[v2,02/15] spi/xilinx: Leave the IRQ always enabled.

Commit Message

Ricardo Ribalda Delgado Jan. 28, 2015, 12:23 p.m. UTC

Instead of enabling the IRQ and disabling it for every transaction.

Specially the small transactions (1,2 words) benefit from removing 3 bus
accesses.

Signed-off-by: Ricardo Ribalda Delgado <[e-mail]>
---
 drivers/spi/spi-xilinx.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

Comments

Mark Brown Jan. 28, 2015, 7:38 p.m. UTC | #1

On Wed, Jan 28, 2015 at 01:23:41PM +0100, Ricardo Ribalda Delgado wrote:
> Instead of enabling the IRQ and disabling it for every transaction.
> 
> Specially the small transactions (1,2 words) benefit from removing 3 bus
> accesses.

For this particular change I don't think it matters but in general
moving things that do need to be enabled and disabled to
{un,}prepare_transfer_hardware() will avoid quite a bit of overhead
under load.

Patch

diff --git a/drivers/spi/spi-xilinx.c b/drivers/spi/spi-xilinx.c
index 1890af8..d933207 100644
--- a/drivers/spi/spi-xilinx.c
+++ b/drivers/spi/spi-xilinx.c
@@ -167,8 +167,11 @@  static void xspi_init_hw(struct xilinx_spi *xspi)
 	/* Reset the SPI device */
 	xspi->write_fn(XIPIF_V123B_RESET_MASK,
 		regs_base + XIPIF_V123B_RESETR_OFFSET);
-	/* Disable all the interrupts just in case */
-	xspi->write_fn(0, regs_base + XIPIF_V123B_IIER_OFFSET);
+	/* Enable the transmit empty interrupt, which we use to determine
+	 * progress on the transmission.
+	 */
+	xspi->write_fn(XSPI_INTR_TX_EMPTY,
+			regs_base + XIPIF_V123B_IIER_OFFSET);
 	/* Enable the global IPIF interrupt */
 	xspi->write_fn(XIPIF_V123B_GINTR_ENABLE,
 		regs_base + XIPIF_V123B_DGIER_OFFSET);
@@ -237,7 +240,6 @@  static void xilinx_spi_fill_tx_fifo(struct xilinx_spi *xspi, int n_words)
 static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
 {
 	struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);
-	u32 ipif_ier;
 
 	/* We get here with transmitter inhibited */
 
@@ -246,14 +248,6 @@  static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
 	xspi->remaining_bytes = t->len;
 	reinit_completion(&xspi->done);
 
-
-	/* Enable the transmit empty interrupt, which we use to determine
-	 * progress on the transmission.
-	 */
-	ipif_ier = xspi->read_fn(xspi->regs + XIPIF_V123B_IIER_OFFSET);
-	xspi->write_fn(ipif_ier | XSPI_INTR_TX_EMPTY,
-		xspi->regs + XIPIF_V123B_IIER_OFFSET);
-
 	for (;;) {
 		u16 cr;
 		int n_words;
@@ -290,9 +284,6 @@  static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
 			break;
 	}
 
-	/* Disable the transmit empty interrupt */
-	xspi->write_fn(ipif_ier, xspi->regs + XIPIF_V123B_IIER_OFFSET);
-
 	return t->len - xspi->remaining_bytes;
 }