Introduce ability to use hardware SPI mapping for read accesses.

On X86 systems the hardware maps the bootprom SPI flash chip into the
top of memory address range. This could be used for accessing all
information in the SPI flash.

The vboot-reference code requires access to FMAP sections containing
cryptographic information, and as of today, u-boot reads the whole
sections, which are 64 KB in size, even though the actual areas
accessed by vboot-reference are much smaller.

A much faster way of accessing this information would be just passing
around pointers to the appropriate memory areas. This would eliminate
one copy, and also would make sure that only the areas actually
accessed get fetched from SPI flash.

This patch provides this ability trying to keep code changes to a
minimum.

New feature is enabled by defining CONFIG_HARDWARE_MAPPED_SPI. The
firmware storage API for file reads changes when the new configuration
option is set: a pointer to pointer to buffer is passed to the
read_spi() function instead of a pointer to buffer. When the new
feature is enabled the read_spi() function sets the pointer value to
point to the requested data instead of copying the data into the
buffer.

A new data type is introduced (read_buf_type), which is set to be a
(void *) if the new feature is not enabled, or (void **) otherwise.
This type is used as the buffer pointer in the spi_read() function.

Code allocating/freeing buffers used to keep data read from SPI flash
is now conditionally compiled.

Call sites for the spi_read() function are modified to adjust the
buffer pointer parameter (pass the address of the parameter instead of
the parameter, when the new feature is enabled).

gbb field access functions can be aliased to gbb_init(), as they all
in fact do the same - read a certain section of the gbb area.

This change does not benefit the ARM implementations, and makes the
code more complicated that it should be. Some u-boot rearchitecture
along with vboot_reference API enhancements could address this. A
tracking issue
(http://code.google.com/p/chromium-os/issues/detail?id=22528) has been
opened for that.

BUG=chrome-os-partner:6585, chromium-os:22528
TEST=manual
  . build a new stumpy firmware image
  . boot the stumpy, observe it start up chromeos.
  . assess the boot timing using the cbmem.py utility (this
    modification shaves in excess of 100ms off the boot time).
  . disable the new feature, build a stumpy image, observe that is
    still boots chromeOs.
  . run emerge-terga2_kaen chromeos-u-boot to confirem that ARM
    version builds cleanly.

Change-Id: I4e6ab530d24f5771b5a86a48d3f3135101b469a6
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/11152

2 files changed, 21 insertions, 4 deletions

diff --git a/include/chromeos/firmware_storage.h b/include/chromeos/firmware_storage.h
index 2ef6e2b034..e45819079b 100644
--- a/include/chromeos/firmware_storage.h
+++ b/include/chromeos/firmware_storage.h
@@ -15,6 +15,16 @@
 
 #include <chromeos/fdt_decode.h>
 
+#ifndef CONFIG_HARDWARE_MAPPED_SPI
+typedef void *read_buf_type;
+#define BT_EXTRA
+#define FREE_IF_NEEDED(p) free(p)
+#else
+typedef void **read_buf_type;
+#define BT_EXTRA (read_buf_type) &
+#define FREE_IF_NEEDED(p)
+#endif
+
 /**
  * These read or write [count] bytes starting from [offset] of storage into or
  * from the [buf].
@@ -27,7 +37,7 @@
  */
 typedef struct firmware_storage_t {
 	int (*read)(struct firmware_storage_t *file,
-			uint32_t offset, uint32_t count, void *buf);
+			uint32_t offset, uint32_t count, read_buf_type buf);
 	int (*write)(struct firmware_storage_t *file,
 			uint32_t offset, uint32_t count, void *buf);
 	int (*close)(struct firmware_storage_t *file);
diff --git a/include/chromeos/gbb.h b/include/chromeos/gbb.h
index 0d54f8fdd8..c3bc304b38 100644
--- a/include/chromeos/gbb.h
+++ b/include/chromeos/gbb.h
@@ -24,8 +24,9 @@
  * @param gbb_offset	Offset of GBB in flashrom device
  * @return zero if this succeeds, non-zero if this fails
  */
-int gbb_init(void *gbb, firmware_storage_t *file, uint32_t gbb_offset);
+int gbb_init(read_buf_type gbb, firmware_storage_t *file, uint32_t gbb_offset);
 
+#ifndef CONFIG_HARDWARE_MAPPED_SPI
 /**
  * This loads the BMP block of GBB from flashrom.
  *
@@ -34,7 +35,7 @@ int gbb_init(void *gbb, firmware_storage_t *file, uint32_t gbb_offset);
  * @param gbb_offset	Offset of GBB in flashrom device
  * @return zero if this succeeds, non-zero if this fails
  */
-int gbb_read_bmp_block(void *gbb,
+int gbb_read_bmp_block(read_buf_type gbb,
 		firmware_storage_t *file, uint32_t gbb_offset);
 
 /*
@@ -45,9 +46,15 @@ int gbb_read_bmp_block(void *gbb,
  * @param gbb_offset	Offset of GBB in flashrom device
  * @return zero if this succeeds, non-zero if this fails
  */
-int gbb_read_recovery_key(void *gbb,
+int gbb_read_recovery_key(read_buf_type gbb,
 		firmware_storage_t *file, uint32_t gbb_offset);
 
+#else
+
+#define gbb_read_bmp_block gbb_init
+#define gbb_read_recovery_key gbb_init
+
+#endif
 /**
  * This is a sanity check of GBB blob.
  *