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spi: dw: Save bandwidth with the TMOD_TO feature

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TMOD_TO is the transmit-only mode that doesn't put data into the receive
FIFO. Using TMOD_TO when the user doesn't want the received data saves
CPU time and memory bandwidth.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
This commit is contained in:
Phil Elwell
2024-07-01 15:49:14 +01:00
committed by Dom Cobley
parent 0a2acfc88e
commit 87b5bc13cd
1 changed files with 17 additions and 10 deletions
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17
drivers/spi/spi-dw-core.c
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@@ -227,6 +227,7 @@ static irqreturn_t dw_spi_transfer_handler(struct dw_spi *dws)
* final stage of the transfer. By doing so we'll get the next IRQ
* right when the leftover incoming data is received.
*/
if (dws->rx_len) {
dw_reader(dws);
if (!dws->rx_len) {
dw_spi_mask_intr(dws, 0xff);
@@ -234,6 +235,10 @@ static irqreturn_t dw_spi_transfer_handler(struct dw_spi *dws)
} else if (dws->rx_len <= dw_readl(dws, DW_SPI_RXFTLR)) {
dw_writel(dws, DW_SPI_RXFTLR, dws->rx_len - 1);
}
} else if (!dws->tx_len) {
dw_spi_mask_intr(dws, DW_SPI_INT_TXEI);
spi_finalize_current_transfer(dws->host);
}
/*
* Send data out if Tx FIFO Empty IRQ is received. The IRQ will be
@@ -241,12 +246,9 @@ static irqreturn_t dw_spi_transfer_handler(struct dw_spi *dws)
* have the TXE IRQ flood at the final stage of the transfer.
*/
if (irq_status & DW_SPI_INT_TXEI) {
dw_writer(dws);
if (!dws->tx_len) {
if (!dws->tx_len)
dw_spi_mask_intr(dws, DW_SPI_INT_TXEI);
if (!dws->rx_len)
spi_finalize_current_transfer(dws->host);
}
dw_writer(dws);
}
return IRQ_HANDLED;
@@ -436,6 +438,11 @@ static int dw_spi_transfer_one(struct spi_controller *host,
dws->rx = transfer->rx_buf;
dws->rx_len = dws->tx_len;
if (!dws->rx) {
dws->rx_len = 0;
cfg.tmode = DW_SPI_CTRLR0_TMOD_TO;
}
/* Ensure the data above is visible for all CPUs */
smp_mb();