Re: [coreboot] [PATCH] x86: add coreboot framebuffer support

[Vladimir 'φ-coder/phcoder' Serbinenko]

This code assumes that payload didn't change video mode which is
improper assumption if you're not a payload.
On 04.09.2014 12:25, Gerd Hoffmann wrote:
> Signed-off-by: Gerd Hoffmann
>
> arch/x86/Kconfig           |  12 +++
>  arch/x86/kernel/Makefile   |   1 +
>  arch/x86/kernel/coreboot.c | 232 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 245 insertions(+)
>  create mode 100644 arch/x86/kernel/coreboot.c
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 778178f..3aeb038 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2372,6 +2372,18 @@ config X86_SYSFB
>  If unsure, say Y.
>
> +config COREBOOT
> bool "coreboot"
> depends on X86_SYSFB
> depends on FB_SIMPLE
> help
>  Add coreboot framebuffer support to the linux kernel.	 Say Y here
>  if you want the linux kernel find and use the firmware framebuffer
>  initialized by coreboot.  Useful when using the linux kernel as
>  coreboot payload.
>  If unsure, or if you don't know what coreboot is, say N.
>
> endmenu
>
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index ada2e2d..4b30b0e 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -103,6 +103,7 @@ obj-$(CONFIG_UPROBES)			+= uprobes.o
>  obj-y					+= sysfb.o
>  obj-$(CONFIG_X86_SYSFB)			+= sysfb_simplefb.o
>  obj-$(CONFIG_EFI)			+= sysfb_efi.o
> +obj-$(CONFIG_COREBOOT)			+= coreboot.o
>
> obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o
>  obj-$(CONFIG_TRACING)			+= tracepoint.o
> diff --git a/arch/x86/kernel/coreboot.c b/arch/x86/kernel/coreboot.c
> new file mode 100644
> index 0000000..44ed3fa
> --- /dev/null
> +++ b/arch/x86/kernel/coreboot.c
> @@ -0,0 +1,232 @@
> +/*
> Find and parse coreboot tables.  Register framebuffer if present.
> See src/include/boot/coreboot_tables.h in coreboot source tree.
> */
>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/mm.h>
> +#include <linux/screen_info.h>
> +#include <linux/platform_device.h>
> +#include <linux/platform_data/simplefb.h>
> +#include <video/vga.h>
>
> +#include <asm/checksum.h>
> +#include <asm/io.h>
> +#include <asm/sysfb.h>
>
> +struct cb_header {
> u32     signature;
> u32     header_bytes;
> u32     header_checksum;
> u32     table_bytes;
> u32     table_checksum;
> u32     table_entries;
>
> +};
>
> +#define CB_TAG_MAINBOARD        0x0003
> +#define CB_TAG_VERSION          0x0004
> +#define CB_TAG_FORWARD          0x0011
> +#define CB_TAG_FRAMEBUFFER      0x0012
>
> +struct cb_mainboard {
> u8      vendor_idx;
> u8      part_idx;
> char    strings[0];
>
> +};
>
> +struct cb_framebuffer {
> u64     physical_address;
> u32     x_resolution;
> u32     y_resolution;
> u32     bytes_per_line;
> u8      bits_per_pixel;
> u8      red_mask_pos;
> u8      red_mask_size;
> u8      green_mask_pos;
> u8      green_mask_size;
> u8      blue_mask_pos;
> u8      blue_mask_size;
> u8      reserved_mask_pos;
> u8      reserved_mask_size;
>
> +};
>
> +struct cb_entry {
> u32     tag;
> u32     size;
> union {
> char    string[0];
> u64     forward;
> struct cb_mainboard   mb;
> struct cb_framebuffer fb;
> } u;
>
> +};
>
> +#define CB_SIGNATURE 0x4f49424C  /* "LBIO" */
>
> +/* Try to locate the coreboot header in a given address range. */
> +static __init struct cb_header *coreboot_find_header(u32 addr, int len)
> +{
> struct cb_header *cbh, *copy;
> int offset;
> void *map;
> map = ioremap(addr, len);
> for (offset = 0; offset < len; offset += 16) {
> cbh = map + offset;
> if (!cbh)
> 	continue;
> if (cbh->signature != CB_SIGNATURE)
> 	continue;
> if (!cbh->table_bytes)
> 	continue;
> if (ip_compute_csum(cbh, sizeof(*cbh)) != 0)
