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AXI SPI Engine offload optimization #2757

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AXI SPI Engine offload optimization #2757

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96fe2a4
spi: axi-spi-engine: offload instruction optimization
dlech Mar 31, 2025
c8e39b7
spi: axi-spi-engine: wait for completion in setup
dlech Mar 31, 2025
f712288
spi: axi-spi-engine: don't repeat mode config for offload
dlech Mar 31, 2025
37d3e94
spi: axi-spi-engine: optimize bits_per_word for offload
dlech Mar 31, 2025
1902559
spi: axi-spi-engine: omit SYNC from offload instructions
dlech Mar 31, 2025
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91 changes: 85 additions & 6 deletions drivers/spi/spi-axi-spi-engine.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include <linux/fpga/adi-axi-common.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/of.h>
#include <linux/module.h>
#include <linux/overflow.h>
Expand Down Expand Up @@ -140,6 +141,8 @@ struct spi_engine_offload {
struct spi_engine *spi_engine;
unsigned long flags;
unsigned int offload_num;
unsigned int spi_mode_config;
u8 bits_per_word;
};

struct spi_engine {
Expand All @@ -159,6 +162,7 @@ struct spi_engine {
unsigned int offload_sdo_mem_size;
struct spi_offload *offload;
u32 offload_caps;
bool offload_requires_sync;
};

static void spi_engine_program_add_cmd(struct spi_engine_program *p,
Expand Down Expand Up @@ -265,6 +269,8 @@ static int spi_engine_precompile_message(struct spi_message *msg)
{
unsigned int clk_div, max_hz = msg->spi->controller->max_speed_hz;
struct spi_transfer *xfer;
u8 min_bits_per_word = U8_MAX;
u8 max_bits_per_word = 0;

list_for_each_entry(xfer, &msg->transfers, transfer_list) {
/* If we have an offload transfer, we can't rx to buffer */
Expand All @@ -273,6 +279,24 @@ static int spi_engine_precompile_message(struct spi_message *msg)

clk_div = DIV_ROUND_UP(max_hz, xfer->speed_hz);
xfer->effective_speed_hz = max_hz / min(clk_div, 256U);

if (xfer->len) {
min_bits_per_word = min(min_bits_per_word, xfer->bits_per_word);
max_bits_per_word = max(max_bits_per_word, xfer->bits_per_word);
}
}

/*
* If all xfers in the message use the same bits_per_word, we can
* provide some optimization when using SPI offload.
*/
if (msg->offload) {
struct spi_engine_offload *priv = msg->offload->priv;

if (min_bits_per_word == max_bits_per_word)
priv->bits_per_word = min_bits_per_word;
else
priv->bits_per_word = 0;
}

return 0;
Expand All @@ -283,6 +307,7 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry,
{
struct spi_device *spi = msg->spi;
struct spi_controller *host = spi->controller;
struct spi_engine_offload *priv;
struct spi_transfer *xfer;
int clk_div, new_clk_div, inst_ns;
bool keep_cs = false;
Expand All @@ -296,9 +321,24 @@ static void spi_engine_compile_message(struct spi_message *msg, bool dry,

clk_div = 1;

spi_engine_program_add_cmd(p, dry,
SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_CONFIG,
spi_engine_get_config(spi)));
/*
* As an optimization, SPI offload sets once this when the offload is
* enabled instead of repeating the instruction in each message.
*/
if (msg->offload) {
priv = msg->offload->priv;
priv->spi_mode_config = spi_engine_get_config(spi);

/*
* If all xfers use the same bits_per_word, it can be optimized
* in the same way.
*/
bits_per_word = priv->bits_per_word;
} else {
spi_engine_program_add_cmd(p, dry,
SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_CONFIG,
spi_engine_get_config(spi)));
}

xfer = list_first_entry(&msg->transfers, struct spi_transfer, transfer_list);
spi_engine_gen_cs(p, dry, spi, !xfer->cs_off);
Expand Down Expand Up @@ -663,6 +703,8 @@ static void spi_engine_offload_unprepare(struct spi_offload *offload)

static int spi_engine_optimize_message(struct spi_message *msg)
{
struct spi_controller *host = msg->spi->controller;
struct spi_engine *spi_engine = spi_controller_get_devdata(host);
struct spi_engine_program p_dry, *p;
int ret;

