soc/amd/common/apob: Add support for asynchronously reading APOB_NV

This CL adds a method that can start the processes of reading the APOB
from SPI. It does require more RAM in ramstage since we no longer mmap
the buffer in the happy path. This will allow us to reduce our
boot time by ~10ms. The SoC code will need to be updated to call
start_apob_cache_read at a point where it makes sense.

BUG=b:179699789
TEST=With this and the patches above I can see a 10 ms reduction in
boot time on guybrush.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I930d58b76eb4558bc4f48ed928c4d6538fefb1e5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56232
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/common/block/apob/apob_cache.c

@@ -5,12 +5,16 @@
 #include <assert.h>
 #include <boot_device.h>
 #include <bootstate.h>
+#include <commonlib/helpers.h>
 #include <commonlib/region.h>
 #include <console/console.h>
+#include <delay.h>
 #include <fmap.h>
 #include <spi_flash.h>
 #include <stdint.h>
 #include <string.h>
+#include <thread.h>
+#include <timer.h>
 #include <timestamp.h>
 
 #define DEFAULT_MRC_CACHE "RW_MRC_CACHE"
@@ -72,6 +76,50 @@ static int get_nv_rdev(struct region_device *r)
 	return 0;
 }
 
+static struct apob_thread_context {
+	uint8_t buffer[DEFAULT_MRC_CACHE_SIZE] __attribute__((aligned(64)));
+	struct thread_handle handle;
+	struct region_device apob_rdev;
+} global_apob_thread;
+
+static enum cb_err apob_thread_entry(void *arg)
+{
+	ssize_t size;
+	struct apob_thread_context *thread = arg;
+
+	printk(BIOS_DEBUG, "APOB thread running\n");
+	size = rdev_readat(&thread->apob_rdev, thread->buffer, 0,
+		    region_device_sz(&thread->apob_rdev));
+
+	printk(BIOS_DEBUG, "APOB thread done\n");
+
+	if (size == region_device_sz(&thread->apob_rdev))
+		return CB_SUCCESS;
+
+	return CB_ERR;
+}
+
+void start_apob_cache_read(void)
+{
+	struct apob_thread_context *thread = &global_apob_thread;
+
+	if (!CONFIG(COOP_MULTITASKING))
+		return;
+
+	/* We don't perform any comparison on S3 resume */
+	if (acpi_is_wakeup_s3())
+		return;
+
+	if (get_nv_rdev(&thread->apob_rdev) != 0)
+		return;
+
+	assert(ARRAY_SIZE(thread->buffer) == region_device_sz(&thread->apob_rdev));
+
+	printk(BIOS_DEBUG, "Starting APOB preload\n");
+	if (thread_run(&thread->handle, apob_thread_entry, thread))
+		printk(BIOS_ERR, "Failed to start APOB preload thread\n");
+}
+
 static void *get_apob_from_nv_rdev(struct region_device *read_rdev)
 {
 	struct apob_base_header apob_header;
@@ -111,7 +159,11 @@ static void soc_update_apob_cache(void *unused)
 
 	timestamp_add_now(TS_AMD_APOB_READ_START);
 
-	apob_rom = get_apob_from_nv_rdev(&read_rdev);
+	if (CONFIG(COOP_MULTITASKING) && thread_join(&global_apob_thread.handle) == CB_SUCCESS)
+		apob_rom = (struct apob_base_header *)global_apob_thread.buffer;
+	else
+		apob_rom = get_apob_from_nv_rdev(&read_rdev);
+
 	if (apob_rom == NULL) {
 		update_needed = true;
 	} else if (memcmp(apob_src_ram, apob_rom, apob_src_ram->size)) {
@@ -177,4 +229,9 @@ void *soc_fill_apob_cache(void)
 	 */
 	return get_apob_nv_address();
 }
+
+/*
+ * BS_POST_DEVICE was chosen because this gives start_apob_cache_read plenty of time to read
+ * the APOB from SPI.
+ */
 BOOT_STATE_INIT_ENTRY(BS_POST_DEVICE, BS_ON_EXIT, soc_update_apob_cache, NULL);

src/soc/amd/common/block/include/amdblocks/apob_cache.h

@@ -3,6 +3,8 @@
 #ifndef AMD_BLOCK_APOB_CACHE_H
 #define AMD_BLOCK_APOB_CACHE_H
 
+/* Start loading the APOB as soon as possible so it is ready by the time we need it. */
+void start_apob_cache_read(void);
 void *soc_fill_apob_cache(void);
 
 #endif /* AMD_BLOCK_APOB_CACHE_H */