> 	continue;
> if (ip_compute_csum(cbh + 1, cbh->table_bytes)
>     != cbh->table_checksum)
> 	continue;
> pr_debug("coreboot: header found at 0x%x\n",
> 	 addr + offset);
> copy = kzalloc(sizeof(*cbh) + cbh->table_bytes, GFP_KERNEL);
> memcpy(copy, cbh, sizeof(*cbh) + cbh->table_bytes);
> iounmap(map);
> return copy;
> }
> iounmap(map);
> return NULL;
>
> +}
>
> +static __init bool check_vga_text_mode(void)
> +{
> uint8_t reg;
> if (screen_info.orig_video_isVGA != 1)
> return false;
> reg = inb(VGA_GFX_I);
> if (reg == 0xff)
> /* no vga present */
> return false;
> outb(VGA_GFX_MISC, VGA_GFX_I);
> reg = inb(VGA_GFX_D);
> if (reg & 0x01)
> /* vga is in gfx mode */
> return false;
> return true;
>
> +}
>
> +static __init void coreboot_fb_init(struct cb_framebuffer *fb)
> +{
> const char *reason = "";
> struct simplefb_platform_data mode;
> struct screen_info si;
> struct resource res;
> pr_info("coreboot: framebuffer: %dx%d, %d bpp, at %llx\n",
> fb->x_resolution,
> fb->y_resolution,
> fb->bits_per_pixel,
> fb->physical_address);
> if (screen_info.orig_video_isVGA == VIDEO_TYPE_VLFB) {
> reason = "have vesa lfb";
> goto skip;
> }
> if (screen_info.orig_video_isVGA == VIDEO_TYPE_EFI) {
> reason = "have efi gop";
> goto skip;
> }
> if (check_vga_text_mode()) {
> reason = "vga is in text mode";
> goto skip;
> }
> memset(&si, 0, sizeof(si));
> si.orig_video_isVGA = VIDEO_TYPE_VLFB;
> si.lfb_width        = fb->x_resolution;
> si.lfb_height       = fb->y_resolution;
> si.lfb_depth        = fb->bits_per_pixel;
> si.lfb_base         = fb->physical_address;
> si.lfb_linelength   = fb->bytes_per_line;
> si.lfb_size         =
> (fb->y_resolution * fb->bytes_per_line + 65535) / 65536;
> si.pages            = 1;
> si.red_size         = fb->red_mask_size;
> si.red_pos          = fb->red_mask_pos;
> si.green_size       = fb->green_mask_size;
> si.green_pos        = fb->green_mask_pos;
> si.blue_size        = fb->blue_mask_size;
> si.blue_pos         = fb->blue_mask_pos;
> si.rsvd_size        = fb->reserved_mask_size;
> si.rsvd_pos         = fb->reserved_mask_pos;
> if (!parse_mode(&si, &mode)) {
> reason = "mode not compatible";
> goto skip;
> }
> memset(&res, 0, sizeof(res));
> res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> res.name = "coreboot-fb";
> res.start = si.lfb_base;
> res.end = si.lfb_base + si.lfb_size * 65536 - 1;
> pr_info("coreboot: setting up simplefb\n");
> platform_device_register_resndata(NULL, "simple-framebuffer", 0,
> 			  &res, 1, &mode, sizeof(mode));
> return;
>
> +skip:
> pr_info("coreboot: skipping framebuffer setup (%s)\n", reason);
> return;
>
> +}
>
> +static __init int coreboot_detect(void)
> +{
> struct cb_header *cbh;
> struct cb_entry *cbe;
> u64 addr = 0;
> void *next;
> int i;
>
> +newheader:
> cbh = coreboot_find_header(addr, 0x1000);
> if (!cbh)
> return 0;
> next = cbh + 1;
> for (i = 0; i < cbh->table_entries; i++) {
> cbe = next;
> next += cbe->size;
> switch (cbe->tag) {
> case CB_TAG_MAINBOARD:
> 	pr_info("coreboot: mainboard: %s / %s\n",
> 		cbe->u.mb.strings + cbe->u.mb.vendor_idx,
> 		cbe->u.mb.strings + cbe->u.mb.part_idx);
> 	break;
> case CB_TAG_VERSION:
> 	pr_info("coreboot: version: %s\n",
> 		cbe->u.string);
> 	break;
> case CB_TAG_FORWARD:
> 	pr_debug("coreboot: forward to 0x%llx\n",
> 		 cbe->u.forward);
> 	addr = cbe->u.forward;
> 	kfree(cbh);
> 	goto newheader;
> case CB_TAG_FRAMEBUFFER:
> 	coreboot_fb_init(&cbe->u.fb);
> 	break;
> default:
> 	pr_debug("%s: unhandled tag 0x%x (size %d)\n",
> 		 __func__, cbe->tag, cbe->size);
> 	break;
> }
> }
> kfree(cbh);
> return 0;
>
> +}
>
> +device_initcall(coreboot_detect);