[PATCH V3 3/6] stm class: provision for statically assigned masterIDs

From: Chunyan Zhang
Date: Sat Feb 06 2016 - 06:06:32 EST


From: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>

Some architecture like ARM assign masterIDs statically at the HW design
phase, making masterID manipulation in the generic STM core irrelevant.

This patch adds a new 'mstatic' flag to struct stm_data that tells the
core that this specific STM device doesn't need explicit masterID
management. In the core sw_start/end of masterID are set to '1',
i.e there is only one masterID to deal with.

Also this patch depends on [1], so that the number of masterID
is '1' too.

Finally the lower and upper bound for masterIDs as presented
in ($SYSFS)/class/stm/XYZ.stm/masters and
($SYSFS)/../stp-policy/XYZ.stm.my_policy/some_device/masters
are set to '-1'. That way users can't confuse them with
architecture where masterID management is required (where any
other value would be valid).

[1] https://lkml.org/lkml/2015/12/22/348

Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Signed-off-by: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
---
drivers/hwtracing/stm/core.c | 18 ++++++++++++++++--
drivers/hwtracing/stm/policy.c | 18 ++++++++++++++++--
include/linux/stm.h | 8 ++++++++
3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 854a16d..d344ae7 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -44,9 +44,15 @@ static ssize_t masters_show(struct device *dev,
char *buf)
{
struct stm_device *stm = to_stm_device(dev);
- int ret;
+ int ret, sw_start, sw_end;
+
+ sw_start = stm->data->sw_start;
+ sw_end = stm->data->sw_end;

- ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);
+ if (stm->data->mstatic)
+ sw_start = sw_end = STM_STATIC_MASTERID;
+
+ ret = sprintf(buf, "%d %d\n", sw_start, sw_end);

return ret;
}
@@ -630,7 +636,15 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
if (!stm_data->packet || !stm_data->sw_nchannels)
return -EINVAL;

+ /*
+ * MasterIDs are statically set in HW. As such the core is
+ * using a single master for interaction with this device.
+ */
+ if (stm_data->mstatic)
+ stm_data->sw_start = stm_data->sw_end = 1;
+
nmasters = stm_data->sw_end - stm_data->sw_start;
+
stm = kzalloc(sizeof(*stm) + nmasters * sizeof(void *), GFP_KERNEL);
if (!stm)
return -ENOMEM;
diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
index 17a1416..c874dea 100644
--- a/drivers/hwtracing/stm/policy.c
+++ b/drivers/hwtracing/stm/policy.c
@@ -80,10 +80,17 @@ static ssize_t
stp_policy_node_masters_show(struct config_item *item, char *page)
{
struct stp_policy_node *policy_node = to_stp_policy_node(item);
+ struct stm_device *stm = policy_node->policy->stm;
+ int first_master, last_master;
ssize_t count;

- count = sprintf(page, "%u %u\n", policy_node->first_master,
- policy_node->last_master);
+ first_master = policy_node->first_master;
+ last_master = policy_node->last_master;
+
+ if (stm && stm->data->mstatic)
+ first_master = last_master = STM_STATIC_MASTERID;
+
+ count = sprintf(page, "%d %d\n", first_master, last_master);

return count;
}
@@ -106,6 +113,13 @@ stp_policy_node_masters_store(struct config_item *item, const char *page,
if (!stm)
goto unlock;

+ /*
+ * masterIDs are statically allocated in HW, no point in trying to
+ * change their values.
+ */
+ if (stm->data->mstatic)
+ goto unlock;
+
/* must be within [sw_start..sw_end], which is an inclusive range */
if (first > INT_MAX || last > INT_MAX || first > last ||
first < stm->data->sw_start ||
diff --git a/include/linux/stm.h b/include/linux/stm.h
index f351d62..c9712a7 100644
--- a/include/linux/stm.h
+++ b/include/linux/stm.h
@@ -18,6 +18,11 @@
#include <linux/device.h>

/**
+ * The masterIDs are statically set in hardware and can't be queried
+ */
+#define STM_STATIC_MASTERID -1
+
+/**
* enum stp_packet_type - STP packets that an STM driver sends
*/
enum stp_packet_type {
@@ -46,6 +51,8 @@ struct stm_device;
* struct stm_data - STM device description and callbacks
* @name: device name
* @stm: internal structure, only used by stm class code
+ * @mstatic: true if masterIDs are assigned in HW. If so @sw_start
+ * and @sw_end are set to '1' by the core.
* @sw_start: first STP master available to software
* @sw_end: last STP master available to software
* @sw_nchannels: number of STP channels per master
@@ -71,6 +78,7 @@ struct stm_device;
struct stm_data {
const char *name;
struct stm_device *stm;
+ bool mstatic;
unsigned int sw_start;
unsigned int sw_end;
unsigned int sw_nchannels;
--
1.9.1