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>
This commit is contained in:
Julius Werner 2019-08-12 16:45:21 -07:00 committed by Patrick Georgi
parent 54ff1a0ad3
commit db7f6fb752
5 changed files with 167 additions and 1 deletions

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@ -445,6 +445,25 @@ static inline int __ffs(u32 x) { return log2(x & (u32)(-(s32)x)); }
/** @} */ /** @} */
/**
* @defgroup mmio MMIO helper functions
* @{
*/
#if !CONFIG(LP_ARCH_MIPS)
void buffer_from_fifo32(void *buffer, size_t size, void *fifo,
int fifo_stride, int fifo_width);
void buffer_to_fifo32_prefix(void *buffer, u32 prefix, int prefsz, size_t size,
void *fifo, int fifo_stride, int fifo_width);
static inline void buffer_to_fifo32(void *buffer, size_t size, void *fifo,
int fifo_stride, int fifo_width)
{
buffer_to_fifo32_prefix(buffer, size, 0, 0, fifo,
fifo_stride, fifo_width);
}
#endif
/** @} */
/** /**
* @defgroup hash Hashing functions * @defgroup hash Hashing functions
* @{ * @{

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@ -27,6 +27,7 @@
* SUCH DAMAGE. * SUCH DAMAGE.
*/ */
#include <assert.h>
#include <libpayload.h> #include <libpayload.h>
/* /*
@ -125,3 +126,54 @@ char *getenv(const char *name)
{ {
return NULL; 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

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@ -53,3 +53,8 @@ verstage-y += i2c.c
romstage-y += i2c.c romstage-y += i2c.c
ramstage-y += i2c.c ramstage-y += i2c.c
ramstage-y += i2c_bus.c ramstage-y += i2c_bus.c
bootblock-y += mmio.c
verstage-y += mmio.c
romstage-y += mmio.c
ramstage-y += mmio.c

55
src/device/mmio.c Normal file
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@ -0,0 +1,55 @@
/*
* This file is part of the coreboot project.
*
* Copyright 2019 Google LLC
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <assert.h>
#include <device/mmio.h>
/* Helper functions for various MMIO access patterns. */
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));
}
}
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;
}
}

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@ -17,5 +17,40 @@
#include <arch/mmio.h> #include <arch/mmio.h>
#include <endian.h> #include <endian.h>
#include <types.h>
#endif #ifndef __ROMCC__
/*
* 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);
/*
* 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);
/*
* Writes a transfer buffer into 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 write everything into the same register). fifo_width is
* the amount of bytes written per register (can be 1 through 4).
*/
static inline void buffer_to_fifo32(void *buffer, size_t size, void *fifo,
int fifo_stride, int fifo_width)
{
buffer_to_fifo32_prefix(buffer, size, 0, 0, fifo,
fifo_stride, fifo_width);
}
#endif /* !__ROMCC__ */
#endif /* __DEVICE_MMIO_H__ */