linux-kernel - [PATCH] Revert "spi: omap2-mcspi: Set FIFO DMA trigger level to word length"

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Date:   Sun, 13 Jan 2019 14:49:05 -0600
From:   David Lechner <david@...hnology.com>
To:     linux-spi@...r.kernel.org
Cc:     David Lechner <david@...hnology.com>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
        Vignesh R <vigneshr@...com>
Subject: [PATCH] Revert "spi: omap2-mcspi: Set FIFO DMA trigger level to word length"

This reverts commit b682cffa3ac6d9d9e16e9b413c45caee3b391fab.

That commit breaks displays using tinydrm drivers, such as ili9225.

It causes corruption in the image that is displayed (it looks like only
1/2 of the framebuffer data is sent, the other half of the display
remains blank.)

The following error appears multiple times:

    ili9225 spi1.0: EOW timed out

Eventually, the system locks up without any additional errors.

Cc: Vignesh R <vigneshr@...com>
Signed-off-by: David Lechner <david@...hnology.com>
---
 drivers/spi/spi-omap2-mcspi.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 2fd8881fcd65..5a3854ff2e08 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -306,7 +306,7 @@ static void omap2_mcspi_set_fifo(const struct spi_device *spi,
 	struct omap2_mcspi_cs *cs = spi->controller_state;
 	struct omap2_mcspi *mcspi;
 	unsigned int wcnt;
-	int max_fifo_depth, bytes_per_word;
+	int max_fifo_depth, fifo_depth, bytes_per_word;
 	u32 chconf, xferlevel;
 
 	mcspi = spi_master_get_devdata(master);
@@ -322,6 +322,10 @@ static void omap2_mcspi_set_fifo(const struct spi_device *spi,
 		else
 			max_fifo_depth = OMAP2_MCSPI_MAX_FIFODEPTH;
 
+		fifo_depth = gcd(t->len, max_fifo_depth);
+		if (fifo_depth < 2 || fifo_depth % bytes_per_word != 0)
+			goto disable_fifo;
+
 		wcnt = t->len / bytes_per_word;
 		if (wcnt > OMAP2_MCSPI_MAX_FIFOWCNT)
 			goto disable_fifo;
@@ -329,17 +333,16 @@ static void omap2_mcspi_set_fifo(const struct spi_device *spi,
 		xferlevel = wcnt << 16;
 		if (t->rx_buf != NULL) {
 			chconf |= OMAP2_MCSPI_CHCONF_FFER;
-			xferlevel |= (bytes_per_word - 1) << 8;
+			xferlevel |= (fifo_depth - 1) << 8;
 		}
-
 		if (t->tx_buf != NULL) {
 			chconf |= OMAP2_MCSPI_CHCONF_FFET;
-			xferlevel |= bytes_per_word - 1;
+			xferlevel |= fifo_depth - 1;
 		}
 
 		mcspi_write_reg(master, OMAP2_MCSPI_XFERLEVEL, xferlevel);
 		mcspi_write_chconf0(spi, chconf);
-		mcspi->fifo_depth = max_fifo_depth;
+		mcspi->fifo_depth = fifo_depth;
 
 		return;
 	}
@@ -598,6 +601,7 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
 	struct dma_slave_config	cfg;
 	enum dma_slave_buswidth width;
 	unsigned es;
+	u32			burst;
 	void __iomem		*chstat_reg;
 	void __iomem            *irqstat_reg;
 	int			wait_res;
@@ -617,14 +621,22 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
 	}
 
 	count = xfer->len;
+	burst = 1;
+
+	if (mcspi->fifo_depth > 0) {
+		if (count > mcspi->fifo_depth)
+			burst = mcspi->fifo_depth / es;
+		else
+			burst = count / es;
+	}
 
 	memset(&cfg, 0, sizeof(cfg));
 	cfg.src_addr = cs->phys + OMAP2_MCSPI_RX0;
 	cfg.dst_addr = cs->phys + OMAP2_MCSPI_TX0;
 	cfg.src_addr_width = width;
 	cfg.dst_addr_width = width;
-	cfg.src_maxburst = es;
-	cfg.dst_maxburst = es;
+	cfg.src_maxburst = burst;
+	cfg.dst_maxburst = burst;
 
 	rx = xfer->rx_buf;
 	tx = xfer->tx_buf;
-- 
2.17.1