25 +230,26 @@
Both structures are designed to be read-only.
*struct pmu* defines some function pointer interfaces, and most of them take
-*struct perf_event* as a main argument, dealing with perf events according to
-perf's internal state machine (check kernel/events/core.c for details).
+ *struct perf_event* as a main argument, dealing with perf events according to
+ perf's internal state machine (check kernel/events/core.c for details).
*struct riscv_pmu* defines PMU-specific parameters. The naming follows the
-convention of all other architectures.
+ convention of all other architectures.
* struct perf_event: include/linux/perf_event.h
* struct hw_perf_event
The generic structure that represents perf events, and the hardware-related
-details.
+ details.
* struct riscv_hw_events: arch/riscv/include/asm/perf_event.h
The structure that holds the status of events, has two fixed members:
-the number of events and the array of the events.
+ the number of events and the array of the events.
References
----------
[1] https://github.com/riscv/riscv-linux/pull/124
+
[2] https://groups.google.com/a/groups.riscv.org/forum/#!topic/sw-dev/f19TmCNP6yA
