pxa2xx_spi: fix chip_info defaults and documentation.

Make the chip info structure data optional by providing reasonable
defaults.  Improve corresponding documentation, and highlight the drawback
of not providing explicit chipselect control.

DMA can determine appropriate dma_burst_size and thresholds automatically
so use DMA even if dma_burst_size is not specified.

Signed-off-by: Vernon Sauder <VernonInHand@gmail.com>
Reviewed-by: Ned Forrester <nforrester@whoi.edu>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 19 deletions

diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
index 59ae3ed16658..dae87b1a4c6e 100644
--- a/drivers/spi/pxa2xx_spi.c
+++ b/drivers/spi/pxa2xx_spi.c
@@ -47,6 +47,10 @@ MODULE_ALIAS("platform:pxa2xx-spi");
 
 #define MAX_BUSES 3
 
+#define RX_THRESH_DFLT  8
+#define TX_THRESH_DFLT  8
+#define TIMOUT_DFLT             1000
+
 #define DMA_INT_MASK            (DCSR_ENDINTR | DCSR_STARTINTR | DCSR_BUSERR)
 #define RESET_DMA_CHANNEL       (DCSR_NODESC | DMA_INT_MASK)
 #define IS_DMA_ALIGNED(x)       ((((u32)(x)) & 0x07) == 0)
@@ -1171,6 +1175,8 @@ static int setup(struct spi_device *spi)
         struct driver_data *drv_data = spi_master_get_devdata(spi->master);
         struct ssp_device *ssp = drv_data->ssp;
         unsigned int clk_div;
+        uint tx_thres = TX_THRESH_DFLT;
+        uint rx_thres = RX_THRESH_DFLT;
 
         if (!spi->bits_per_word)
                 spi->bits_per_word = 8;
@@ -1209,8 +1215,7 @@ static int setup(struct spi_device *spi)
 
                 chip->cs_control = null_cs_control;
                 chip->enable_dma = 0;
-                chip->timeout = 1000;
-                chip->threshold = SSCR1_RxTresh(1) | SSCR1_TxTresh(1);
+                chip->timeout = TIMOUT_DFLT;
                 chip->dma_burst_size = drv_data->master_info->enable_dma ?
                                         DCMD_BURST8 : 0;
         }
@@ -1224,22 +1229,21 @@ static int setup(struct spi_device *spi)
         if (chip_info) {
                 if (chip_info->cs_control)
                         chip->cs_control = chip_info->cs_control;
-
-                chip->timeout = chip_info->timeout;
-
-                chip->threshold = (SSCR1_RxTresh(chip_info->rx_threshold) &
-                                                                SSCR1_RFT) |
-                                (SSCR1_TxTresh(chip_info->tx_threshold) &
-                                                                SSCR1_TFT);
-
-                chip->enable_dma = chip_info->dma_burst_size != 0
-                                        && drv_data->master_info->enable_dma;
+                if (chip_info->timeout)
+                        chip->timeout = chip_info->timeout;
+                if (chip_info->tx_threshold)
+                        tx_thres = chip_info->tx_threshold;
+                if (chip_info->rx_threshold)
+                        rx_thres = chip_info->rx_threshold;
+                chip->enable_dma = drv_data->master_info->enable_dma;
                 chip->dma_threshold = 0;
-
                 if (chip_info->enable_loopback)
                         chip->cr1 = SSCR1_LBM;
         }
 
+        chip->threshold = (SSCR1_RxTresh(rx_thres) & SSCR1_RFT) |
+                        (SSCR1_TxTresh(tx_thres) & SSCR1_TFT);
+
         /* set dma burst and threshold outside of chip_info path so that if
          * chip_info goes away after setting chip->enable_dma, the
          * burst and threshold can still respond to changes in bits_per_word */
@@ -1268,17 +1272,19 @@ static int setup(struct spi_device *spi)
 
         /* NOTE:  PXA25x_SSP _could_ use external clocking ... */
         if (drv_data->ssp_type != PXA25x_SSP)
-                dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d\n",
+                dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d, %s\n",
                                 spi->bits_per_word,
                                 clk_get_rate(ssp->clk)
                                         / (1 + ((chip->cr0 & SSCR0_SCR) >> 8)),
-                                spi->mode & 0x3);
+                                spi->mode & 0x3,
+                                chip->enable_dma ? "DMA" : "PIO");
         else
-                dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d\n",
+                dev_dbg(&spi->dev, "%d bits/word, %ld Hz, mode %d, %s\n",
                                 spi->bits_per_word,
-                                clk_get_rate(ssp->clk)
+                                clk_get_rate(ssp->clk) / 2
                                         / (1 + ((chip->cr0 & SSCR0_SCR) >> 8)),
-                                spi->mode & 0x3);
+                                spi->mode & 0x3,
+                                chip->enable_dma ? "DMA" : "PIO");
 
         if (spi->bits_per_word <= 8) {
                 chip->n_bytes = 1;
@@ -1498,7 +1504,9 @@ static int __init pxa2xx_spi_probe(struct platform_device *pdev)
 
         /* Load default SSP configuration */
         write_SSCR0(0, drv_data->ioaddr);
-        write_SSCR1(SSCR1_RxTresh(4) | SSCR1_TxTresh(12), drv_data->ioaddr);
+        write_SSCR1(SSCR1_RxTresh(RX_THRESH_DFLT) |
+                                SSCR1_TxTresh(TX_THRESH_DFLT),
+                                drv_data->ioaddr);
         write_SSCR0(SSCR0_SerClkDiv(2)
                         | SSCR0_Motorola
                         | SSCR0_DataSize(8),