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spi/dw_spi: change poll mode transfer from byte ops to batch ops 

Current poll transfer will read/write one word, then wait till the
hw is non-busy, it's not efficient. This patch will try to read/write
as many words as permitted by hardware FIFO depth.

Signed-off-by: Alek Du <alek.du@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Alek Du 2011-03-30 23:09:54 +08:00 committed by Grant Likely
parent 8a33a373e5
commit 2ff271bf65
1 changed files with 48 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

71
drivers/spi/dw_spi.c
View File

@ -160,6 +160,37 @@ static inline void mrst_spi_debugfs_remove(struct dw_spi *dws)
}
#endif /* CONFIG_DEBUG_FS */
/* Return the max entries we can fill into tx fifo */
static inline u32 tx_max(struct dw_spi *dws)
{
u32 tx_left, tx_room, rxtx_gap;
tx_left = (dws->tx_end - dws->tx) / dws->n_bytes;
tx_room = dws->fifo_len - dw_readw(dws, txflr);
/*
* Another concern is about the tx/rx mismatch, we
* though to use (dws->fifo_len - rxflr - txflr) as
* one maximum value for tx, but it doesn't cover the
* data which is out of tx/rx fifo and inside the
* shift registers. So a control from sw point of
* view is taken.
*/
rxtx_gap = ((dws->rx_end - dws->rx) - (dws->tx_end - dws->tx))
/ dws->n_bytes;
return min3(tx_left, tx_room, (u32) (dws->fifo_len - rxtx_gap));
}
/* Return the max entries we should read out of rx fifo */
static inline u32 rx_max(struct dw_spi *dws)
{
u32 rx_left = (dws->rx_end - dws->rx) / dws->n_bytes;
return min(rx_left, (u32)dw_readw(dws, rxflr));
}
static void wait_till_not_busy(struct dw_spi *dws)
{
unsigned long end = jiffies + 1 + usecs_to_jiffies(5000);
@ -175,33 +206,30 @@ static void wait_till_not_busy(struct dw_spi *dws)
static int dw_writer(struct dw_spi *dws)
{
u32 max = tx_max(dws);
u16 txw = 0;
if (!(dw_readw(dws, sr) & SR_TF_NOT_FULL)
|| (dws->tx == dws->tx_end))
return 0;
/* Set the tx word if the transfer's original "tx" is not null */
if (dws->tx_end - dws->len) {
if (dws->n_bytes == 1)
txw = *(u8 *)(dws->tx);
else
txw = *(u16 *)(dws->tx);
while (max--) {
/* Set the tx word if the transfer's original "tx" is not null */
if (dws->tx_end - dws->len) {
if (dws->n_bytes == 1)
txw = *(u8 *)(dws->tx);
else
txw = *(u16 *)(dws->tx);
}
dw_writew(dws, dr, txw);
dws->tx += dws->n_bytes;
}
dw_writew(dws, dr, txw);
dws->tx += dws->n_bytes;
wait_till_not_busy(dws);
return 1;
}
static int dw_reader(struct dw_spi *dws)
{
u32 max = rx_max(dws);
u16 rxw;
while ((dw_readw(dws, sr) & SR_RF_NOT_EMPT)
&& (dws->rx < dws->rx_end)) {
while (max--) {
rxw = dw_readw(dws, dr);
/* Care rx only if the transfer's original "rx" is not null */
if (dws->rx_end - dws->len) {
@ -213,7 +241,6 @@ static int dw_reader(struct dw_spi *dws)
dws->rx += dws->n_bytes;
}
wait_till_not_busy(dws);
return dws->rx == dws->rx_end;
}
@ -368,13 +395,11 @@ static irqreturn_t dw_spi_irq(int irq, void *dev_id)
/* Must be called inside pump_transfers() */
static void poll_transfer(struct dw_spi *dws)
{
while (dw_writer(dws))
do {
dw_writer(dws);
dw_reader(dws);
/*
* There is a possibility that the last word of a transaction
* will be lost if data is not ready. Re-read to solve this issue.
*/
dw_reader(dws);
cpu_relax();
} while (dws->rx_end > dws->rx);
dw_spi_xfer_done(dws);
}