commonlib/region: Allow multiple windows for xlate_region_dev

This change updates the translated region device (xlate_region_dev) to
support multiple translation windows from the 1st address space to
2nd address space. The address spaces described by the translation
windows can be non-contiguous in both spaces. This is required so that
newer x86 platforms can describe memory mapping of SPI flash into
multiple decode windows in order to support greater than 16MiB of
memory mapped space.

Since the windows can be non-contiguous, it introduces new
restrictions on the region device ops - any operation performed on the
translated region device is limited to only 1 window at a time. This
restriction is primarily because of the mmap operation. The caller
expects that the memory mapped space is contiguous, however, that is
not true anymore. Thus, even though the other operations (readat,
writeat, eraseat) can be updated to translate into multiple operations
one for each access device, all operations across multiple windows are
prohibited for the sake of consistency.

It is the responsibility of the platform to ensure that any section
that is operated on using the translated region device does not span
multiple windows in the fmap description.

One additional difference in behavior is xlate_region_device does not
perform any action in munmap call. This is because it does not keep
track of the access device that was used to service the mmap
request. Currently, xlate_region_device is used only by memory mapped
boot media on the backend. So, not doing unmap is fine. If this needs
to be changed in the future, xlate_region_device will have to accept a
pre-allocated space from the caller to keep track of all mapping
requests.

BUG=b:171534504

Change-Id: Id5b21ffca2c8d6a9dfc37a878429aed4a8301651
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47658
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 38 insertions, 25 deletions

diff --git a/src/commonlib/include/commonlib/region.h b/src/commonlib/include/commonlib/region.h
index b9a984f171..4d095b731d 100644
--- a/src/commonlib/include/commonlib/region.h
+++ b/src/commonlib/include/commonlib/region.h
@@ -6,6 +6,7 @@
 #include <sys/types.h>
 #include <stddef.h>
 #include <stdbool.h>
+#include <commonlib/bsd/helpers.h>
 #include <commonlib/mem_pool.h>
 
 /*
@@ -210,14 +211,33 @@ void mmap_helper_device_init(struct mmap_helper_region_device *mdev,
 void *mmap_helper_rdev_mmap(const struct region_device *, size_t, size_t);
 int mmap_helper_rdev_munmap(const struct region_device *, void *);
 
-/* A translated region device provides the ability to publish a region device
- * in one address space and use an access mechanism within another address
- * space. The sub region is the window within the 1st address space and
- * the request is modified prior to accessing the second address space
- * provided by access_dev. */
-struct xlate_region_device {
+/*
+ * A translated region device provides the ability to publish a region device in one address
+ * space and use an access mechanism within another address space. The sub region is the window
+ * within the 1st address space and the request is modified prior to accessing the second
+ * address space provided by access_dev.
+ *
+ * Each xlate_region_device can support multiple translation windows described using
+ * xlate_window structure. The windows need not be contiguous in either address space. However,
+ * this poses restrictions on the operations being performed i.e. callers cannot perform
+ * operations across multiple windows of a translated region device. It is possible to support
+ * readat/writeat/eraseat by translating them into multiple calls one to access device in each
+ * window. However, mmap support is tricky because the caller expects that the memory mapped
+ * region is contiguous in both address spaces. Thus, to keep the semantics consistent for all
+ * region ops, xlate_region_device does not support any operations across the window
+ * boundary.
+ *
+ * Note: The platform is expected to ensure that the fmap description does not place any
+ * section (that will be operated using the translated region device) across multiple windows.
+ */
+struct xlate_window {
 	const struct region_device *access_dev;
 	struct region sub_region;
+};
+
+struct xlate_region_device {
+	size_t window_count;
+	const struct xlate_window *window_arr;
 	struct region_device rdev;
 };
 
@@ -225,38 +245,31 @@ extern const struct region_device_ops xlate_rdev_ro_ops;
 
 extern const struct region_device_ops xlate_rdev_rw_ops;
 
-#define XLATE_REGION_DEV_INIT(access_dev_, sub_offset_, sub_size_,	\
-		parent_sz_, ops_)					\
+#define XLATE_REGION_DEV_INIT(window_arr_, parent_sz_, ops_)		\
 	{								\
-		.access_dev = access_dev_,				\
-		.sub_region = {						\
-			.offset = (sub_offset_),			\
-			.size = (sub_size_),				\
-		},							\
+		.window_count = ARRAY_SIZE(window_arr_),		\
+		.window_arr = window_arr_,				\
 		.rdev = REGION_DEV_INIT((ops_), 0,  (parent_sz_)),	\
 	}
 
-#define XLATE_REGION_DEV_RO_INIT(access_dev_, sub_offset_, sub_size_,	\
-		parent_sz_)						\
-		XLATE_REGION_DEV_INIT(access_dev_, sub_offset_,		\
-			sub_size_, parent_sz_, &xlate_rdev_ro_ops),	\
+#define XLATE_REGION_DEV_RO_INIT(window_arr_, parent_sz_)		\
+		XLATE_REGION_DEV_INIT(window_arr_, parent_sz_, &xlate_rdev_ro_ops)
 
-#define XLATE_REGION_DEV_RW_INIT(access_dev_, sub_offset_, sub_size_,	\
-		parent_sz_)						\
-		XLATE_REGION_DEV_INIT(access_dev_, sub_offset_,		\
-			sub_size_, parent_sz_, &xlate_rdev_rw_ops),	\
+#define XLATE_REGION_DEV_RW_INIT(window_count_, window_arr_, parent_sz_) \
+		XLATE_REGION_DEV_INIT(window_arr_, parent_sz_, &xlate_rdev_rw_ops)
 
 /* Helper to dynamically initialize xlate region device. */
 void xlate_region_device_ro_init(struct xlate_region_device *xdev,
-			      const struct region_device *access_dev,
-			      size_t sub_offset, size_t sub_size,
+			      size_t window_count, const struct xlate_window *window_arr,
 			      size_t parent_size);
 
 void xlate_region_device_rw_init(struct xlate_region_device *xdev,
-			      const struct region_device *access_dev,
-			      size_t sub_offset, size_t sub_size,
+			      size_t window_count, const struct xlate_window *window_arr,
 			      size_t parent_size);
 
+void xlate_window_init(struct xlate_window *window, const struct region_device *access_dev,
+			      size_t sub_region_offset, size_t sub_region_size);
+
 /* This type can be used for incoherent access where the read and write
  * operations are backed by separate drivers. An example is x86 systems
  * with memory mapped media for reading but use a spi flash driver for