The patch titled
pxa2xx_spi: fix chip_info defaults and documentation.
has been added to the -mm tree. Its filename is
pxa2xx_spi-fix-chip_info-defaults-and-documentation.patch
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Subject: pxa2xx_spi: fix chip_info defaults and documentation.
From: Vernon Sauder <vernoninhand@xxxxxxxxx>
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@xxxxxxxxx>
Reviewed-by: Ned Forrester <nforrester@xxxxxxxx>
Signed-off-by: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/spi/pxa2xx | 34 +++++++++++++++++++---------
drivers/spi/pxa2xx_spi.c | 44 ++++++++++++++++++++++---------------
2 files changed, 50 insertions(+), 28 deletions(-)
diff -puN Documentation/spi/pxa2xx~pxa2xx_spi-fix-chip_info-defaults-and-documentation Documentation/spi/pxa2xx
--- a/Documentation/spi/pxa2xx~pxa2xx_spi-fix-chip_info-defaults-and-documentation
+++ a/Documentation/spi/pxa2xx
@@ -96,7 +96,7 @@ Each slave device attached to the PXA mu
information via the structure "pxa2xx_spi_chip" found in
"arch/arm/mach-pxa/include/mach/pxa2xx_spi.h". The pxa2xx_spi master controller driver
will uses the configuration whenever the driver communicates with the slave
-device.
+device. All fields are optional.
struct pxa2xx_spi_chip {
u8 tx_threshold;
@@ -112,14 +112,17 @@ used to configure the SSP hardware fifo.
performance of pxa2xx_spi driver and misconfiguration will result in rx
fifo overruns (especially in PIO mode transfers). Good default values are
- .tx_threshold = 12,
- .rx_threshold = 4,
+ .tx_threshold = 8,
+ .rx_threshold = 8,
+
+The range is 1 to 16 where zero indicates "use default".
The "pxa2xx_spi_chip.dma_burst_size" field is used to configure PXA2xx DMA
engine and is related the "spi_device.bits_per_word" field. Read and understand
the PXA2xx "Developer Manual" sections on the DMA controller and SSP Controllers
to determine the correct value. An SSP configured for byte-wide transfers would
-use a value of 8.
+use a value of 8. The driver will determine a reasonable default if
+dma_burst_size == 0.
The "pxa2xx_spi_chip.timeout" fields is used to efficiently handle
trailing bytes in the SSP receiver fifo. The correct value for this field is
@@ -137,7 +140,13 @@ function for asserting/deasserting a sla
NULL, the pxa2xx_spi master controller driver assumes that the SSP port is
configured to use SSPFRM instead.
-NSSP SALVE SAMPLE
+NOTE: the SPI driver cannot control the chip select if SSPFRM is used, so the
+chipselect is dropped after each spi_transfer. Most devices need chip select
+asserted around the complete message. Use SSPFRM as a GPIO (through cs_control)
+to accomodate these chips.
+
+
+NSSP SLAVE SAMPLE
-----------------
The pxa2xx_spi_chip structure is passed to the pxa2xx_spi driver in the
"spi_board_info.controller_data" field. Below is a sample configuration using
@@ -206,18 +215,21 @@ static void __init streetracer_init(void
DMA and PIO I/O Support
-----------------------
-The pxa2xx_spi driver support both DMA and interrupt driven PIO message
-transfers. The driver defaults to PIO mode and DMA transfers must enabled by
-setting the "enable_dma" flag in the "pxa2xx_spi_master" structure and
-ensuring that the "pxa2xx_spi_chip.dma_burst_size" field is non-zero. The DMA
-mode support both coherent and stream based DMA mappings.
+The pxa2xx_spi driver supports both DMA and interrupt driven PIO message
+transfers. The driver defaults to PIO mode and DMA transfers must be enabled
+by setting the "enable_dma" flag in the "pxa2xx_spi_master" structure. The DMA
+mode supports both coherent and stream based DMA mappings.
The following logic is used to determine the type of I/O to be used on
a per "spi_transfer" basis:
-if !enable_dma or dma_burst_size == 0 then
+if !enable_dma then
always use PIO transfers
+if spi_message.len > 8191 then
+ print "rate limited" warning
+ use PIO transfers
+
if spi_message.is_dma_mapped and rx_dma_buf != 0 and tx_dma_buf != 0 then
use coherent DMA mode
diff -puN drivers/spi/pxa2xx_spi.c~pxa2xx_spi-fix-chip_info-defaults-and-documentation drivers/spi/pxa2xx_spi.c
--- a/drivers/spi/pxa2xx_spi.c~pxa2xx_spi-fix-chip_info-defaults-and-documentation
+++ a/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) (((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;
}
@@ -1225,21 +1230,22 @@ static int setup(struct spi_device *spi)
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 +1274,19 @@ 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 +1506,9 @@ static int __init pxa2xx_spi_probe(struc
/* 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),
_
Patches currently in -mm which might be from vernoninhand@xxxxxxxxx are
pxa2xx_spi-chipselect-bugfixes.patch
pxa2xx_spi-dma-bugfixes.patch
spi-simplify-spi_write_then_read.patch
pxa2xx_spi-fix-chip_info-defaults-and-documentation.patch
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