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Commit 2ff271bf authored by Alek Du's avatar Alek Du Committed by Grant Likely
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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: default avatarAlek Du <alek.du@intel.com>
Signed-off-by: default avatarFeng Tang <feng.tang@intel.com>
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent 8a33a373

drivers/spi/dw_spi.c

+48 −23
Original line number Diff line number Diff line
@@ -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);
@@ -175,12 +206,10 @@ 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;



	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)
@@ -188,20 +217,19 @@ static int dw_writer(struct dw_spi *dws) 
			else

				txw = *(u16 *)(dws->tx);

		}



		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))

		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.

	 */

	do {

		dw_writer(dws);

		dw_reader(dws);

		cpu_relax();

	} while (dws->rx_end > dws->rx);



	dw_spi_xfer_done(dws);

}