soc/amd/common/block/lpc: Add custom SPI DMA boot device

This is a copy of mmap_boot.c and mem_rdev_ro_ops. I split it up so it
was easier to review.

The next patches will add support for the SPI DMA controller. This will
provide a minor speed up vs using mmap reads. It will also provide the
facilities to perform asynchronous SPI loading.

BUG=b:179699789
TEST=Boot guybrush to OS

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Id26e2a69601d0f31e256d0010008904a447c8e21
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55854
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/amd/common/block/lpc/Kconfig

@@ -8,6 +8,12 @@ config PROVIDES_ROM_SHARING
 	help
 	  Select this option if the LPC bridge supports ROM sharing.
 
+config SOC_AMD_COMMON_BLOCK_LPC_SPI_DMA
+	bool
+	select X86_CUSTOM_BOOTMEDIA
+	help
+	  Select this option to enable SPI DMA support.
+
 config SOC_AMD_COMMON_BLOCK_HAS_ESPI
 	bool
 	help

src/soc/amd/common/block/lpc/Makefile.inc

@@ -11,6 +11,16 @@ smm-y += lpc_util.c
 
 endif # CONFIG_SOC_AMD_COMMON_BLOCK_LPC
 
+ifeq ($(CONFIG_SOC_AMD_COMMON_BLOCK_LPC_SPI_DMA),y)
+bootblock-y += spi_dma.c
+ifneq ($(CONFIG_VBOOT_STARTS_BEFORE_BOOTBLOCK),y)
+verstage-y += spi_dma.c
+endif
+romstage-y += spi_dma.c
+ramstage-y += spi_dma.c
+smm-y += spi_dma.c
+endif # CONFIG_SOC_AMD_COMMON_BLOCK_LPC_SPI_DMA
+
 ifeq ($(CONFIG_SOC_AMD_COMMON_BLOCK_USE_ESPI),y)
 
 bootblock-y += espi_util.c

src/soc/amd/common/block/lpc/spi_dma.c

@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <boot_device.h>
+#include <commonlib/helpers.h>
+#include <commonlib/region.h>
+#include <spi_flash.h>
+#include <string.h>
+#include <types.h>
+
+/* The ROM is memory mapped just below 4GiB. Form a pointer for the base. */
+#define rom_base ((void *)(uintptr_t)(0x100000000ULL - CONFIG_ROM_SIZE))
+
+static void *spi_dma_mmap(const struct region_device *rd, size_t offset, size_t size __unused)
+{
+	const struct mem_region_device *mdev;
+
+	mdev = container_of(rd, __typeof__(*mdev), rdev);
+
+	return &mdev->base[offset];
+}
+
+static int spi_dma_munmap(const struct region_device *rd __unused, void *mapping __unused)
+{
+	return 0;
+}
+
+static ssize_t spi_dma_readat_mmap(const struct region_device *rd, void *b, size_t offset,
+				   size_t size)
+{
+	const struct mem_region_device *mdev;
+
+	mdev = container_of(rd, __typeof__(*mdev), rdev);
+
+	memcpy(b, &mdev->base[offset], size);
+
+	return size;
+}
+
+const struct region_device_ops spi_dma_rdev_ro_ops = {
+	.mmap = spi_dma_mmap,
+	.munmap = spi_dma_munmap,
+	.readat = spi_dma_readat_mmap,
+};
+
+static const struct mem_region_device boot_dev = {
+	.base = rom_base,
+	.rdev = REGION_DEV_INIT(&spi_dma_rdev_ro_ops, 0, CONFIG_ROM_SIZE),
+};
+
+const struct region_device *boot_device_ro(void)
+{
+	return &boot_dev.rdev;
+}
+
+uint32_t spi_flash_get_mmap_windows(struct flash_mmap_window *table)
+{
+	table->flash_base = 0;
+	table->host_base = (uint32_t)(uintptr_t)rom_base;
+	table->size = CONFIG_ROM_SIZE;
+
+	return 1;
+}