[PATCH 0/2] spi: spi-omap2-mcspi: Add DMA support for AM65x

[PATCH 0/2] spi: spi-omap2-mcspi: Add DMA support for AM65x

[Vignesh Raghavendra]

This patch series adds DMA support for McSPI on AM65x.
First patch addresses a limitationn on AM65x where transfers have to be
<4K per DMA request and second patch handles possible EPROBE_DEFER when
requesting DMA channels

Vignesh Raghavendra (2):
  spi: spi-omap2-mcspi: Handle DMA size restriction on AM65x
  spi: spi-omap2-mcspi: Support probe deferral for DMA channels

 drivers/spi/spi-omap2-mcspi.c                 | 103 +++++++++++-------
 include/linux/platform_data/spi-omap2-mcspi.h |   1 +
 2 files changed, 65 insertions(+), 39 deletions(-)

-- 
2.25.0

[PATCH 1/2] spi: spi-omap2-mcspi: Handle DMA size restriction on AM65x

[Vignesh Raghavendra]

On AM654, McSPI can only support 4K - 1 bytes per transfer when DMA is
enabled. Therefore populate master->max_transfer_size callback to
inform client drivers of this restriction when DMA channels are
available.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
---
 drivers/spi/spi-omap2-mcspi.c                 | 26 +++++++++++++++++++
 include/linux/platform_data/spi-omap2-mcspi.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 7e2292c11d12..e9bc9cf984d6 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -130,6 +130,7 @@ struct omap2_mcspi {
 	int			fifo_depth;
 	bool			slave_aborted;
 	unsigned int		pin_dir:1;
+	size_t			max_xfer_len;
 };
 
 struct omap2_mcspi_cs {
@@ -1305,6 +1306,18 @@ static bool omap2_mcspi_can_dma(struct spi_master *master,
 	return (xfer->len >= DMA_MIN_BYTES);
 }
 
+static size_t omap2_mcspi_max_xfer_size(struct spi_device *spi)
+{
+	struct omap2_mcspi *mcspi = spi_master_get_devdata(spi->master);
+	struct omap2_mcspi_dma *mcspi_dma =
+		&mcspi->dma_channels[spi->chip_select];
+
+	if (mcspi->max_xfer_len && mcspi_dma->dma_rx)
+		return mcspi->max_xfer_len;
+
+	return SIZE_MAX;
+}
+
 static int omap2_mcspi_controller_setup(struct omap2_mcspi *mcspi)
 {
 	struct spi_master	*master = mcspi->master;
@@ -1373,6 +1386,11 @@ static struct omap2_mcspi_platform_config omap4_pdata = {
 	.regs_offset = OMAP4_MCSPI_REG_OFFSET,
 };
 
+static struct omap2_mcspi_platform_config am654_pdata = {
+	.regs_offset = OMAP4_MCSPI_REG_OFFSET,
+	.max_xfer_len = SZ_4K - 1,
+};
+
 static const struct of_device_id omap_mcspi_of_match[] = {
 	{
 		.compatible = "ti,omap2-mcspi",
@@ -1382,6 +1400,10 @@ static const struct of_device_id omap_mcspi_of_match[] = {
 		.compatible = "ti,omap4-mcspi",
 		.data = &omap4_pdata,
 	},
+	{
+		.compatible = "ti,am654-mcspi",
+		.data = &am654_pdata,
+	},
 	{ },
 };
 MODULE_DEVICE_TABLE(of, omap_mcspi_of_match);
@@ -1439,6 +1461,10 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 		mcspi->pin_dir = pdata->pin_dir;
 	}
 	regs_offset = pdata->regs_offset;
+	if (pdata->max_xfer_len) {
+		mcspi->max_xfer_len = pdata->max_xfer_len;
+		master->max_transfer_size = omap2_mcspi_max_xfer_size;
+	}
 
