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From:   David Lechner <david@lechnology.com>
To:     linux-spi@vger.kernel.org
Cc:     David Lechner <david@lechnology.com>,
        Mark Brown <broonie@kernel.org>, linux-kernel@vger.kernel.org,
        Vignesh R <vigneshr@ti.com>
Subject: [PATCH] Revert "spi: omap2-mcspi: Set FIFO DMA trigger level to word length"
Date:   Sun, 13 Jan 2019 14:49:05 -0600
Message-Id: <20190113204905.29795-1-david@lechnology.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@ti.com>
Signed-off-by: David Lechner <david@lechnology.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