Re: [PATCH v5 2/6] remoteproc: pru: Add APIs to get and put the PRU cores

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Hi Mathieu,


On 15/07/22 11:52, Kishon Vijay Abraham I wrote:
+Danish

Hi Mathieu,

On 14/07/22 22:50, Mathieu Poirier wrote:
On Tue, Jul 12, 2022 at 11:59:49AM -0600, Mathieu Poirier wrote:
Hi Puranjay,

Removed Puranjay (as he is no longer with TI) and adding Danish.

Regards,
Kishon

On Tue, Jun 07, 2022 at 10:26:46AM +0530, Puranjay Mohan wrote:
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 "ti,prus" property under
the client node. The pru_rproc_put() is the complementary function
to pru_rproc_get().

Co-developed-by: Suman Anna <s-anna@xxxxxx>
Signed-off-by: Suman Anna <s-anna@xxxxxx>
Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
Co-developed-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@xxxxxxxxxx>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@xxxxxxxxxx>
Co-developed-by: Puranjay Mohan <p-mohan@xxxxxx>
Signed-off-by: Puranjay Mohan <p-mohan@xxxxxx>
---
  drivers/remoteproc/pru_rproc.c | 138 +++++++++++++++++++++++++++++++--
  include/linux/pruss.h          |  56 +++++++++++++
  2 files changed, 189 insertions(+), 5 deletions(-)
  create mode 100644 include/linux/pruss.h

diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
index 1777a01fa84e..7a35b400287a 100644
--- a/drivers/remoteproc/pru_rproc.c
+++ b/drivers/remoteproc/pru_rproc.c
@@ -2,12 +2,13 @@
  /*
   * PRU-ICSS remoteproc driver for various TI SoCs
   *
- * Copyright (C) 2014-2020 Texas Instruments Incorporated - https://www.ti.com/
+ * Copyright (C) 2014-2022 Texas Instruments Incorporated - https://www.ti.com/
   *
   * Author(s):
   *	Suman Anna <s-anna@xxxxxx>
   *	Andrew F. Davis <afd@xxxxxx>
   *	Grzegorz Jaszczyk <grzegorz.jaszczyk@xxxxxxxxxx> for Texas Instruments
+ *	Puranjay Mohan <p-mohan@xxxxxx>
   */
#include <linux/bitops.h>
@@ -16,6 +17,7 @@
  #include <linux/module.h>
  #include <linux/of_device.h>
  #include <linux/of_irq.h>
+#include <linux/pruss.h>
  #include <linux/pruss_driver.h>
  #include <linux/remoteproc.h>
@@ -111,6 +113,8 @@ struct pru_private_data {
   * @rproc: remoteproc pointer for this PRU core
   * @data: PRU core specific data
   * @mem_regions: data for each of the PRU memory regions
+ * @client_np: client device node
+ * @lock: mutex to protect client usage
   * @fw_name: name of firmware image used during loading
   * @mapped_irq: virtual interrupt numbers of created fw specific mapping
   * @pru_interrupt_map: pointer to interrupt mapping description (firmware)
@@ -126,6 +130,8 @@ struct pru_rproc {
  	struct rproc *rproc;
  	const struct pru_private_data *data;
  	struct pruss_mem_region mem_regions[PRU_IOMEM_MAX];
+	struct device_node *client_np;
+	struct mutex lock; /* client access lock */
  	const char *fw_name;
  	unsigned int *mapped_irq;
  	struct pru_irq_rsc *pru_interrupt_map;
@@ -146,6 +152,125 @@ void pru_control_write_reg(struct pru_rproc *pru, unsigned int reg, u32 val)
  	writel_relaxed(val, pru->mem_regions[PRU_IOMEM_CTRL].va + reg);
  }
+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, "ti,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 || !(&pdev->dev) || !((&pdev->dev)->driver))
+		/* probably PRU not yet probed */
+		return ERR_PTR(-EPROBE_DEFER);
+
+	/* make sure it is PRU rproc */
+	if (!is_pru_rproc(&pdev->dev)) {
+		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 ti,prus property
+ * @pru_id: optional pointer to return the PRU remoteproc processor id
+ *
+ * This function looks through a client device node's "ti,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.
+ *
+ * When optional @pru_id pointer is passed the PRU remoteproc processor id is
+ * returned.
+ *
+ * Return: 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,
+			    enum pruss_pru_id *pru_id)
+{
+	struct rproc *rproc;
+	struct pru_rproc *pru;
+	struct device *dev;
+
+	try_module_get(THIS_MODULE);