 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	mcspi->base = devm_ioremap_resource(&pdev->dev, r);
diff --git a/include/linux/platform_data/spi-omap2-mcspi.h b/include/linux/platform_data/spi-omap2-mcspi.h
index 0bf9fddb8306..3b400b1919a9 100644
--- a/include/linux/platform_data/spi-omap2-mcspi.h
+++ b/include/linux/platform_data/spi-omap2-mcspi.h
@@ -11,6 +11,7 @@ struct omap2_mcspi_platform_config {
 	unsigned short	num_cs;
 	unsigned int regs_offset;
 	unsigned int pin_dir:1;
+	size_t max_xfer_len;
 };
 
 struct omap2_mcspi_device_config {
-- 
2.25.0

[PATCH 2/2] spi: spi-omap2-mcspi: Support probe deferral for DMA channels

[Vignesh Raghavendra]

dma_request_channel() can return -EPROBE_DEFER, if DMA driver is not
ready. Currently driver just falls back to PIO mode on probe deferral.
Fix this by requesting all required channels during probe and
propagating EPROBE_DEFER error code.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
---
 drivers/spi/spi-omap2-mcspi.c | 77 +++++++++++++++++------------------
 1 file changed, 38 insertions(+), 39 deletions(-)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index e9bc9cf984d6..e9e256718ef4 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -975,20 +975,12 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi,
  * Note that we currently allow DMA only if we get a channel
  * for both rx and tx. Otherwise we'll do PIO for both rx and tx.
  */
-static int omap2_mcspi_request_dma(struct spi_device *spi)
+static int omap2_mcspi_request_dma(struct omap2_mcspi *mcspi,
+				   struct omap2_mcspi_dma *mcspi_dma)
 {
-	struct spi_master	*master = spi->master;
-	struct omap2_mcspi	*mcspi;
-	struct omap2_mcspi_dma	*mcspi_dma;
 	int ret = 0;
 
-	mcspi = spi_master_get_devdata(master);
-	mcspi_dma = mcspi->dma_channels + spi->chip_select;
-
-	init_completion(&mcspi_dma->dma_rx_completion);
-	init_completion(&mcspi_dma->dma_tx_completion);
-
-	mcspi_dma->dma_rx = dma_request_chan(&master->dev,
+	mcspi_dma->dma_rx = dma_request_chan(mcspi->dev,
 					     mcspi_dma->dma_rx_ch_name);
 	if (IS_ERR(mcspi_dma->dma_rx)) {
 		ret = PTR_ERR(mcspi_dma->dma_rx);
@@ -996,7 +988,7 @@ static int omap2_mcspi_request_dma(struct spi_device *spi)
 		goto no_dma;
 	}
 
-	mcspi_dma->dma_tx = dma_request_chan(&master->dev,
+	mcspi_dma->dma_tx = dma_request_chan(mcspi->dev,
 					     mcspi_dma->dma_tx_ch_name);
 	if (IS_ERR(mcspi_dma->dma_tx)) {
 		ret = PTR_ERR(mcspi_dma->dma_tx);
@@ -1005,20 +997,40 @@ static int omap2_mcspi_request_dma(struct spi_device *spi)
 		mcspi_dma->dma_rx = NULL;
 	}
 
+	init_completion(&mcspi_dma->dma_rx_completion);
+	init_completion(&mcspi_dma->dma_tx_completion);
+
 no_dma:
 	return ret;
 }
 
+static void omap2_mcspi_release_dma(struct spi_master *master)
+{
+	struct omap2_mcspi *mcspi = spi_master_get_devdata(master);
+	struct omap2_mcspi_dma	*mcspi_dma;
+	int i;
+
+	for (i = 0; i < master->num_chipselect; i++) {
+		mcspi_dma = &mcspi->dma_channels[i];
+
+		if (mcspi_dma->dma_rx) {
+			dma_release_channel(mcspi_dma->dma_rx);
+			mcspi_dma->dma_rx = NULL;
+		}
+		if (mcspi_dma->dma_tx) {
+			dma_release_channel(mcspi_dma->dma_tx);
+			mcspi_dma->dma_tx = NULL;
+		}
+	}
+}
+
 static int omap2_mcspi_setup(struct spi_device *spi)
 {
 	int			ret;
 	struct omap2_mcspi	*mcspi = spi_master_get_devdata(spi->master);
 	struct omap2_mcspi_regs	*ctx = &mcspi->ctx;
-	struct omap2_mcspi_dma	*mcspi_dma;
 	struct omap2_mcspi_cs	*cs = spi->controller_state;
 
