[PATCH 08/17] coresight: tmc: Add configuration support for trace buffer size

[Suzuki K Poulose]

Now that we can dynamically switch between contiguous memory and
SG table depending on the trace buffer size, provide the support
for selecting an appropriate buffer size.

Cc: Mathieu Poirier <mathieu.poir...@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com>
---
 .../ABI/testing/sysfs-bus-coresight-devices-tmc    |  8 ++++++
 drivers/hwtracing/coresight/coresight-tmc.c        | 32 ++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc 
b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc
index 4fe677ed1305..3675c380caf8 100644
--- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc
@@ -83,3 +83,11 @@ KernelVersion:       4.7
 Contact:       Mathieu Poirier <mathieu.poir...@linaro.org>
 Description:   (R) Indicates the capabilities of the Coresight TMC.
                The value is read directly from the DEVID register, 0xFC8,
+
+What:          /sys/bus/coresight/devices/<memory_map>.tmc/buffer-size
+Date:          September 2017
+KernelVersion: 4.15
+Contact:       Mathieu Poirier <mathieu.poir...@linaro.org>
+Description:   (RW) Size of the trace buffer for TMC-ETR when used in SYSFS
+               mode. Writable only for TMC-ETR configurations. The value
+               should be aligned to the kernel pagesize.
diff --git a/drivers/hwtracing/coresight/coresight-tmc.c 
b/drivers/hwtracing/coresight/coresight-tmc.c
index c7201e40d737..2349b1805694 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -283,8 +283,40 @@ static ssize_t trigger_cntr_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(trigger_cntr);
 
+static ssize_t buffer_size_show(struct device *dev,
+                               struct device_attribute *attr, char *buf)
+{
+       struct tmc_drvdata *drvdata = dev_get_drvdata(dev->parent);
+
+       return sprintf(buf, "%#x\n", drvdata->size);
+}
+
+static ssize_t buffer_size_store(struct device *dev,
+                            struct device_attribute *attr,
+                            const char *buf, size_t size)
+{
+       int ret;
+       unsigned long val;
+       struct tmc_drvdata *drvdata = dev_get_drvdata(dev->parent);
+
+       if (drvdata->config_type != TMC_CONFIG_TYPE_ETR)
+               return -EPERM;
+
+       ret = kstrtoul(buf, 0, &val);
+       if (ret)
+               return ret;
+       /* The buffer size should be page aligned */
+       if (val & (PAGE_SIZE - 1))
+               return -EINVAL;
+       drvdata->size = val;
+       return size;
+}
+
+static DEVICE_ATTR_RW(buffer_size);
+
 static struct attribute *coresight_tmc_attrs[] = {
        &dev_attr_trigger_cntr.attr,
+       &dev_attr_buffer_size.attr,
        NULL,
 };
 
-- 
2.13.6