request for 4.14-stable: 2b16fd63059a ("i2c: rcar: handle RXDMA HW behaviour on Gen3")

request for 4.14-stable: 2b16fd63059a ("i2c: rcar: handle RXDMA HW behaviour on Gen3")

[Sudip Mukherjee]

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Hi Greg,

This was missing in 4.14-stable. Please apply to your queue.

--
Regards
Sudip

[-- Attachment #2: 0001-i2c-rcar-handle-RXDMA-HW-behaviour-on-Gen3.patch --]
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>From 543f5998d7597a7779a6bc8a4f8ec726b4c34c02 Mon Sep 17 00:00:00 2001
From: Wolfram Sang <wsa+renesas@sang-engineering.com>
Date: Thu, 28 Jun 2018 22:45:38 +0200
Subject: [PATCH] i2c: rcar: handle RXDMA HW behaviour on Gen3

commit 2b16fd63059ab9a46d473620749672dc342e1d21 upstream

On Gen3, we can only do RXDMA once per transfer reliably. For that, we
must reset the device, then we can have RXDMA once. This patch
implements this. When there is no reset controller or the reset fails,
RXDMA will be blocked completely. Otherwise, it will be disabled after
the first RXDMA transfer. Based on a commit from the BSP by Hiromitsu
Yamasaki, yet completely refactored to handle multiple read messages
within one transfer.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/i2c/busses/i2c-rcar.c | 54 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 15d764afec3b..7f044df1ea07 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -32,6 +32,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 #include <linux/slab.h>
 
 /* register offsets */
@@ -111,8 +112,9 @@
 #define ID_ARBLOST	(1 << 3)
 #define ID_NACK		(1 << 4)
 /* persistent flags */
+#define ID_P_NO_RXDMA	(1 << 30) /* HW forbids RXDMA sometimes */
 #define ID_P_PM_BLOCKED	(1 << 31)
-#define ID_P_MASK	ID_P_PM_BLOCKED
+#define ID_P_MASK	(ID_P_PM_BLOCKED | ID_P_NO_RXDMA)
 
 enum rcar_i2c_type {
 	I2C_RCAR_GEN1,
@@ -140,6 +142,8 @@ struct rcar_i2c_priv {
 	struct dma_chan *dma_rx;
 	struct scatterlist sg;
 	enum dma_data_direction dma_direction;
+
+	struct reset_control *rstc;
 };
 
 #define rcar_i2c_priv_to_dev(p)		((p)->adap.dev.parent)
@@ -321,6 +325,11 @@ static void rcar_i2c_dma_unmap(struct rcar_i2c_priv *priv)
 	dma_unmap_single(chan->device->dev, sg_dma_address(&priv->sg),
 			 sg_dma_len(&priv->sg), priv->dma_direction);
 
+	/* Gen3 can only do one RXDMA per transfer and we just completed it */
+	if (priv->devtype == I2C_RCAR_GEN3 &&
+	    priv->dma_direction == DMA_FROM_DEVICE)
+		priv->flags |= ID_P_NO_RXDMA;
+
 	priv->dma_direction = DMA_NONE;
 }
 
@@ -358,8 +367,9 @@ static void rcar_i2c_dma(struct rcar_i2c_priv *priv)
 	unsigned char *buf;
 	int len;
 
-	/* Do not use DMA if it's not available or for messages < 8 bytes */
-	if (IS_ERR(chan) || msg->len < 8)
+	/* Do various checks to see if DMA is feasible at all */
+	if (IS_ERR(chan) || msg->len < 8 ||
+	    (read && priv->flags & ID_P_NO_RXDMA))
 		return;
 
 	if (read) {
@@ -688,6 +698,25 @@ static void rcar_i2c_release_dma(struct rcar_i2c_priv *priv)
 	}
 }
 
+/* I2C is a special case, we need to poll the status of a reset */
+static int rcar_i2c_do_reset(struct rcar_i2c_priv *priv)
+{
+	int i, ret;
+
+	ret = reset_control_reset(priv->rstc);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < LOOP_TIMEOUT; i++) {
+		ret = reset_control_status(priv->rstc);
+		if (ret == 0)
+			return 0;
+		udelay(1);
+	}
+
+	return -ETIMEDOUT;
+}
+
 static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
 				struct i2c_msg *msgs,
 				int num)
@@ -699,6 +728,16 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
 
 	pm_runtime_get_sync(dev);
 
+	/* Gen3 needs a reset before allowing RXDMA once */
+	if (priv->devtype == I2C_RCAR_GEN3) {
+		priv->flags |= ID_P_NO_RXDMA;
+		if (!IS_ERR(priv->rstc)) {
+			ret = rcar_i2c_do_reset(priv);
+			if (ret == 0)
+				priv->flags &= ~ID_P_NO_RXDMA;
+		}
+	}
+
 	rcar_i2c_init(priv);
 
 	ret = rcar_i2c_bus_barrier(priv);
@@ -868,6 +907,15 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto out_pm_put;
 
+	if (priv->devtype == I2C_RCAR_GEN3) {
+		priv->rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+		if (!IS_ERR(priv->rstc)) {
+			ret = reset_control_status(priv->rstc);
+			if (ret < 0)
+				priv->rstc = ERR_PTR(-ENOTSUPP);
+		}
+	}
+
 	/* Stay always active when multi-master to keep arbitration working */
 	if (of_property_read_bool(dev->of_node, "multi-master"))
 		priv->flags |= ID_P_PM_BLOCKED;
-- 
2.11.0

Re: request for 4.14-stable: 2b16fd63059a ("i2c: rcar: handle RXDMA HW behaviour on Gen3")

[Greg Kroah-Hartman]

On Tue, Oct 16, 2018 at 10:38:17PM +0100, Sudip Mukherjee wrote:
> Hi Greg,
> 
> This was missing in 4.14-stable. Please apply to your queue.

Applied, thanks.

greg k-h