-	mcspi_dma = &mcspi->dma_channels[spi->chip_select];
-
 	if (!cs) {
 		cs = kzalloc(sizeof *cs, GFP_KERNEL);
 		if (!cs)
@@ -1043,13 +1055,6 @@ static int omap2_mcspi_setup(struct spi_device *spi)
 		}
 	}
 
-	if (!mcspi_dma->dma_rx || !mcspi_dma->dma_tx) {
-		ret = omap2_mcspi_request_dma(spi);
-		if (ret)
-			dev_warn(&spi->dev, "not using DMA for McSPI (%d)\n",
-				 ret);
-	}
-
 	ret = pm_runtime_get_sync(mcspi->dev);
 	if (ret < 0) {
 		pm_runtime_put_noidle(mcspi->dev);
@@ -1066,12 +1071,8 @@ static int omap2_mcspi_setup(struct spi_device *spi)
 
 static void omap2_mcspi_cleanup(struct spi_device *spi)
 {
-	struct omap2_mcspi	*mcspi;
-	struct omap2_mcspi_dma	*mcspi_dma;
 	struct omap2_mcspi_cs	*cs;
 
-	mcspi = spi_master_get_devdata(spi->master);
-
 	if (spi->controller_state) {
 		/* Unlink controller state from context save list */
 		cs = spi->controller_state;
@@ -1080,19 +1081,6 @@ static void omap2_mcspi_cleanup(struct spi_device *spi)
 		kfree(cs);
 	}
 
-	if (spi->chip_select < spi->master->num_chipselect) {
-		mcspi_dma = &mcspi->dma_channels[spi->chip_select];
-
-		if (mcspi_dma->dma_rx) {
-			dma_release_channel(mcspi_dma->dma_rx);
-			mcspi_dma->dma_rx = NULL;
-		}
-		if (mcspi_dma->dma_tx) {
-			dma_release_channel(mcspi_dma->dma_tx);
-			mcspi_dma->dma_tx = NULL;
-		}
-	}
-
 	if (gpio_is_valid(spi->cs_gpio))
 		gpio_free(spi->cs_gpio);
 }
@@ -1303,6 +1291,9 @@ static bool omap2_mcspi_can_dma(struct spi_master *master,
 	if (spi_controller_is_slave(master))
 		return true;
 
+	master->dma_rx = mcspi_dma->dma_rx;
+	master->dma_tx = mcspi_dma->dma_tx;
+
 	return (xfer->len >= DMA_MIN_BYTES);
 }
 
@@ -1490,6 +1481,11 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 	for (i = 0; i < master->num_chipselect; i++) {
 		sprintf(mcspi->dma_channels[i].dma_rx_ch_name, "rx%d", i);
 		sprintf(mcspi->dma_channels[i].dma_tx_ch_name, "tx%d", i);
+
+		status = omap2_mcspi_request_dma(mcspi,
+						 &mcspi->dma_channels[i]);
+		if (status == -EPROBE_DEFER)
+			goto free_master;
 	}
 
 	status = platform_get_irq(pdev, 0);
@@ -1527,6 +1523,7 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 	pm_runtime_put_sync(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 free_master:
+	omap2_mcspi_release_dma(master);
 	spi_master_put(master);
 	return status;
 }
@@ -1536,6 +1533,8 @@ static int omap2_mcspi_remove(struct platform_device *pdev)
 	struct spi_master *master = platform_get_drvdata(pdev);
 	struct omap2_mcspi *mcspi = spi_master_get_devdata(master);
 
+	omap2_mcspi_release_dma(master);
+
 	pm_runtime_dont_use_autosuspend(mcspi->dev);
 	pm_runtime_put_sync(mcspi->dev);
 	pm_runtime_disable(&pdev->dev);
-- 
2.25.0

