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authorJulius Werner <jwerner@chromium.org>2019-08-12 16:45:21 -0700
committerPatrick Georgi <pgeorgi@google.com>2019-08-22 10:36:22 +0000
commitdb7f6fb75282a305c2b0f5540d2f7be939f20dde (patch)
tree2c4fc9e51c6c38c9d7a10a91083c961fd914471e /payloads/libpayload/libc/lib.c
parent54ff1a0ad3bb3c1c4bc5283aaf2f03b17c3b25f1 (diff)
Add buffer_to/from_fifo32(_prefix) helpers
Many peripheral drivers across different SoCs regularly face the same task of piping a transfer buffer into (or reading it out of) a 32-bit FIFO register. Sometimes it's just one register, sometimes a whole array of registers. Sometimes you actually transfer 4 bytes per register read/write, sometimes only 2 (or even 1). Sometimes writes need to be prefixed with one or two command bytes which makes the actual payload buffer "misaligned" in relation to the FIFO and requires a bunch of tricky bit packing logic to get right. Most of the times transfer lengths are not guaranteed to be divisible by 4, which also requires a bunch of logic to treat the potential unaligned end of the transfer correctly. We have a dozen different implementations of this same pattern across coreboot. This patch introduces a new family of helper functions that aims to solve all these use cases once and for all (*fingers crossed*). Change-Id: Ia71f66c1cee530afa4c77c46a838b4de646ffcfb Signed-off-by: Julius Werner <jwerner@chromium.org> Reviewed-on: https://review.coreboot.org/c/coreboot/+/34850 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Diffstat (limited to 'payloads/libpayload/libc/lib.c')
-rw-r--r--payloads/libpayload/libc/lib.c52
1 files changed, 52 insertions, 0 deletions
diff --git a/payloads/libpayload/libc/lib.c b/payloads/libpayload/libc/lib.c
index bead1f801b..081d7dd0e2 100644
--- a/payloads/libpayload/libc/lib.c
+++ b/payloads/libpayload/libc/lib.c
@@ -27,6 +27,7 @@
* SUCH DAMAGE.
*/
+#include <assert.h>
#include <libpayload.h>
/*
@@ -125,3 +126,54 @@ char *getenv(const char *name)
{
return NULL;
}
+
+#if !CONFIG(LP_ARCH_MIPS)
+/*
+ * Reads a transfer buffer from 32-bit FIFO registers. fifo_stride is the
+ * distance in bytes between registers (e.g. pass 4 for a normal array of 32-bit
+ * registers or 0 to read everything from the same register). fifo_width is
+ * the amount of bytes read per register (can be 1 through 4).
+ */
+void buffer_from_fifo32(void *buffer, size_t size, void *fifo,
+ int fifo_stride, int fifo_width)
+{
+ u8 *p = buffer;
+ int i, j;
+
+ assert(fifo_width > 0 && fifo_width <= sizeof(u32) &&
+ fifo_stride % sizeof(u32) == 0);
+
+ for (i = 0; i < size; i += fifo_width, fifo += fifo_stride) {
+ u32 val = read32(fifo);
+ for (j = 0; j < MIN(size - i, fifo_width); j++)
+ *p++ = (u8)(val >> (j * 8));
+ }
+}
+
+/*
+ * Version of buffer_to_fifo32() that can prepend a prefix of up to fifo_width
+ * size to the transfer. This is often useful for protocols where a command word
+ * precedes the actual payload data. The prefix must be packed in the low-order
+ * bytes of the 'prefix' u32 parameter and any high-order bytes exceeding prefsz
+ * must be 0. Note that 'size' counts total bytes written, including 'prefsz'.
+ */
+void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
+ void *fifo, int fifo_stride, int fifo_width)
+{
+ u8 *p = buffer;
+ int i, j = prefsz;
+
+ assert(fifo_width > 0 && fifo_width <= sizeof(u32) &&
+ fifo_stride % sizeof(u32) == 0 && prefsz <= fifo_width);
+
+ uint32_t val = prefix;
+ for (i = 0; i < size; i += fifo_width, fifo += fifo_stride) {
+ for (; j < MIN(size - i, fifo_width); j++)
+ val |= *p++ << (j * 8);
+ write32(fifo, val);
+ val = 0;
+ j = 0;
+ }
+
+}
+#endif