There should be a module_put() in pru_rproc_put()...

... and in the error path of this function.


More comments to come tomorrow.  I'm especially worried about this API racing
with a remote processor being removed or detached.


Looking at what is done in wkup_m3_ipc_probe(), it should be possible to call
rproc_get_by_handle() here and that would make sure the remote processor doesn't
go away before the end of the function.

More comments to come...

It is possible to call rproc_get_by_handle() here instead of __pru_get_proc(), but that would not provide multiple functionality.

The API rproc_get_by_handle() returns rproc handle on success, and NULL on failure where as __pru_get_proc() returns ERR_PTR on failure which provides multiple functionality and opportunity for us to distinguish between multiple errors.

So we have these three options.

1. If we're using the API rproc_get_by_handle() and we want the multiple ERR_PTR on failure then we will need to change the API rproc_get_by_handle() and also all the functions that uses rproc_get_by_handle().

2. Keep the API rproc_get_by_handle() as it is. That will restrict us from using multiple ERR_PTR on different kinds of error.

3. Instead of using rproc_get_by_handle(), keep using __pru_get_proc(). This will make sure we have the proper ERR_PTR to retrun for different kinds of errors.

Please let me know which option to continue with.

Thanks,
Danish




Thanks,
Mathieu

+
+	rproc = __pru_rproc_get(np, index);
+	if (IS_ERR(rproc))
+		return rproc;
+
+	pru = rproc->priv;
+	dev = &rproc->dev;
+
+	mutex_lock(&pru->lock);
+
+	if (pru->client_np) {
+		mutex_unlock(&pru->lock);
+		put_device(dev);
+		return ERR_PTR(-EBUSY);
+	}
+
+	pru->client_np = np;
+
+	mutex_unlock(&pru->lock);
+
+	if (pru_id)
+		*pru_id = pru->id;
+
+	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) || !is_pru_rproc(rproc->dev.parent))
+		return;
+
+	pru = rproc->priv;
+
+	mutex_lock(&pru->lock);
+
+	if (!pru->client_np) {
+		mutex_unlock(&pru->lock);
+		return;
+	}
+
+	pru->client_np = NULL;
+	mutex_unlock(&pru->lock);
+
+	put_device(&rproc->dev);
+}
+EXPORT_SYMBOL_GPL(pru_rproc_put);
+
  static inline u32 pru_debug_read_reg(struct pru_rproc *pru, unsigned int reg)
  {
  	return readl_relaxed(pru->mem_regions[PRU_IOMEM_DEBUG].va + reg);
@@ -438,7 +563,7 @@ static void *pru_d_da_to_va(struct pru_rproc *pru, u32 da, size_t len)
  	dram0 = pruss->mem_regions[PRUSS_MEM_DRAM0];
  	dram1 = pruss->mem_regions[PRUSS_MEM_DRAM1];
  	/* PRU1 has its local RAM addresses reversed */
-	if (pru->id == 1)
+	if (pru->id == PRUSS_PRU1)
  		swap(dram0, dram1);
  	shrd_ram = pruss->mem_regions[PRUSS_MEM_SHRD_RAM2];
@@ -747,14 +872,14 @@ static int pru_rproc_set_id(struct pru_rproc *pru)
