linux-kernel - [PATCH 1/2] spi: pxa2xx: Prepare for edge-triggered interrupts

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Date:   Mon, 16 Jan 2017 10:05:59 +0100
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        linux-kernel@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jarkko Nikula <jarkko.nikula@...mer.com>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>
Subject: [PATCH 1/2] spi: pxa2xx: Prepare for edge-triggered interrupts

When using the a device with edge-triggered interrupts, such as MSIs,
the interrupt handler has to ensure that there is a point in time during
its execution where all interrupts sources are silent so that a new
event can trigger a new interrupt again.

This is achieved here by looping over SSSR evaluation. We need to take
into account that SSCR1 may be changed by the transfer handler, thus we
need to redo the mask calculation, at least regarding the volatile
interrupt enable bit (TIE).

Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
---
 drivers/spi/spi-pxa2xx.c | 50 +++++++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 22 deletions(-)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index dd7b5b4..24bf549 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -737,6 +737,7 @@ static irqreturn_t ssp_int(int irq, void *dev_id)
 	struct driver_data *drv_data = dev_id;
 	u32 sccr1_reg;
 	u32 mask = drv_data->mask_sr;
+	irqreturn_t ret = IRQ_NONE;
 	u32 status;
 
 	/*
@@ -760,37 +761,42 @@ static irqreturn_t ssp_int(int irq, void *dev_id)
 
 	sccr1_reg = pxa2xx_spi_read(drv_data, SSCR1);
 
-	/* Ignore possible writes if we don't need to write */
-	if (!(sccr1_reg & SSCR1_TIE))
-		mask &= ~SSSR_TFS;
-
 	/* Ignore RX timeout interrupt if it is disabled */
 	if (!(sccr1_reg & SSCR1_TINTE))
 		mask &= ~SSSR_TINT;
 
-	if (!(status & mask))
-		return IRQ_NONE;
+	while (1) {
+		/* Ignore possible writes if we don't need to write */
+		if (!(sccr1_reg & SSCR1_TIE))
+			mask &= ~SSSR_TFS;
 
-	if (!drv_data->master->cur_msg) {
+		if (!(status & mask))
+			return ret;
 
-		pxa2xx_spi_write(drv_data, SSCR0,
-				 pxa2xx_spi_read(drv_data, SSCR0)
-				 & ~SSCR0_SSE);
-		pxa2xx_spi_write(drv_data, SSCR1,
-				 pxa2xx_spi_read(drv_data, SSCR1)
-				 & ~drv_data->int_cr1);
-		if (!pxa25x_ssp_comp(drv_data))
-			pxa2xx_spi_write(drv_data, SSTO, 0);
-		write_SSSR_CS(drv_data, drv_data->clear_sr);
+		if (!drv_data->master->cur_msg) {
 
-		dev_err(&drv_data->pdev->dev,
-			"bad message state in interrupt handler\n");
+			pxa2xx_spi_write(drv_data, SSCR0,
+					 pxa2xx_spi_read(drv_data, SSCR0)
+					 & ~SSCR0_SSE);
+			pxa2xx_spi_write(drv_data, SSCR1,
+					 pxa2xx_spi_read(drv_data, SSCR1)
+					 & ~drv_data->int_cr1);
+			if (!pxa25x_ssp_comp(drv_data))
+				pxa2xx_spi_write(drv_data, SSTO, 0);
+			write_SSSR_CS(drv_data, drv_data->clear_sr);
 
-		/* Never fail */
-		return IRQ_HANDLED;
-	}
+			dev_err(&drv_data->pdev->dev,
+				"bad message state in interrupt handler\n");
 
-	return drv_data->transfer_handler(drv_data);
+			/* Never fail */
+			return IRQ_HANDLED;
+		}
+
+		ret |= drv_data->transfer_handler(drv_data);
+
+		status = pxa2xx_spi_read(drv_data, SSSR);
+		sccr1_reg = pxa2xx_spi_read(drv_data, SSCR1);
+	}
 }
 
 /*
-- 
2.1.4