[GIT PULL 21/22] intel_th: msu-sink: An example msu buffer driver

From: Alexander Shishkin
Date: Fri May 03 2019 - 04:46:43 EST


This patch adds an example "sink" MSU buffer driver, which consumes trace
data from MSC buffers.

Functionally, it acts similarly to "multi" mode with automatic window
switching.

Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
---
drivers/hwtracing/intel_th/Makefile | 3 +
drivers/hwtracing/intel_th/msu-sink.c | 137 ++++++++++++++++++++++++++
2 files changed, 140 insertions(+)
create mode 100644 drivers/hwtracing/intel_th/msu-sink.c

diff --git a/drivers/hwtracing/intel_th/Makefile b/drivers/hwtracing/intel_th/Makefile
index d9252fa8d9ca..b63eb8f309ad 100644
--- a/drivers/hwtracing/intel_th/Makefile
+++ b/drivers/hwtracing/intel_th/Makefile
@@ -20,3 +20,6 @@ intel_th_msu-y := msu.o

obj-$(CONFIG_INTEL_TH_PTI) += intel_th_pti.o
intel_th_pti-y := pti.o
+
+obj-$(CONFIG_INTEL_TH_MSU) += intel_th_msu_sink.o
+intel_th_msu_sink-y := msu-sink.o
diff --git a/drivers/hwtracing/intel_th/msu-sink.c b/drivers/hwtracing/intel_th/msu-sink.c
new file mode 100644
index 000000000000..1a7949a282c3
--- /dev/null
+++ b/drivers/hwtracing/intel_th/msu-sink.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * An example software sink buffer driver for Intel TH MSU.
+ *
+ * Copyright (C) 2019 Intel Corporation.
+ */
+
+#include <linux/intel_th.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+
+static unsigned int block_order;
+
+module_param(block_order, int, 0600);
+
+#define MAX_SGTS 16
+
+struct msu_sink_private {
+ struct device *dev;
+ struct sg_table **sgts;
+ unsigned int nr_sgts;
+ unsigned int block_order;
+};
+
+static void *msu_sink_assign(struct device *dev, int *mode)
+{
+ struct msu_sink_private *priv;
+
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return NULL;
+
+ priv->sgts = kzalloc(sizeof(void *) * MAX_SGTS, GFP_KERNEL);
+ if (!priv->sgts) {
+ kfree(priv);
+ return NULL;
+ }
+
+ priv->dev = dev;
+ priv->block_order = block_order;
+ *mode = MSC_MODE_MULTI;
+
+ return priv;
+}
+
+static void msu_sink_unassign(void *data)
+{
+ struct msu_sink_private *priv = data;
+
+ kfree(priv->sgts);
+ kfree(priv);
+}
+
+/* See also: msc.c: __msc_buffer_win_alloc() */
+static int msu_sink_alloc_window(void *data, struct sg_table **sgt, size_t size)
+{
+ struct msu_sink_private *priv = data;
+ unsigned int nents;
+ struct scatterlist *sg_ptr;
+ void *block;
+ int ret, i;
+
+ if (priv->nr_sgts == MAX_SGTS)
+ return -ENOMEM;
+
+ nents = DIV_ROUND_UP(size, PAGE_SIZE << priv->block_order);
+
+ ret = sg_alloc_table(*sgt, nents, GFP_KERNEL);
+ if (ret)
+ return -ENOMEM;
+
+ priv->sgts[priv->nr_sgts++] = *sgt;
+
+ for_each_sg((*sgt)->sgl, sg_ptr, nents, i) {
+ block = dma_alloc_coherent(priv->dev->parent->parent,
+ PAGE_SIZE << priv->block_order,
+ &sg_dma_address(sg_ptr),
+ GFP_KERNEL);
+ sg_set_buf(sg_ptr, block, PAGE_SIZE << priv->block_order);
+ if (priv->block_order)
+ split_page(virt_to_page(block), priv->block_order);
+ }
+
+ return nents;
+}
+
+/* See also: msc.c: __msc_buffer_win_free() */
+static void msu_sink_free_window(void *data, struct sg_table *sgt)
+{
+ struct msu_sink_private *priv = data;
+ struct scatterlist *sg_ptr;
+ int i;
+
+ for_each_sg(sgt->sgl, sg_ptr, sgt->nents, i) {
+ dma_free_coherent(priv->dev->parent->parent,
+ PAGE_SIZE << priv->block_order,
+ sg_virt(sg_ptr), sg_dma_address(sg_ptr));
+ }
+
+ sg_free_table(sgt);
+ priv->nr_sgts--;
+}
+
+static int msu_sink_ready(void *data, struct sg_table *sgt, size_t bytes)
+{
+ struct msu_sink_private *priv = data;
+
+ intel_th_msc_window_unlock(priv->dev, sgt);
+
+ return 0;
+}
+
+static const struct msu_buffer_driver sink_bdrv = {
+ .name = "sink",
+ .owner = THIS_MODULE,
+ .assign = msu_sink_assign,
+ .unassign = msu_sink_unassign,
+ .alloc_window = msu_sink_alloc_window,
+ .free_window = msu_sink_free_window,
+ .ready = msu_sink_ready,
+};
+
+static int msu_sink_init(void)
+{
+ return intel_th_msu_buffer_register(&sink_bdrv);
+}
+module_init(msu_sink_init);
+
+static void msu_sink_exit(void)
+{
+ intel_th_msu_buffer_unregister(&sink_bdrv);
+}
+module_exit(msu_sink_exit);
+
+MODULE_LICENSE("GPL v2");
--
2.20.1