  	case RTU0_IRAM_ADDR_MASK:
  		fallthrough;
  	case PRU0_IRAM_ADDR_MASK:
-		pru->id = 0;
+		pru->id = PRUSS_PRU0;
  		break;
  	case TX_PRU1_IRAM_ADDR_MASK:
  		fallthrough;
  	case RTU1_IRAM_ADDR_MASK:
  		fallthrough;
  	case PRU1_IRAM_ADDR_MASK:
-		pru->id = 1;
+		pru->id = PRUSS_PRU1;
  		break;
  	default:
  		ret = -EINVAL;
@@ -816,6 +941,8 @@ static int pru_rproc_probe(struct platform_device *pdev)
  	pru->pruss = platform_get_drvdata(ppdev);
  	pru->rproc = rproc;
  	pru->fw_name = fw_name;
+	pru->client_np = NULL;
+	mutex_init(&pru->lock);
for (i = 0; i < ARRAY_SIZE(mem_names); i++) {
  		res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
@@ -903,7 +1030,7 @@ MODULE_DEVICE_TABLE(of, pru_rproc_match);
static struct platform_driver pru_rproc_driver = {
  	.driver = {
-		.name   = "pru-rproc",
+		.name   = PRU_RPROC_DRVNAME,
  		.of_match_table = pru_rproc_match,
  		.suppress_bind_attrs = true,
  	},
@@ -915,5 +1042,6 @@ module_platform_driver(pru_rproc_driver);
  MODULE_AUTHOR("Suman Anna <s-anna@xxxxxx>");
  MODULE_AUTHOR("Andrew F. Davis <afd@xxxxxx>");
  MODULE_AUTHOR("Grzegorz Jaszczyk <grzegorz.jaszczyk@xxxxxxxxxx>");
+MODULE_AUTHOR("Puranjay Mohan <p-mohan@xxxxxx>");
  MODULE_DESCRIPTION("PRU-ICSS Remote Processor Driver");
  MODULE_LICENSE("GPL v2");
diff --git a/include/linux/pruss.h b/include/linux/pruss.h
new file mode 100644
index 000000000000..fdc719b43db0
--- /dev/null
+++ b/include/linux/pruss.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/**
+ * PRU-ICSS Subsystem user interfaces
+ *
+ * Copyright (C) 2015-2022 Texas Instruments Incorporated - http://www.ti.com
+ *	Suman Anna <s-anna@xxxxxx>
+ */
+
+#ifndef __LINUX_PRUSS_H
+#define __LINUX_PRUSS_H
+
+#include <linux/device.h>
+#include <linux/types.h>
+
+#define PRU_RPROC_DRVNAME "pru-rproc"
+
+/*
+ * enum pruss_pru_id - PRU core identifiers
+ */
+enum pruss_pru_id {
+	PRUSS_PRU0 = 0,
+	PRUSS_PRU1,
+	PRUSS_NUM_PRUS,
+};
+
+struct device_node;
+
+#if IS_ENABLED(CONFIG_PRU_REMOTEPROC)
+
+struct rproc *pru_rproc_get(struct device_node *np, int index,
+			    enum pruss_pru_id *pru_id);
+void pru_rproc_put(struct rproc *rproc);
+
+#else
+
+static inline struct rproc *
+pru_rproc_get(struct device_node *np, int index, enum pruss_pru_id *pru_id)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline void pru_rproc_put(struct rproc *rproc) { }
+
+#endif /* CONFIG_PRU_REMOTEPROC */
+
+static inline bool is_pru_rproc(struct device *dev)
+{
+	const char *drv_name = dev_driver_string(dev);
+
+	if (strncmp(drv_name, PRU_RPROC_DRVNAME, sizeof(PRU_RPROC_DRVNAME)))
+		return false;
+
+	return true;
+}
+
+#endif /* __LINUX_PRUSS_H */
--
2.17.1




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