[PATCH v4 03/18] fpga: mgr: separate getting/locking FPGA manager

From: Alan Tull
Date: Wed Sep 13 2017 - 16:53:15 EST

Previously when the user gets a FPGA manager, it was locked
and nobody else could use it for programming.

This commit makes it straightforward to save a reference to an
FPGA manager and only lock it when programming the FPGA.

Add functions that get an FPGA manager's mutex for exclusive use:
* fpga_mgr_lock
* fpga_mgr_unlock

The following functions no longer lock an FPGA manager's mutex:
* of_fpga_mgr_get
* fpga_mgr_get
* fpga_mgr_put

Signed-off-by: Alan Tull <atull@xxxxxxxxxx>
---
v2: add static for __fpga_mgr_get
function documentation corrections
use dev_err
v3: bisectibility fix
v4: add API doc updates that were originally in a separate patch
---
Documentation/fpga/fpga-mgr.txt | 35 ++++++++++++++++++++-------
drivers/fpga/fpga-mgr.c | 52 ++++++++++++++++++++++++++++-------------
drivers/fpga/fpga-region.c | 14 +++++++++--
include/linux/fpga/fpga-mgr.h | 3 +++
4 files changed, 77 insertions(+), 27 deletions(-)

diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
index 6ebc714..cc6413e 100644
--- a/Documentation/fpga/fpga-mgr.txt
+++ b/Documentation/fpga/fpga-mgr.txt
@@ -48,8 +48,20 @@ To get/put a reference to a FPGA manager:
struct fpga_manager *fpga_mgr_get(struct device *dev);
void fpga_mgr_put(struct fpga_manager *mgr);

-Given a DT node or device, get an exclusive reference to a FPGA manager.
-fpga_mgr_put releases the reference.
+Given a DT node or device, get a reference to a FPGA manager. This pointer
+can be saved until you are ready to program the FPGA. fpga_mgr_put releases
+the reference.
+
+
+To get exclusive control of a FPGA manager:
+-------------------------------------------
+
+ int fpga_mgr_lock(struct fpga_manager *mgr);
+ void fpga_mgr_unlock(struct fpga_manager *mgr);
+
+The user should call fpga_mgr_lock and verify that it returns 0 before
+attempting to program the FPGA. Likewise, the user should call
+fpga_mgr_unlock when done programming the FPGA.


To register or unregister the low level FPGA-specific driver:
@@ -67,13 +79,21 @@ device."

How to write an image buffer to a supported FPGA
================================================
-/* Include to get the API */
#include <linux/fpga/fpga-mgr.h>

struct fpga_manager *mgr;
struct fpga_image_info *info;
int ret;

+/*
+ * Get a reference to FPGA manager. The manager is not locked, so you can
+ * hold onto this reference without it preventing programming.
+ *
+ * This example uses the device node of the manager. Alternatively, use
+ * fpga_mgr_get(dev) instead if you have the device.
+ */
+mgr = of_fpga_mgr_get(mgr_node);
+
/* struct with information about the FPGA image to program. */
info = fpga_image_info_alloc(dev);

@@ -99,17 +119,14 @@ if (image is in a scatter gather table) {

}

-/*
- * Get a reference to FPGA manager. This example uses the device node of the
- * manager. You could use fpga_mgr_get() instead if you have the device instead
- * of the device node.
- */
-mgr = of_fpga_mgr_get(mgr_node);
+/* Get exclusive control of FPGA manager */
+ret = fpga_mgr_lock(mgr);

/* Load the buffer to the FPGA */
ret = fpga_mgr_buf_load(mgr, &info, buf, count);

/* Release the FPGA manager */
+fpga_mgr_unlock(mgr);
fpga_mgr_put(mgr);

/* Deallocate the image info if you're done with it */
diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index a8dd549..d27e8d2 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -410,28 +410,19 @@ ATTRIBUTE_GROUPS(fpga_mgr);
static struct fpga_manager *__fpga_mgr_get(struct device *dev)
{
struct fpga_manager *mgr;
- int ret = -ENODEV;

mgr = to_fpga_manager(dev);
if (!mgr)
goto err_dev;

- /* Get exclusive use of fpga manager */
- if (!mutex_trylock(&mgr->ref_mutex)) {
- ret = -EBUSY;
- goto err_dev;
- }
-
if (!try_module_get(dev->parent->driver->owner))
- goto err_ll_mod;
+ goto err_dev;

return mgr;

-err_ll_mod:
- mutex_unlock(&mgr->ref_mutex);
err_dev:
put_device(dev);
- return ERR_PTR(ret);
+ return ERR_PTR(-ENODEV);
}

static int fpga_mgr_dev_match(struct device *dev, const void *data)
@@ -440,10 +431,10 @@ static int fpga_mgr_dev_match(struct device *dev, const void *data)
}

