This patch is to avoid breaking some drivers, in my case the ADS7846
touchscreen one, which use 1 char messages.
If you put the dummy byte after the 1 char message, you get part of the
answer to the message in the rxbuf of the message, which is thrown away.
The solution is to put the dummy byte before the message, so that the
slave doesn't respond.
It also optimizes the interrupt handling, by using the alarm function of
the FIFO, to wait until the rx FIFO has received enough bytes, instead
of waiting until the tx FIFO is empty.
Signed-off-by: Matteo Fortini <m.fort...@selcomgroup.com>
---
drivers/spi/mpc512x_psc_spi.c | 50
+++++++++++++++++++++++-----------------
1 files changed, 29 insertions(+), 21 deletions(-)
diff --git a/drivers/spi/mpc512x_psc_spi.c b/drivers/spi/mpc512x_psc_spi.c
index 1fd7ad4..eace796 100644
--- a/drivers/spi/mpc512x_psc_spi.c
+++ b/drivers/spi/mpc512x_psc_spi.c
@@ -175,6 +175,7 @@ static int mpc512x_psc_spi_transfer_rxtx(struct
spi_device *spi,
u8 data;
size_t fifosz;
int rxcount;
+ int txcount;
/*
* The number of bytes that can be sent at a time
@@ -183,41 +184,49 @@ static int mpc512x_psc_spi_transfer_rxtx(struct
spi_device *spi,
fifosz = MPC512x_PSC_FIFO_SZ(in_be32(&fifo->txsz));
count = min(fifosz, len);
+ txcount = 0;
+ /*
+ * Insert a dummy byte before a message of len 1 to make it at
least 2 bytes long
+ * to be able to set EOF correctly
+ */
+ if (t->len == 1) {
+ out_8(&fifo->txdata_8, 0);
+ txcount++;
+ }
for (i = count; i > 0; i--) {
if (len == EOFBYTE || t->len == 1)
setbits32(&fifo->txcmd, MPC512x_PSC_FIFO_EOF);
data = tx_buf ? *tx_buf++ : 0;
out_8(&fifo->txdata_8, data);
- if (t->len == 1)
- out_8(&fifo->txdata_8, 0);
+ txcount++;
len--;
}
INIT_COMPLETION(mps->done);
- /* interrupt on tx fifo empty */
- out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
- out_be32(&fifo->tximr, MPC512x_PSC_FIFO_EMPTY);
-
- /* enable transmiter/receiver */
- out_8(&psc->command, MPC52xx_PSC_TX_ENABLE |
MPC52xx_PSC_RX_ENABLE);
+ /* Enable FIFO_ALARM interrupts for rx_fifo */
+ out_be32(&fifo->rxalarm, txcount);
+ out_be32(&fifo->rxisr, MPC512x_PSC_FIFO_ALARM);
+ out_be32(&fifo->rximr, MPC512x_PSC_FIFO_ALARM);
- wait_for_completion(&mps->done);
+ /* Disable tx_fifo interrupts */
+ out_be32(&fifo->txisr, 0xffffffff);
+ out_be32(&fifo->tximr, 0);
- mdelay(1);
+ out_8(&psc->command, MPC52xx_PSC_TX_ENABLE |
MPC52xx_PSC_RX_ENABLE);
- /* rx fifo should have count bytes in it */
- rxcount = in_be32(&fifo->rxcnt);
- if (rxcount != count)
- mdelay(1);
+ wait_for_completion (&mps->done);
rxcount = in_be32(&fifo->rxcnt);
- if (rxcount != count && t->len != 1)
+ if (rxcount != txcount)
printk(KERN_WARNING "expected %d bytes in rx fifo "
- "but got %d\n", count, rxcount);
-
+ "but got %d\n", txcount, rxcount);
rxcount = min(rxcount, count);
{
+ /* Throw away possible initial dummy byte */
+ if (t->len == 1) {
+ (void)in_8(&fifo->rxdata_8);
+ }
for (i = rxcount; i > 0; i--) {
data = in_8(&fifo->rxdata_8);
if (rx_buf)
@@ -418,10 +427,9 @@ static irqreturn_t mpc512x_psc_spi_isr(int irq,
void *dev_id)
struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;
/* clear interrupt and wake up the work queue */
- if (in_be32(&fifo->txisr)
- & in_be32(&fifo->tximr) & MPC512x_PSC_FIFO_EMPTY) {
- out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
- out_be32(&fifo->tximr, 0);
+ if (in_be32(&fifo->rxisr) & in_be32(&fifo->rximr) &
MPC512x_PSC_FIFO_ALARM) {
+ out_be32(&fifo->rxisr, MPC512x_PSC_FIFO_ALARM);
+ out_be32(&fifo->rximr, 0);
complete(&mps->done);
return IRQ_HANDLED;
}
--
1.5.4.3
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