Applied "spi: fsl-espi: fix and improve reading from RX FIFO" to the spi tree

[Mark Brown <broonie@xxxxxxxxxx>]

The patch

   spi: fsl-espi: fix and improve reading from RX FIFO

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From f05689a662d47896da742f5338eab183ed692c1c Mon Sep 17 00:00:00 2001
From: Heiner Kallweit <hkallweit1@xxxxxxxxx>
Date: Thu, 27 Oct 2016 21:27:35 +0200
Subject: [PATCH] spi: fsl-espi: fix and improve reading from RX FIFO

Currently the driver polls in the ISR for enough bytes in the RX FIFO.
An ISR should never do this.
Change it to read as much as possible whenever the ISR is called.
This also allows to significantly simplify the code.

Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 drivers/spi/spi-fsl-espi.c | 67 ++++++++++++++--------------------------------
 1 file changed, 20 insertions(+), 47 deletions(-)

diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
index 239f0362df61..2f95b19e67f7 100644
--- a/drivers/spi/spi-fsl-espi.c
+++ b/drivers/spi/spi-fsl-espi.c
@@ -224,6 +224,24 @@ static void fsl_espi_fill_tx_fifo(struct mpc8xxx_spi *mspi, u32 events)
 		}
 }
 
+static void fsl_espi_read_rx_fifo(struct mpc8xxx_spi *mspi, u32 events)
+{
+	u32 rx_fifo_avail = SPIE_RXCNT(events);
+
+	while (rx_fifo_avail >= min(4U, mspi->rx_len) && mspi->rx_len)
+		if (mspi->rx_len >= 4) {
+			*(u32 *)mspi->rx = fsl_espi_read_reg(mspi, ESPI_SPIRF);
+			mspi->rx += 4;
+			mspi->rx_len -= 4;
+			rx_fifo_avail -= 4;
+		} else {
+			*(u8 *)mspi->rx = fsl_espi_read_reg8(mspi, ESPI_SPIRF);
+			mspi->rx += 1;
+			mspi->rx_len -= 1;
+			rx_fifo_avail -= 1;
+		}
+}
+
 static void fsl_espi_setup_transfer(struct spi_device *spi,
 					struct spi_transfer *t)
 {
@@ -423,53 +441,8 @@ static void fsl_espi_cleanup(struct spi_device *spi)
 
 static void fsl_espi_cpu_irq(struct mpc8xxx_spi *mspi, u32 events)
 {
-	/* We need handle RX first */
-	if (events & SPIE_RNE) {
-		u32 rx_data, tmp;
-		u8 rx_data_8;
-		int rx_nr_bytes = 4;
-		int ret;
-
-		/* Spin until RX is done */
-		if (SPIE_RXCNT(events) < min(4U, mspi->rx_len)) {
-			ret = spin_event_timeout(
-				!(SPIE_RXCNT(events =
-				fsl_espi_read_reg(mspi, ESPI_SPIE)) <
-						min(4U, mspi->rx_len)),
-						10000, 0); /* 10 msec */
-			if (!ret)
-				dev_err(mspi->dev,
-					 "tired waiting for SPIE_RXCNT\n");
-		}
-
-		if (mspi->rx_len >= 4) {
-			rx_data = fsl_espi_read_reg(mspi, ESPI_SPIRF);
-		} else if (!mspi->rx_len) {
-			dev_err(mspi->dev,
-				"unexpected RX(SPIE_RNE) interrupt occurred,\n"
-				"(local rxlen %d bytes, reg rxlen %d bytes)\n",
-				min(4U, mspi->rx_len), SPIE_RXCNT(events));
-			rx_nr_bytes = 0;
-		} else {
-			rx_nr_bytes = mspi->rx_len;
-			tmp = mspi->rx_len;
-			rx_data = 0;
-			while (tmp--) {
-				rx_data_8 = fsl_espi_read_reg8(mspi,
-							       ESPI_SPIRF);
-				rx_data |= (rx_data_8 << (tmp * 8));
-			}
-
-			rx_data <<= (4 - mspi->rx_len) * 8;
-		}
-
-		mspi->rx_len -= rx_nr_bytes;
-
-		if (rx_nr_bytes && mspi->rx) {
-			*(u32 *)mspi->rx = rx_data;
-			mspi->rx += 4;
-		}
-	}
+	if (mspi->rx_len)
+		fsl_espi_read_rx_fifo(mspi, events);
 
 	if (mspi->tx_len)
 		fsl_espi_fill_tx_fifo(mspi, events);
-- 
2.10.1

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