Expand All @@ -679,8 +721,13 @@ static int spi_engine_optimize_message(struct spi_message *msg)

spi_engine_compile_message(msg, false, p);

spi_engine_program_add_cmd(p, false, SPI_ENGINE_CMD_SYNC(
msg->offload ? 0 : AXI_SPI_ENGINE_CUR_MSG_SYNC_ID));
/*
* Non-offload needs SYNC for completion interrupt. Older versions of
* the IP core also need SYNC for offload to work properly.
*/
if (!msg->offload || spi_engine->offload_requires_sync)
spi_engine_program_add_cmd(p, false, SPI_ENGINE_CMD_SYNC(
msg->offload ? 0 : AXI_SPI_ENGINE_CUR_MSG_SYNC_ID));

msg->opt_state = p;

Expand Down Expand Up @@ -739,12 +786,16 @@ static int spi_engine_setup(struct spi_device *device)
{
struct spi_controller *host = device->controller;
struct spi_engine *spi_engine = spi_controller_get_devdata(host);
unsigned int reg;

if (device->mode & SPI_CS_HIGH)
spi_engine->cs_inv |= BIT(spi_get_chipselect(device, 0));
else
spi_engine->cs_inv &= ~BIT(spi_get_chipselect(device, 0));

writel_relaxed(SPI_ENGINE_CMD_SYNC(0),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

writel_relaxed(SPI_ENGINE_CMD_CS_INV(spi_engine->cs_inv),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

Expand All @@ -755,7 +806,11 @@ static int spi_engine_setup(struct spi_device *device)
writel_relaxed(SPI_ENGINE_CMD_ASSERT(0, 0xff),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

return 0;
writel_relaxed(SPI_ENGINE_CMD_SYNC(1),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

return readl_relaxed_poll_timeout(spi_engine->base + SPI_ENGINE_REG_SYNC_ID,
reg, reg == 1, 1, 1000);
}

static int spi_engine_transfer_one_message(struct spi_controller *host,
Expand Down Expand Up @@ -833,6 +888,27 @@ static int spi_engine_trigger_enable(struct spi_offload *offload)
struct spi_engine_offload *priv = offload->priv;
struct spi_engine *spi_engine = priv->spi_engine;
unsigned int reg;
int ret;

writel_relaxed(SPI_ENGINE_CMD_SYNC(0),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

writel_relaxed(SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_CONFIG,
priv->spi_mode_config),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

if (priv->bits_per_word)
writel_relaxed(SPI_ENGINE_CMD_WRITE(SPI_ENGINE_CMD_REG_XFER_BITS,
priv->bits_per_word),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

writel_relaxed(SPI_ENGINE_CMD_SYNC(1),
spi_engine->base + SPI_ENGINE_REG_CMD_FIFO);

ret = readl_relaxed_poll_timeout(spi_engine->base + SPI_ENGINE_REG_SYNC_ID,
reg, reg == 1, 1, 1000);
if (ret)
return ret;

reg = readl_relaxed(spi_engine->base +
SPI_ENGINE_REG_OFFLOAD_CTRL(priv->offload_num));
Expand Down Expand Up @@ -987,6 +1063,9 @@ static int spi_engine_probe(struct platform_device *pdev)
spi_engine->offload_sdo_mem_size = SPI_ENGINE_OFFLOAD_SDO_FIFO_SIZE;
}

/* IP v1.5 dropped the requirement for SYNC in offload messages. */
spi_engine->offload_requires_sync = ADI_AXI_PCORE_VER_MINOR(version) < 5;

writel_relaxed(0x00, spi_engine->base + SPI_ENGINE_REG_RESET);
writel_relaxed(0xff, spi_engine->base + SPI_ENGINE_REG_INT_PENDING);
writel_relaxed(0x00, spi_engine->base + SPI_ENGINE_REG_INT_ENABLE);
Expand Down
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