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firmware: google: memconsole: Adapt to new coreboot ring buffer format

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The upstream coreboot implementation of memconsole was enhanced from a
single-boot console to a persistent ring buffer
(https://review.coreboot.org/#/c/18301). This patch changes the kernel
memconsole driver to be able to read the new format in all cases.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Julius Werner 2017-05-02 15:16:30 -07:00 committed by Greg Kroah-Hartman
parent 7918cfc46c
commit a5061d0285
1 changed files with 39 additions and 8 deletions
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47
drivers/firmware/google/memconsole-coreboot.c
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@ -26,19 +26,50 @@
/* CBMEM firmware console log descriptor. */
struct cbmem_cons {
u32 buffer_size;
u32 buffer_cursor;
u8 buffer_body[0];
u32 size;
u32 cursor;
u8 body[0];
} __packed;
#define CURSOR_MASK ((1 << 28) - 1)
#define OVERFLOW (1 << 31)
static struct cbmem_cons __iomem *cbmem_console;
/*
* The cbmem_console structure is read again on every access because it may
* change at any time if runtime firmware logs new messages. This may rarely
* lead to race conditions where the firmware overwrites the beginning of the
* ring buffer with more lines after we have already read |cursor|. It should be
* rare and harmless enough that we don't spend extra effort working around it.
*/
static ssize_t memconsole_coreboot_read(char *buf, loff_t pos, size_t count)
{
return memory_read_from_buffer(buf, count, &pos,
cbmem_console->buffer_body,
min(cbmem_console->buffer_cursor,
cbmem_console->buffer_size));
u32 cursor = cbmem_console->cursor & CURSOR_MASK;
u32 flags = cbmem_console->cursor & ~CURSOR_MASK;
u32 size = cbmem_console->size;
struct seg { /* describes ring buffer segments in logical order */
u32 phys; /* physical offset from start of mem buffer */
u32 len; /* length of segment */
} seg[2] = { {0}, {0} };
size_t done = 0;
int i;
if (flags & OVERFLOW) {
if (cursor > size) /* Shouldn't really happen, but... */
cursor = 0;
seg[0] = (struct seg){.phys = cursor, .len = size - cursor};
seg[1] = (struct seg){.phys = 0, .len = cursor};
} else {
seg[0] = (struct seg){.phys = 0, .len = min(cursor, size)};
}
for (i = 0; i < ARRAY_SIZE(seg) && count > done; i++) {
done += memory_read_from_buffer(buf + done, count - done, &pos,
cbmem_console->body + seg[i].phys, seg[i].len);
pos -= seg[i].len;
}
return done;
}
static int memconsole_coreboot_init(phys_addr_t physaddr)
@ -51,7 +82,7 @@ static int memconsole_coreboot_init(phys_addr_t physaddr)
return -ENOMEM;
cbmem_console = memremap(physaddr,
tmp_cbmc->buffer_size + sizeof(*cbmem_console),
tmp_cbmc->size + sizeof(*cbmem_console),
MEMREMAP_WB);
memunmap(tmp_cbmc);