Applied "spi: spi-omap2-mcspi: Support probe deferral for DMA channels" to the spi tree

[Mark Brown]

The patch

   spi: spi-omap2-mcspi: Support probe deferral for DMA channels

has been applied to the spi tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-5.6

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 32f2fc5dc3992b4b60cc6b1a6a31be605cc9c3a2 Mon Sep 17 00:00:00 2001
From: Vignesh Raghavendra <vigneshr@ti.com>
Date: Tue, 4 Feb 2020 18:18:16 +0530
Subject: [PATCH] spi: spi-omap2-mcspi: Support probe deferral for DMA channels

dma_request_channel() can return -EPROBE_DEFER, if DMA driver is not
ready. Currently driver just falls back to PIO mode on probe deferral.
Fix this by requesting all required channels during probe and
propagating EPROBE_DEFER error code.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200204124816.16735-3-vigneshr@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-omap2-mcspi.c | 77 +++++++++++++++++------------------
 1 file changed, 38 insertions(+), 39 deletions(-)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index e9bc9cf984d6..e9e256718ef4 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -975,20 +975,12 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi,
  * Note that we currently allow DMA only if we get a channel
  * for both rx and tx. Otherwise we'll do PIO for both rx and tx.
  */
-static int omap2_mcspi_request_dma(struct spi_device *spi)
+static int omap2_mcspi_request_dma(struct omap2_mcspi *mcspi,
+				   struct omap2_mcspi_dma *mcspi_dma)
 {
-	struct spi_master	*master = spi->master;
-	struct omap2_mcspi	*mcspi;
-	struct omap2_mcspi_dma	*mcspi_dma;
 	int ret = 0;
 
-	mcspi = spi_master_get_devdata(master);
-	mcspi_dma = mcspi->dma_channels + spi->chip_select;
-
-	init_completion(&mcspi_dma->dma_rx_completion);
-	init_completion(&mcspi_dma->dma_tx_completion);
-
-	mcspi_dma->dma_rx = dma_request_chan(&master->dev,
+	mcspi_dma->dma_rx = dma_request_chan(mcspi->dev,
 					     mcspi_dma->dma_rx_ch_name);
 	if (IS_ERR(mcspi_dma->dma_rx)) {
 		ret = PTR_ERR(mcspi_dma->dma_rx);
@@ -996,7 +988,7 @@ static int omap2_mcspi_request_dma(struct spi_device *spi)
 		goto no_dma;
 	}
 
-	mcspi_dma->dma_tx = dma_request_chan(&master->dev,
+	mcspi_dma->dma_tx = dma_request_chan(mcspi->dev,
 					     mcspi_dma->dma_tx_ch_name);
 	if (IS_ERR(mcspi_dma->dma_tx)) {
 		ret = PTR_ERR(mcspi_dma->dma_tx);
@@ -1005,20 +997,40 @@ static int omap2_mcspi_request_dma(struct spi_device *spi)
 		mcspi_dma->dma_rx = NULL;
 	}
 
+	init_completion(&mcspi_dma->dma_rx_completion);
+	init_completion(&mcspi_dma->dma_tx_completion);
+
 no_dma:
 	return ret;
 }
 
+static void omap2_mcspi_release_dma(struct spi_master *master)
+{
+	struct omap2_mcspi *mcspi = spi_master_get_devdata(master);
+	struct omap2_mcspi_dma	*mcspi_dma;
+	int i;
+
+	for (i = 0; i < master->num_chipselect; i++) {
+		mcspi_dma = &mcspi->dma_channels[i];
+
+		if (mcspi_dma->dma_rx) {
+			dma_release_channel(mcspi_dma->dma_rx);
+			mcspi_dma->dma_rx = NULL;
+		}
+		if (mcspi_dma->dma_tx) {
+			dma_release_channel(mcspi_dma->dma_tx);
+			mcspi_dma->dma_tx = NULL;
+		}
+	}
+}
+
 static int omap2_mcspi_setup(struct spi_device *spi)
 {
 	int			ret;
 	struct omap2_mcspi	*mcspi = spi_master_get_devdata(spi->master);
 	struct omap2_mcspi_regs	*ctx = &mcspi->ctx;
-	struct omap2_mcspi_dma	*mcspi_dma;
 	struct omap2_mcspi_cs	*cs = spi->controller_state;
 