/**
- * fpga_mgr_get - get an exclusive reference to a fpga mgr
+ * fpga_mgr_get - get a reference to a fpga mgr
* @dev: parent device that fpga mgr was registered with
*
- * Given a device, get an exclusive reference to a fpga mgr.
+ * Given a device, get a reference to a fpga mgr.
*
* Return: fpga manager struct or IS_ERR() condition containing error code.
*/
@@ -464,10 +455,10 @@ static int fpga_mgr_of_node_match(struct device *dev, const void *data)
}

/**
- * of_fpga_mgr_get - get an exclusive reference to a fpga mgr
+ * of_fpga_mgr_get - get a reference to a fpga mgr
* @node: device node
*
- * Given a device node, get an exclusive reference to a fpga mgr.
+ * Given a device node, get a reference to a fpga mgr.
*
* Return: fpga manager struct or IS_ERR() condition containing error code.
*/
@@ -491,12 +482,41 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
void fpga_mgr_put(struct fpga_manager *mgr)
{
module_put(mgr->dev.parent->driver->owner);
- mutex_unlock(&mgr->ref_mutex);
put_device(&mgr->dev);
}
EXPORT_SYMBOL_GPL(fpga_mgr_put);

/**
+ * fpga_mgr_lock - Lock FPGA manager for exclusive use
+ * @mgr: fpga manager
+ *
+ * Given a pointer to FPGA Manager (from fpga_mgr_get() or
+ * of_fpga_mgr_put()) attempt to get the mutex.
+ *
+ * Return: 0 for success or -EBUSY
+ */
+int fpga_mgr_lock(struct fpga_manager *mgr)
+{
+ if (!mutex_trylock(&mgr->ref_mutex)) {
+ dev_err(&mgr->dev, "FPGA manager is in use.\n");
+ return -EBUSY;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_lock);
+
+/**
+ * fpga_mgr_unlock - Unlock FPGA manager
+ * @mgr: fpga manager
+ */
+void fpga_mgr_unlock(struct fpga_manager *mgr)
+{
+ mutex_unlock(&mgr->ref_mutex);
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
+
+/**
* fpga_mgr_register - register a low level fpga manager driver
* @dev: fpga manager device from pdev
* @name: fpga manager name
diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
index 120c496..1e1640a 100644
--- a/drivers/fpga/fpga-region.c
+++ b/drivers/fpga/fpga-region.c
@@ -125,7 +125,7 @@ static void fpga_region_put(struct fpga_region *region)
}

/**
- * fpga_region_get_manager - get exclusive reference for FPGA manager
+ * fpga_region_get_manager - get reference for FPGA manager
* @region: FPGA region
*
* Get FPGA Manager from "fpga-mgr" property or from ancestor region.
@@ -233,6 +233,7 @@ static int fpga_region_get_bridges(struct fpga_region *region,
static int fpga_region_program_fpga(struct fpga_region *region,
struct device_node *overlay)
{
+ struct device *dev = &region->dev;
struct fpga_manager *mgr;
int ret;

@@ -249,10 +250,16 @@ static int fpga_region_program_fpga(struct fpga_region *region,
goto err_put_region;
}

+ ret = fpga_mgr_lock(mgr);
+ if (ret) {
+ dev_err(dev, "FPGA manager is busy\n");
+ goto err_put_mgr;
+ }
+
ret = fpga_region_get_bridges(region, overlay);
if (ret) {
pr_err("failed to get fpga region bridges\n");
- goto err_put_mgr;
+ goto err_unlock_mgr;
}

ret = fpga_bridges_disable(&region->bridge_list);
@@ -273,6 +280,7 @@ static int fpga_region_program_fpga(struct fpga_region *region,
goto err_put_br;
}

+ fpga_mgr_unlock(mgr);
fpga_mgr_put(mgr);
fpga_region_put(region);

@@ -280,6 +288,8 @@ static int fpga_region_program_fpga(struct fpga_region *region,

err_put_br:
fpga_bridges_put(&region->bridge_list);
+err_unlock_mgr:
+ fpga_mgr_unlock(mgr);
err_put_mgr:
fpga_mgr_put(mgr);
err_put_region:
diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
index be371e6..5e2b36e 100644
--- a/include/linux/fpga/fpga-mgr.h
+++ b/include/linux/fpga/fpga-mgr.h
@@ -155,6 +155,9 @@ void fpga_image_info_free(struct fpga_image_info *info);

int fpga_mgr_load(struct fpga_manager *mgr, struct fpga_image_info *info);

+int fpga_mgr_lock(struct fpga_manager *mgr);
+void fpga_mgr_unlock(struct fpga_manager *mgr);
+
struct fpga_manager *of_fpga_mgr_get(struct device_node *node);

struct fpga_manager *fpga_mgr_get(struct device *dev);
--
2.7.4