From: Ned Forrester <[EMAIL PROTECTED]>
Applies to kernel 2.6.25-rc1
Fixes a sequencing bug in spi driver pxa2xx_spi.c in which the chip
select for a transfer may be asserted before the transmission mode is
set on the interface. As a result of this bug, the pins of the
interface can make extra transitions after chip select is set and
before the intended clock/data signals begin. This only occurs on the
first transfer following a change in transmission mode. The fix
assures that all modes are set on the interface before asserting chip
select.
This bug was introduced in a patch merged on 2006/12/10, kernel 2.6.20.
The patch defines an additional bit in:
include/asm-arm/arch-pxa/regs-ssp.h
for 2.6.25 and newer kernels
but this addition must be made in:
include/asm-arm/arch-pxa/pxa-regs.h
for kernels between 2.6.20 and 2.6.24, inclusive
Signed-off-by: Ned Forrester <[EMAIL PROTECTED]>
---
drivers/spi/pxa2xx_spi.c | 41 +++++++++++++++++---------
include/asm-arm/arch-pxa/regs-ssp.h | 1
2 files changed, 28 insertions(+), 14 deletions(-)
diff -Nurp linux-2.6.25-rc1/drivers/spi/pxa2xx_spi.c
linux-2.6.25-rc1_cs_patch/drivers/spi/pxa2xx_spi.c
--- linux-2.6.25-rc1/drivers/spi/pxa2xx_spi.c 2008-02-12 21:52:35.000000000
+0000
+++ linux-2.6.25-rc1_cs_patch/drivers/spi/pxa2xx_spi.c 2008-02-20
23:34:29.000000000 +0000
@@ -51,13 +51,19 @@ MODULE_LICENSE("GPL");
#define RESET_DMA_CHANNEL (DCSR_NODESC | DMA_INT_MASK)
#define IS_DMA_ALIGNED(x) (((u32)(x)&0x07)==0)
-/* for testing SSCR1 changes that require SSP restart, basically
- * everything except the service and interrupt enables */
-#define SSCR1_CHANGE_MASK (SSCR1_TTELP | SSCR1_TTE | SSCR1_EBCEI | SSCR1_SCFR \
+/*
+ * for testing SSCR1 changes that require SSP restart, basically
+ * everything except the service and interrupt enables, the pxa270 developer
+ * manual says only SSCR1_SCFR, SSCR1_SPH, SSCR1_SPO need to be in this
+ * list, but the PXA255 dev man says all bits without really meaning the
+ * service and interrupt enables
+ */
+#define SSCR1_CHANGE_MASK (SSCR1_TTELP | SSCR1_TTE | SSCR1_SCFR \
| SSCR1_ECRA | SSCR1_ECRB | SSCR1_SCLKDIR \
- | SSCR1_RWOT | SSCR1_TRAIL | SSCR1_PINTE \
- | SSCR1_STRF | SSCR1_EFWR |SSCR1_RFT \
- | SSCR1_TFT | SSCR1_SPH | SSCR1_SPO | SSCR1_LBM)
+ | SSCR1_SFRMDIR | SSCR1_RWOT | SSCR1_TRAIL \
+ | SSCR1_IFS | SSCR1_STRF | SSCR1_EFWR \
+ | SSCR1_RFT | SSCR1_TFT | SSCR1_MWDS \
+ | SSCR1_SPH | SSCR1_SPO | SSCR1_LBM)
#define DEFINE_SSP_REG(reg, off) \
static inline u32 read_##reg(void *p) { return __raw_readl(p + (off)); } \
@@ -973,9 +979,6 @@ static void pump_transfers(unsigned long
if (drv_data->ssp_type == PXA25x_SSP)
DCMD(drv_data->tx_channel) |= DCMD_ENDIRQEN;
- /* Fix me, need to handle cs polarity */
- drv_data->cs_control(PXA2XX_CS_ASSERT);
-
/* Clear status and start DMA engine */
cr1 = chip->cr1 | dma_thresh | drv_data->dma_cr1;
write_SSSR(drv_data->clear_sr, reg);
@@ -985,9 +988,6 @@ static void pump_transfers(unsigned long
/* Ensure we have the correct interrupt handler */
drv_data->transfer_handler = interrupt_transfer;
- /* Fix me, need to handle cs polarity */
- drv_data->cs_control(PXA2XX_CS_ASSERT);
-
/* Clear status */
cr1 = chip->cr1 | chip->threshold | drv_data->int_cr1;
write_SSSR(drv_data->clear_sr, reg);
@@ -998,16 +998,29 @@ static void pump_transfers(unsigned long
|| (read_SSCR1(reg) & SSCR1_CHANGE_MASK) !=
(cr1 & SSCR1_CHANGE_MASK)) {
+ /* stop the SSP, and update the other bits */
write_SSCR0(cr0 & ~SSCR0_SSE, reg);
if (drv_data->ssp_type != PXA25x_SSP)
write_SSTO(chip->timeout, reg);
- write_SSCR1(cr1, reg);
+ /* first set CR1 without interrupt and service enables */
+ write_SSCR1(cr1 & SSCR1_CHANGE_MASK, reg);
+ /* restart the SSP */
write_SSCR0(cr0, reg);
+
} else {
if (drv_data->ssp_type != PXA25x_SSP)
write_SSTO(chip->timeout, reg);
- write_SSCR1(cr1, reg);
}
+
+ /* FIXME, need to handle cs polarity,
+ * this driver uses struct pxa2xx_spi_chip.cs_control to
+ * specify a CS handling function, and it ignores most
+ * struct spi_device.mode[s], including SPI_CS_HIGH */
+ drv_data->cs_control(PXA2XX_CS_ASSERT);
+
+ /* after chip select, release the data by enabling service
+ * requests and interrupts, without changing any mode bits */
+ write_SSCR1(cr1, reg);
}
static void pump_messages(struct work_struct *work)
diff -Nurp linux-2.6.25-rc1/include/asm-arm/arch-pxa/regs-ssp.h
linux-2.6.25-rc1_cs_patch/include/asm-arm/arch-pxa/regs-ssp.h
--- linux-2.6.25-rc1/include/asm-arm/arch-pxa/regs-ssp.h 2008-02-15
19:41:37.000000000 +0000
+++ linux-2.6.25-rc1_cs_patch/include/asm-arm/arch-pxa/regs-ssp.h
2008-02-15 19:47:40.000000000 +0000
@@ -85,6 +85,7 @@
#define SSCR1_RSRE (1 << 20) /* Receive Service Request
Enable */
#define SSCR1_TINTE (1 << 19) /* Receiver Time-out Interrupt
enable */
#define SSCR1_PINTE (1 << 18) /* Peripheral Trailing Byte
Interupt Enable */
+#define SSCR1_IFS (1 << 16) /* Invert Frame Signal */
#define SSCR1_STRF (1 << 15) /* Select FIFO or EFWR */
#define SSCR1_EFWR (1 << 14) /* Enable FIFO Write/Read */
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