[PATCH 09/16] remoteproc/pru: add APIs to get and put the PRU cores

[Roger Quadros]

From: Tero Kristo <t-kristo@xxxxxx>

Add two new APIs, pru_rproc_get() and pru_rproc_put(), to the PRU
driver to allow client drivers to acquire and release the remoteproc
device associated with a PRU core. The PRU cores are treated as
resources with only one client owning it at a time.

The pru_rproc_get() function returns the rproc handle corresponding
to a PRU core identified by the device tree "prus" property under
the client node. The pru_rproc_put() is the complementary function
to pru_rproc_get().

Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
[s-anna@xxxxxx: improve error checking, various fixes and cleanups]
Signed-off-by: Suman Anna <s-anna@xxxxxx>
---
 drivers/remoteproc/pru_rproc.c | 112 +++++++++++++++++++++++++++++++++++++++++
 include/linux/pruss.h          |   9 ++++
 2 files changed, 121 insertions(+)

diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
index fa3559b..2aa05b0 100644
--- a/drivers/remoteproc/pru_rproc.c
+++ b/drivers/remoteproc/pru_rproc.c
@@ -57,6 +57,7 @@ enum pru_mem {
  * @id: id of the PRU core within the PRUSS
  * @pruss: back-reference to parent PRUSS structure
  * @rproc: remoteproc pointer for this PRU core
+ * @client_np: client device node
  * @mbox: mailbox channel handle used for vring signalling with MPU
  * @client: mailbox client to request the mailbox channel
  * @irq_ring: IRQ number to use for processing vring buffers
@@ -71,6 +72,7 @@ enum pru_mem {
  * @sdram_da: device address of secondary Data RAM for this PRU
  * @shrdram_da: device address of shared Data RAM
  * @fw_name: name of firmware image used during loading
+ * @lock: mutex to protect client usage
  * @dbg_single_step: debug state variable to set PRU into single step mode
  * @dbg_continuous: debug state variable to restore PRU execution mode
  */
@@ -78,6 +80,7 @@ struct pru_rproc {
 	int id;
 	struct pruss *pruss;
 	struct rproc *rproc;
+	struct device_node *client_np;
 	struct mbox_chan *mbox;
 	struct mbox_client client;
 	int irq_vring;
@@ -92,6 +95,7 @@ struct pru_rproc {
 	u32 sdram_da;
 	u32 shrdram_da;
 	const char *fw_name;
+	struct mutex lock; /* client access lock */
 	u32 dbg_single_step;
 	u32 dbg_continuous;
 };
@@ -126,6 +130,113 @@ void pru_control_set_reg(struct pru_rproc *pru, unsigned int reg,
 	spin_unlock_irqrestore(&pru->rmw_lock, flags);
 }
 
+static struct rproc *__pru_rproc_get(struct device_node *np, int index)
+{
+	struct device_node *rproc_np = NULL;
+	struct platform_device *pdev;
+	struct rproc *rproc;
+
+	rproc_np = of_parse_phandle(np, "prus", index);
+	if (!rproc_np || !of_device_is_available(rproc_np))
+		return ERR_PTR(-ENODEV);
+
+	pdev = of_find_device_by_node(rproc_np);
+	of_node_put(rproc_np);
+
+	if (!pdev)
+		/* probably PRU not yet probed */
+		return ERR_PTR(-EPROBE_DEFER);
+
+	/* TODO: replace the crude string based check to make sure it is PRU */
+	if (!strstr(dev_name(&pdev->dev), "pru")) {
+		put_device(&pdev->dev);
+		return ERR_PTR(-ENODEV);
+	}
+
+	rproc = platform_get_drvdata(pdev);
+	put_device(&pdev->dev);
+	if (!rproc)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	get_device(&rproc->dev);
+
+	return rproc;
+}
+
+/**
+ * pru_rproc_get() - get the PRU rproc instance from a device node
+ * @np: the user/client device node
+ * @index: index to use for the prus property
+ *
+ * This function looks through a client device node's "prus" property at index
+ * @index and returns the rproc handle for a valid PRU remote processor if
+ * found. The function allows only one user to own the PRU rproc resource at
+ * a time. Caller must call pru_rproc_put() when done with using the rproc,
+ * not required if the function returns a failure.
+ *
+ * Returns the rproc handle on success, and an ERR_PTR on failure using one
+ * of the following error values
+ *    -ENODEV if device is not found
+ *    -EBUSY if PRU is already acquired by anyone
+ *    -EPROBE_DEFER is PRU device is not probed yet
+ */
+struct rproc *pru_rproc_get(struct device_node *np, int index)
+{
+	struct rproc *rproc;
+	struct pru_rproc *pru;
+
+	rproc = __pru_rproc_get(np, index);
+	if (IS_ERR(rproc))
+		return rproc;
+
+	pru = rproc->priv;
+
+	mutex_lock(&pru->lock);
+
+	if (pru->client_np) {
+		mutex_unlock(&pru->lock);
+		put_device(&rproc->dev);
+		return ERR_PTR(-EBUSY);
+	}
+
+	pru->client_np = np;
+
+	mutex_unlock(&pru->lock);
+
+	return rproc;
+}
+EXPORT_SYMBOL_GPL(pru_rproc_get);
+
+/**
+ * pru_rproc_put() - release the PRU rproc resource
+ * @rproc: the rproc resource to release
+ *
+ * Releases the PRU rproc resource and makes it available to other
+ * users.
+ */
+void pru_rproc_put(struct rproc *rproc)
+{
+	struct pru_rproc *pru;
+
+	if (IS_ERR_OR_NULL(rproc))
+		return;
+
+	/* TODO: replace the crude string based check to make sure it is PRU */
+	if (!strstr(dev_name(rproc->dev.parent), "pru"))
+		return;
+
+	pru = rproc->priv;
+	if (!pru->client_np)
+		return;
+
+	mutex_lock(&pru->lock);
+	pru->client_np = NULL;
+	mutex_unlock(&pru->lock);
+
+	put_device(&rproc->dev);
+}
+EXPORT_SYMBOL_GPL(pru_rproc_put);
+
 /**
  * pru_rproc_set_ctable() - set the constant table index for the PRU
  * @rproc: the rproc instance of the PRU
@@ -588,6 +699,7 @@ static int pru_rproc_probe(struct platform_device *pdev)
 	pru->rproc = rproc;
 	pru->fw_name = fw_name;
 	spin_lock_init(&pru->rmw_lock);
+	mutex_init(&pru->lock);
 
 	ret = pruss_request_mem_region(pru->pruss, PRUSS_MEM_DRAM0,
 				       &pru->dram0);
diff --git a/include/linux/pruss.h b/include/linux/pruss.h
index af04a1c..405039a 100644
--- a/include/linux/pruss.h
+++ b/include/linux/pruss.h
@@ -249,10 +249,19 @@ int pruss_intc_unconfigure(struct pruss *pruss,
 
 #if IS_ENABLED(CONFIG_PRUSS_REMOTEPROC)
 
+struct rproc *pru_rproc_get(struct device_node *node, int index);
+void pru_rproc_put(struct rproc *rproc);
 int pru_rproc_set_ctable(struct rproc *rproc, enum pru_ctable_idx c, u32 addr);
 
 #else
 
+static inline struct rproc *pru_rproc_get(struct device_node *node, int index)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
+static inline void pru_rproc_put(struct rproc *rproc) { }
+
 static inline int pru_rproc_set_ctable(struct rproc *rproc,
 				       enum pru_ctable_idx c, u32 addr)
 {
-- 
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