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tegra124: implement x2 mode for SPI transfers on CBFS media

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This implements x2 mode when reading CBFS media over SPI.

In theory this effectively doubles our throughput, though the initial
results were almost negligibly better. Using a logic analyzer we see
a pattern of 12 clocks, ~70ns delay, 4 clocks, ~310ns delay. So if we
want to see further gains here then we'll probably need to tune AHB
arbitration and utilization to eliminate bubbles/stalls when copying
from APB DMA.

BUG=none
BRANCH=none
TEST=built and booted on Nyan.
Signed-off-by: David Hendricks <dhendrix@chromium.org>

Change-Id: I33d6ae30923fc42b4dc7103d029085985472cf3e
Reviewed-on: https://chromium-review.googlesource.com/177835
Reviewed-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Commit-Queue: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>
This commit is contained in:
David Hendricks 2013-11-22 17:08:16 -08:00 • committed by chrome-internal-fetch
commit 2928922336
2 changed files with 35 additions and 7 deletions
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41
src/soc/nvidia/tegra124/spi.c
View file

@ -842,19 +842,37 @@ static int tegra_spi_cbfs_close(struct cbfs_media *media)
return 0;
}
#define JEDEC_READ 0x03
#define JEDEC_READ_OUTSIZE 0x04
/* JEDEC_READ_INSIZE : any length */
#define JEDEC_READ 0x03
#define JEDEC_READ_OUTSIZE 0x04
#define JEDEC_FAST_READ_DUAL 0x3b
#define JEDEC_FAST_READ_DUAL_OUTSIZE 0x05
static size_t tegra_spi_cbfs_read(struct cbfs_media *media, void *dest,
size_t offset, size_t count)
{
struct tegra_spi_media *spi = (struct tegra_spi_media *)media->context;
u8 spi_read_cmd[JEDEC_READ_OUTSIZE];
u8 spi_read_cmd[JEDEC_FAST_READ_DUAL_OUTSIZE];
unsigned int read_cmd_bytes;
int ret = count;
struct tegra_spi_channel *channel;
/* TODO: Dual mode (BOTH_EN_BIT) and packed mode */
spi_read_cmd[0] = JEDEC_READ;
channel = to_tegra_spi(spi->slave->bus);
if (channel->dual_mode) {
/*
* Command 0x3b will interleave data only, command 0xbb will
* interleave the address as well. It's nice to see the address
* plainly when debugging, and we're mostly concerned with
* large transfers so the optimization of using 0xbb isn't
* really worthwhile.
*/
spi_read_cmd[0] = JEDEC_FAST_READ_DUAL;
spi_read_cmd[4] = 0x00; /* dummy byte */
read_cmd_bytes = JEDEC_FAST_READ_DUAL_OUTSIZE;
} else {
spi_read_cmd[0] = JEDEC_READ;
read_cmd_bytes = JEDEC_READ_OUTSIZE;
}
spi_read_cmd[1] = (offset >> 16) & 0xff;
spi_read_cmd[2] = (offset >> 8) & 0xff;
spi_read_cmd[3] = offset & 0xff;
@ -863,18 +881,23 @@ static size_t tegra_spi_cbfs_read(struct cbfs_media *media, void *dest,
spi_cs_activate(spi->slave);
if (spi_xfer(spi->slave, spi_read_cmd,
sizeof(spi_read_cmd) * 8, NULL, 0) < 0) {
read_cmd_bytes * 8, NULL, 0) < 0) {
ret = -1;
printk(BIOS_ERR, "%s: Failed to transfer %u bytes\n",
__func__, sizeof(spi_read_cmd));
goto tegra_spi_cbfs_read_exit;
}
if (channel->dual_mode) {
setbits_le32(&channel->regs->command1, SPI_CMD1_BOTH_EN_BIT);
}
if (spi_xfer(spi->slave, NULL, 0, dest, count * 8)) {
ret = -1;
printk(BIOS_ERR, "%s: Failed to transfer %u bytes\n",
__func__, count);
}
if (channel->dual_mode)
clrbits_le32(&channel->regs->command1, SPI_CMD1_BOTH_EN_BIT);
tegra_spi_cbfs_read_exit:
/* de-assert /CS */
@ -924,6 +947,10 @@ int initialize_tegra_spi_cbfs_media(struct cbfs_media *media,
media->map = tegra_spi_cbfs_map;
media->unmap = tegra_spi_cbfs_unmap;
#if CONFIG_SPI_FLASH_FAST_READ_DUAL_OUTPUT_3B == 1
channel->dual_mode = 1;
#endif
return 0;
}

1
src/soc/nvidia/tegra124/spi.h
View file

@ -57,6 +57,7 @@ struct tegra_spi_channel {
/* stuff that is specific to the attached device */
int rx_frame_header_enable;
u8 frame_header;
int dual_mode; /* for x2 transfers with bit interleaving */
/* context (used internally) */
u8 *in_buf, *out_buf;