-	mcspi_dma = &mcspi->dma_channels[spi->chip_select];
-
 	if (!cs) {
 		cs = kzalloc(sizeof *cs, GFP_KERNEL);
 		if (!cs)
@@ -1043,13 +1055,6 @@ static int omap2_mcspi_setup(struct spi_device *spi)
 		}
 	}
 
-	if (!mcspi_dma->dma_rx || !mcspi_dma->dma_tx) {
-		ret = omap2_mcspi_request_dma(spi);
-		if (ret)
-			dev_warn(&spi->dev, "not using DMA for McSPI (%d)\n",
-				 ret);
-	}
-
 	ret = pm_runtime_get_sync(mcspi->dev);
 	if (ret < 0) {
 		pm_runtime_put_noidle(mcspi->dev);
@@ -1066,12 +1071,8 @@ static int omap2_mcspi_setup(struct spi_device *spi)
 
 static void omap2_mcspi_cleanup(struct spi_device *spi)
 {
-	struct omap2_mcspi	*mcspi;
-	struct omap2_mcspi_dma	*mcspi_dma;
 	struct omap2_mcspi_cs	*cs;
 
-	mcspi = spi_master_get_devdata(spi->master);
-
 	if (spi->controller_state) {
 		/* Unlink controller state from context save list */
 		cs = spi->controller_state;
@@ -1080,19 +1081,6 @@ static void omap2_mcspi_cleanup(struct spi_device *spi)
 		kfree(cs);
 	}
 
-	if (spi->chip_select < spi->master->num_chipselect) {
-		mcspi_dma = &mcspi->dma_channels[spi->chip_select];
-
-		if (mcspi_dma->dma_rx) {
-			dma_release_channel(mcspi_dma->dma_rx);
-			mcspi_dma->dma_rx = NULL;
-		}
-		if (mcspi_dma->dma_tx) {
-			dma_release_channel(mcspi_dma->dma_tx);
-			mcspi_dma->dma_tx = NULL;
-		}
-	}
-
 	if (gpio_is_valid(spi->cs_gpio))
 		gpio_free(spi->cs_gpio);
 }
@@ -1303,6 +1291,9 @@ static bool omap2_mcspi_can_dma(struct spi_master *master,
 	if (spi_controller_is_slave(master))
 		return true;
 
+	master->dma_rx = mcspi_dma->dma_rx;
+	master->dma_tx = mcspi_dma->dma_tx;
+
 	return (xfer->len >= DMA_MIN_BYTES);
 }
 
@@ -1490,6 +1481,11 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 	for (i = 0; i < master->num_chipselect; i++) {
 		sprintf(mcspi->dma_channels[i].dma_rx_ch_name, "rx%d", i);
 		sprintf(mcspi->dma_channels[i].dma_tx_ch_name, "tx%d", i);
+
+		status = omap2_mcspi_request_dma(mcspi,
+						 &mcspi->dma_channels[i]);
+		if (status == -EPROBE_DEFER)
+			goto free_master;
 	}
 
 	status = platform_get_irq(pdev, 0);
@@ -1527,6 +1523,7 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 	pm_runtime_put_sync(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 free_master:
+	omap2_mcspi_release_dma(master);
 	spi_master_put(master);
 	return status;
 }
@@ -1536,6 +1533,8 @@ static int omap2_mcspi_remove(struct platform_device *pdev)
 	struct spi_master *master = platform_get_drvdata(pdev);
 	struct omap2_mcspi *mcspi = spi_master_get_devdata(master);
 
+	omap2_mcspi_release_dma(master);
+
 	pm_runtime_dont_use_autosuspend(mcspi->dev);
 	pm_runtime_put_sync(mcspi->dev);
 	pm_runtime_disable(&pdev->dev);
-- 
2.20.1

Applied "spi: spi-omap2-mcspi: Handle DMA size restriction on AM65x" to the spi tree

