[PATCH] x86: add coreboot framebuffer support

[Gerd Hoffmann]

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);

[Patrick Georgi]

Am 04.09.2014 um 12:25 schrieb Gerd Hoffmann:
>  Add coreboot framebuffer support to the linux kernel.	 Say Y here

Alternatively, we teach the linux payload trampoline to add those to the setup block (it's a TODO in the trampoline code)

Patrick

[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);

[Gerd Hoffmann]

On Do, 2014-09-04 at 22:09 +0200, Vladimir 'φ-coder/phcoder' Serbinenko
wrote:
> This code assumes that payload didn't change video mode which is
> improper assumption if you're not a payload.

The code tries to detect that case.  If either the vga is in text mode
or it finds vesafb / efifb informations it assumes being booted
indirectly (via seabios for example), with possibly changed video mode,
and doesn't register the framebuffer.

Suggestions how to improve that?

cheers,
  Gerd

[H. Peter Anvin]

On 09/04/2014 03:25 AM, 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

This should NOT be named CONFIG_COREBOOT.  CONFIG_FB_COREBOOT perhaps.
> +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" */

This stuff belongs in a header file.

I'm not a fan of Coreboot having invented its own nonstandard hacks, but
I guess it is pretty much unavoidable.

-hpa

[ron minnich]

On Fri, Sep 5, 2014 at 1:05 PM, H. Peter Anvin  wrote:
> I'm not a fan of Coreboot having invented its own nonstandard hacks, but
> I guess it is pretty much unavoidable.

I suspect this should not be architecture-dependent, since coreboot
tables work across 3 coreboot architectures at present with more on
the way.

Sometimes, something that spans more than an x86 can look like a
non-standard hack. At other times, it might look portable. Depends on
ones perspective I guess.

Gerd, I'll get back to you offline to show you what we did in Akaros.

ron

[Vladimir 'φ-coder/phcoder' Serbinenko]

> I'm not a fan of Coreboot having invented its own nonstandard hacks, but
> I guess it is pretty much unavoidable.

It's completely avoidable. The stub can copy this information to
standard framebuffer info structure. The only missing thing is to apply
patch by cjwatson or mjg59 (I'm not sure now who wrote it) for having an
ID for linear framebuffer which implies no specific hardware (it can be
any) or firmware (coreboot doesn't provide nay additional info or callback).

Please don't apply this patch it will break SeaBIOS booting with VGABIOS.

[ron minnich]

Vladimir can you point me to that patch? This sounds interesting.

ron

[H. Peter Anvin]

On 09/05/2014 02:09 PM, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> > I'm not a fan of Coreboot having invented its own nonstandard
> > hacks, but I guess it is pretty much unavoidable.
>
> It's completely avoidable. The stub can copy this information to 
> standard framebuffer info structure. The only missing thing is to
> apply patch by cjwatson or mjg59 (I'm not sure now who wrote it)
> for having an ID for linear framebuffer which implies no specific
> hardware (it can be any) or firmware (coreboot doesn't provide nay
> additional info or callback).
>
> Please don't apply this patch it will break SeaBIOS booting with
> VGABIOS.

Thanks for the warning.  Yes, this is the Right Thing.

-hpa