lib/cbfs: Add cbfs_preload()

This API will hide all the complexity of preloading a CBFS file. It
makes it so the callers simply specify the file to preload and CBFS
takes care of the rest. It will start a new thread to read the file into
the cbfs_cache. When the file is actually required (i.e., cbfs_load,
etc) it will wait for the preload thread to complete (if it hasn't
already) and perform verification/decompression using the preloaded
buffer. This design allows decompression/verification to happen in the
main BSP thread so that timestamps are correctly reflected.

BUG=b:179699789
TEST=Test with whole CL chain, verify VGA bios was preloaded and boot
time was reduced by 12ms.

Logs:
Preloading VGA ROM
CBFS DEBUG: _cbfs_preload(name='pci1002,1638.rom', force_ro=false)
CBFS: Found 'pci1002,1638.rom' @0x20ac40 size 0xd800 in mcache @0xcb7dd0f0
spi_dma_readat_dma: start: dest: 0x021c0000, source: 0x51cc80, size: 55296
took 0 us to acquire mutex
start_spi_dma_transaction: dest: 0x021c0000, source: 0x51cc80, remaining: 55296
...
spi_dma_readat_dma: end: dest: 0x021c0000, source: 0x51cc80, remaining: 0
...
CBFS DEBUG: _cbfs_alloc(name='pci1002,1638.rom', alloc=0x00000000(0x00000000), force_ro=false, type=-1)
CBFS: Found 'pci1002,1638.rom' @0x20ac40 size 0xd800 in mcache @0xcb7dd0f0
waiting for thread
took 0 us
CBFS DEBUG: get_preload_rdev(name='pci1002,1638.rom', force_ro=false) preload successful
In CBFS, ROM address for PCI: 03:00.0 = 0x021c0000
PCI expansion ROM, signature 0xaa55, INIT size 0xd800, data ptr 0x01b0
PCI ROM image, vendor ID 1002, device ID 1638,
PCI ROM image, Class Code 030000, Code Type 00
Copying VGA ROM Image from 0x021c0000 to 0xc0000, 0xd800 bytes

$ cbmem
  ...
  40:device configuration                              5,399,404 (8,575)
  65:Option ROM initialization                         5,403,474 (4,070)
  66:Option ROM copy done                              5,403,488 (14)
  ...

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I879fc1316f97417a4b82483d353abdbd02b98a31
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56491
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/include/cbfs.h b/src/include/cbfs.h
index 0d8ac60375..f6309a3e30 100644
--- a/src/include/cbfs.h
+++ b/src/include/cbfs.h
@@ -97,6 +97,21 @@ static inline void *cbfs_type_cbmem_alloc(const char *name, uint32_t cbmem_id, s
 static inline void *cbfs_ro_type_cbmem_alloc(const char *name, uint32_t cbmem_id,
 					     size_t *size_out, enum cbfs_type *type);
 
+/*
+ * Starts the processes of preloading a file into RAM.
+ *
+ * This method depends on COOP_MULTITASKING to parallelize the loading. This method is only
+ * effective when the underlying rdev supports DMA operations.
+ *
+ * When `cbfs_load`, `cbfs_alloc`, or `cbfs_map` are called after a preload has been started,
+ * they will wait for the preload to complete (if it hasn't already) and then perform
+ * verification and/or decompression.
+ *
+ * This method does not have a return value because the system should boot regardless if this
+ * method succeeds or fails.
+ */
+void cbfs_preload(const char *name);
+
 /* Removes a previously allocated CBFS mapping. Should try to unmap mappings in strict LIFO
    order where possible, since mapping backends often don't support more complicated cases. */
 void cbfs_unmap(void *mapping);