linux-kernel - [PATCH] spi: omap2-mcspi: In case of dma errors fall back to pio

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Date:	Wed, 25 Jul 2012 11:50:29 +0530
From:	Shubhrajyoti D <shubhrajyoti@...com>
To:	<spi-devel-general@...ts.sourceforge.net>
CC:	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Shubhrajyoti D <shubhrajyoti@...com>
Subject: [PATCH] spi: omap2-mcspi: In case of dma errors fall back to pio

In case there are dma errors currently the driver exits.
Make the spi driver fall back to pio mode in case of dma errors.

If the DMA engine is not selected the driver
exits.This patch makes the spi fall back to pio in that case.

Also adds a field dma_unusable to struct omap2_mcspi.
 
Signed-off-by: Shubhrajyoti D <shubhrajyoti@...com>
---
 drivers/spi/spi-omap2-mcspi.c |   21 +++++++++++++--------
 1 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index bc47781..f243a39 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -129,6 +129,7 @@ struct omap2_mcspi {
 	struct omap2_mcspi_dma	*dma_channels;
 	struct device		*dev;
 	struct omap2_mcspi_regs ctx;
+	int dma_unusable;
 };
 
 struct omap2_mcspi_cs {
@@ -845,7 +846,7 @@ 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 < 0)
-			return ret;
+			mcspi->dma_unusable = 1;
 	}
 
 	ret = omap2_mcspi_enable_clocks(mcspi);
@@ -956,7 +957,8 @@ static void omap2_mcspi_work(struct omap2_mcspi *mcspi, struct spi_message *m)
 				__raw_writel(0, cs->base
 						+ OMAP2_MCSPI_TX0);
 
-			if (m->is_dma_mapped || t->len >= DMA_MIN_BYTES)
+			if (!mcspi->dma_unusable && (m->is_dma_mapped ||
+						t->len >= DMA_MIN_BYTES))
 				count = omap2_mcspi_txrx_dma(spi, t);
 			else
 				count = omap2_mcspi_txrx_pio(spi, t);
@@ -1030,7 +1032,8 @@ static int omap2_mcspi_transfer_one_message(struct spi_master *master,
 			return -EINVAL;
 		}
 
-		if (m->is_dma_mapped || len < DMA_MIN_BYTES)
+		if (mcspi->dma_unusable || m->is_dma_mapped ||
+					len < DMA_MIN_BYTES)
 			continue;
 
 		if (tx_buf != NULL) {
@@ -1054,6 +1057,7 @@ static int omap2_mcspi_transfer_one_message(struct spi_master *master,
 				return -EINVAL;
 			}
 		}
+
 	}
 
 	omap2_mcspi_work(mcspi, m);
@@ -1216,9 +1220,12 @@ static int __devinit omap2_mcspi_probe(struct platform_device *pdev)
 		mcspi->dma_channels[i].dma_tx_sync_dev = dma_res->start;
 	}
 
-	if (status < 0)
-		goto dma_chnl_free;
-
+	if (status < 0) {
+		dev_err(&pdev->dev, "cannot get DMA channel switching to pio\n");
+		mcspi->dma_unusable = 1;
+		status = 0;
+		kfree(mcspi->dma_channels);
+	}
 	pm_runtime_use_autosuspend(&pdev->dev);
 	pm_runtime_set_autosuspend_delay(&pdev->dev, SPI_AUTOSUSPEND_TIMEOUT);
 	pm_runtime_enable(&pdev->dev);
@@ -1229,14 +1236,12 @@ static int __devinit omap2_mcspi_probe(struct platform_device *pdev)
 	status = spi_register_master(master);
 	if (status < 0)
 		goto err_spi_register;
-
 	return status;
 
 err_spi_register:
 	spi_master_put(master);
 disable_pm:
 	pm_runtime_disable(&pdev->dev);
-dma_chnl_free:
 	kfree(mcspi->dma_channels);
 free_master:
 	kfree(master);
-- 
1.7.5.4

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