Map the entire gas space twice for two different section

Previously, the whole gas sapce be mapped only once in user tool,
it work with driver which set the whole gas memory to UC- in PAT.
But it does not work with driver which set WC for first 4K MRPC
region, while keep the left same as before, that's UC-.
Map twice fix this issue.

To fix this, we reserve a virtual address space for the entire GAS region
then use two MAP_FIXED calls to allocate the two different regions.

Signed-off-by: Logan Gunthorpe <[email protected]>

lib/platform/linux.c

@@ -509,6 +509,60 @@ static int linux_port_to_pff(struct switchtec_dev *dev, int partition,
 #define __force
 #endif
 
+static ssize_t resource_size(struct switchtec_linux *ldev, const char *fname)
+{
+	char respath[PATH_MAX];
+	struct stat stat;
+	int fd, ret;
+
+	ret = dev_to_sysfs_path(ldev, fname, respath,
+				sizeof(respath));
+	if (ret) {
+		errno = ret;
+		return -1;
+	}
+
+	fd = open(respath, O_RDONLY);
+	if (fd < 0)
+		return -1;
+
+	ret = fstat(fd, &stat);
+	if (ret < 0) {
+		close(fd);
+		return -1;
+	}
+
+	close(fd);
+	return stat.st_size;
+}
+
+static int mmap_resource(struct switchtec_linux *ldev, const char *fname,
+			 void *addr, size_t offset, size_t size, int writeable)
+{
+	char respath[PATH_MAX];
+	void *map;
+	int fd, ret = 0;
+
+	ret = dev_to_sysfs_path(ldev, fname, respath,
+				sizeof(respath));
+	if (ret) {
+		errno = ret;
+		return -1;
+	}
+
+	fd = open(respath, writeable ? O_RDWR : O_RDONLY);
+	if (fd < 0)
+		return -1;
+
+	map = mmap(addr, size, (writeable ? PROT_WRITE : 0) | PROT_READ,
+		   MAP_SHARED | MAP_FIXED, fd, offset);
+	if (map == MAP_FAILED)
+		ret = -1;
+
+	close(fd);
+	return ret;
+}
+
 /*
  * GAS map maps the hardware registers into user memory space.
  * Needless to say, this can be very dangerous and should only
@@ -520,43 +574,46 @@ static gasptr_t linux_gas_map(struct switchtec_dev *dev, int writeable,
 			      size_t *map_size)
 {
 	int ret;
-	int fd;
 	void *map;
-	char respath[PATH_MAX];
-	struct stat stat;
+	ssize_t msize;
 	struct switchtec_linux *ldev = to_switchtec_linux(dev);
 
-	ret = dev_to_sysfs_path(ldev, "device/resource0_wc", respath,
-				sizeof(respath));
-
-	if (ret) {
-		errno = ret;
+	msize = resource_size(ldev, "device/resource0");
+	if (msize <= 0)
 		return SWITCHTEC_MAP_FAILED;
-	}
 
-	fd = open(respath, writeable ? O_RDWR : O_RDONLY);
-	if (fd < 0)
-		return SWITCHTEC_MAP_FAILED;
-
-	ret = fstat(fd, &stat);
-	if (ret < 0)
+	/*
+	 * Reserve virtual address space for the entire GAS mapping.
+	 */
+	map = mmap(NULL, msize, PROT_NONE,
+		   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (map == MAP_FAILED)
 		return SWITCHTEC_MAP_FAILED;
 
-	map = mmap(NULL, stat.st_size,
-		   (writeable ? PROT_WRITE : 0) | PROT_READ,
-		   MAP_SHARED, fd, 0);
-	close(fd);
+	ret = mmap_resource(ldev, "device/resource0_wc", map, 0,
+			    SWITCHTEC_GAS_TOP_CFG_OFFSET, writeable);
+	if (ret)
+		goto unmap_and_exit;
 
-	if (map == MAP_FAILED)
-		return SWITCHTEC_MAP_FAILED;
+	ret = mmap_resource(ldev, "device/resource0",
+			    map + SWITCHTEC_GAS_TOP_CFG_OFFSET,
+			    SWITCHTEC_GAS_TOP_CFG_OFFSET,
+			    msize - SWITCHTEC_GAS_TOP_CFG_OFFSET,
+			    writeable);
+	if (ret)
+		goto unmap_and_exit;
 
 	if (map_size)
-		*map_size = stat.st_size;
+		*map_size = msize;
 
 	dev->gas_map = (gasptr_t __force)map;
-	dev->gas_map_size = stat.st_size;
+	dev->gas_map_size = msize;
 
 	return (gasptr_t __force)map;
+
+unmap_and_exit:
+	munmap(map, msize);
+	return SWITCHTEC_MAP_FAILED;
 }
 
 static void linux_gas_unmap(struct switchtec_dev *dev, gasptr_t map)