linux-kernel - [PATCH v2 6/6] i2c: iproc: handle rx fifo full interrupt

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Date:   Fri, 30 Oct 2020 12:23:39 +0530
From:   Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>
To:     Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Wolfram Sang <wsa@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Lori Hikichi <lori.hikichi@...adcom.com>,
        Dhananjay Phadke <dphadke@...ux.microsoft.com>,
        linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>
Subject: [PATCH v2 6/6] i2c: iproc: handle rx fifo full interrupt

Add code to handle IS_S_RX_FIFO_FULL_SHIFT interrupt to support
master write request with >= 64 bytes.

Iproc has a slave rx fifo size of 64 bytes.
Rx fifo full interrupt (IS_S_RX_FIFO_FULL_SHIFT) will be generated
when RX fifo becomes full. This can happen if master issues write
request of more than 64 bytes.

Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>
---
 drivers/i2c/busses/i2c-bcm-iproc.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
index 22e04055b447..cceaf69279a9 100644
--- a/drivers/i2c/busses/i2c-bcm-iproc.c
+++ b/drivers/i2c/busses/i2c-bcm-iproc.c
@@ -313,6 +313,8 @@ static void bcm_iproc_i2c_slave_init(
 
 	/* Enable interrupt register to indicate a valid byte in receive fifo */
 	val = BIT(IE_S_RX_EVENT_SHIFT);
+	/* Enable interrupt register to indicate Slave Rx FIFO Full */
+	val |= BIT(IE_S_RX_FIFO_FULL_SHIFT);
 	/* Enable interrupt register to indicate a Master read transaction */
 	val |= BIT(IE_S_RD_EVENT_SHIFT);
 	/* Enable interrupt register for the Slave BUSY command */
@@ -434,9 +436,15 @@ static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
 	 *                    events
 	 * Master-read      : both IS_S_RX_EVENT_SHIFT and IS_S_RD_EVENT_SHIFT
 	 *                    events or only IS_S_RD_EVENT_SHIFT
+	 *
+	 * iproc has a slave rx fifo size of 64 bytes. Rx fifo full interrupt
+	 * (IS_S_RX_FIFO_FULL_SHIFT) will be generated when RX fifo becomes
+	 * full. This can happen if Master issues write requests of more than
+	 * 64 bytes.
 	 */
 	if (status & BIT(IS_S_RX_EVENT_SHIFT) ||
-	    status & BIT(IS_S_RD_EVENT_SHIFT)) {
+	    status & BIT(IS_S_RD_EVENT_SHIFT) ||
+	    status & BIT(IS_S_RX_FIFO_FULL_SHIFT)) {
 		/* disable slave interrupts */
 		val = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET);
 		val &= ~iproc_i2c->slave_int_mask;
@@ -452,9 +460,14 @@ static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
 		/* schedule tasklet to read data later */
 		tasklet_schedule(&iproc_i2c->slave_rx_tasklet);
 
-		/* clear only IS_S_RX_EVENT_SHIFT interrupt */
-		iproc_i2c_wr_reg(iproc_i2c, IS_OFFSET,
-				 BIT(IS_S_RX_EVENT_SHIFT));
+		/*
+		 * clear only IS_S_RX_EVENT_SHIFT and
+		 * IS_S_RX_FIFO_FULL_SHIFT interrupt.
+		 */
+		val = BIT(IS_S_RX_EVENT_SHIFT);
+		if (status & BIT(IS_S_RX_FIFO_FULL_SHIFT))
+			val |= BIT(IS_S_RX_FIFO_FULL_SHIFT);
+		iproc_i2c_wr_reg(iproc_i2c, IS_OFFSET, val);
 	}
 
 	if (status & BIT(IS_S_TX_UNDERRUN_SHIFT)) {
-- 
2.17.1


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