[Mark Brown]

The patch

   spi: spi-omap2-mcspi: Handle DMA size restriction on AM65x

has been applied to the spi tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-5.6

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 e4e8276a4f652be2c7bb783a0155d4adb85f5d7d Mon Sep 17 00:00:00 2001
From: Vignesh Raghavendra <vigneshr@ti.com>
Date: Tue, 4 Feb 2020 18:18:15 +0530
Subject: [PATCH] spi: spi-omap2-mcspi: Handle DMA size restriction on AM65x

On AM654, McSPI can only support 4K - 1 bytes per transfer when DMA is
enabled. Therefore populate master->max_transfer_size callback to
inform client drivers of this restriction when DMA channels are
available.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200204124816.16735-2-vigneshr@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-omap2-mcspi.c                 | 26 +++++++++++++++++++
 include/linux/platform_data/spi-omap2-mcspi.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 7e2292c11d12..e9bc9cf984d6 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -130,6 +130,7 @@ struct omap2_mcspi {
 	int			fifo_depth;
 	bool			slave_aborted;
 	unsigned int		pin_dir:1;
+	size_t			max_xfer_len;
 };
 
 struct omap2_mcspi_cs {
@@ -1305,6 +1306,18 @@ static bool omap2_mcspi_can_dma(struct spi_master *master,
 	return (xfer->len >= DMA_MIN_BYTES);
 }
 
+static size_t omap2_mcspi_max_xfer_size(struct spi_device *spi)
+{
+	struct omap2_mcspi *mcspi = spi_master_get_devdata(spi->master);
+	struct omap2_mcspi_dma *mcspi_dma =
+		&mcspi->dma_channels[spi->chip_select];
+
+	if (mcspi->max_xfer_len && mcspi_dma->dma_rx)
+		return mcspi->max_xfer_len;
+
+	return SIZE_MAX;
+}
+
 static int omap2_mcspi_controller_setup(struct omap2_mcspi *mcspi)
 {
 	struct spi_master	*master = mcspi->master;
@@ -1373,6 +1386,11 @@ static struct omap2_mcspi_platform_config omap4_pdata = {
 	.regs_offset = OMAP4_MCSPI_REG_OFFSET,
 };
 
+static struct omap2_mcspi_platform_config am654_pdata = {
+	.regs_offset = OMAP4_MCSPI_REG_OFFSET,
+	.max_xfer_len = SZ_4K - 1,
+};
+
 static const struct of_device_id omap_mcspi_of_match[] = {
 	{
 		.compatible = "ti,omap2-mcspi",
@@ -1382,6 +1400,10 @@ static const struct of_device_id omap_mcspi_of_match[] = {
 		.compatible = "ti,omap4-mcspi",
 		.data = &omap4_pdata,
 	},
+	{
+		.compatible = "ti,am654-mcspi",
+		.data = &am654_pdata,
+	},
 	{ },
 };
 MODULE_DEVICE_TABLE(of, omap_mcspi_of_match);
@@ -1439,6 +1461,10 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 		mcspi->pin_dir = pdata->pin_dir;
 	}
 	regs_offset = pdata->regs_offset;
+	if (pdata->max_xfer_len) {
+		mcspi->max_xfer_len = pdata->max_xfer_len;
+		master->max_transfer_size = omap2_mcspi_max_xfer_size;
+	}
 
 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	mcspi->base = devm_ioremap_resource(&pdev->dev, r);
diff --git a/include/linux/platform_data/spi-omap2-mcspi.h b/include/linux/platform_data/spi-omap2-mcspi.h
index 0bf9fddb8306..3b400b1919a9 100644
--- a/include/linux/platform_data/spi-omap2-mcspi.h
+++ b/include/linux/platform_data/spi-omap2-mcspi.h
@@ -11,6 +11,7 @@ struct omap2_mcspi_platform_config {
 	unsigned short	num_cs;
 	unsigned int regs_offset;
 	unsigned int pin_dir:1;
+	size_t max_xfer_len;
 };
 
 struct omap2_mcspi_device_config {
-- 
2.20.1