Blackfin SPI driver: use cpu_relax() to replace continue in while busywait

Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c
index a85bcb3..0e33b5a 100644 (file)
--- a/drivers/spi/spi_bfin5xx.c
+++ b/drivers/spi/spi_bfin5xx.c
@@ -186,7 +186,7 @@ static int flush(struct driver_data *drv_data)
 
        /* wait for stop and clear stat */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF) && limit--)
-               continue;
+               cpu_relax();
 
        write_STAT(drv_data, BIT_STAT_CLR);
 
@@ -262,7 +262,7 @@ static void null_writer(struct driver_data *drv_data)
        while (drv_data->tx < drv_data->tx_end) {
                write_TDBR(drv_data, 0);
                while ((read_STAT(drv_data) & BIT_STAT_TXS))
-                       continue;
+                       cpu_relax();
                drv_data->tx += n_bytes;
        }
 }
@@ -274,7 +274,7 @@ static void null_reader(struct driver_data *drv_data)
 
        while (drv_data->rx < drv_data->rx_end) {
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                dummy_read(drv_data);
                drv_data->rx += n_bytes;
        }
@@ -287,12 +287,12 @@ static void u8_writer(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        while (drv_data->tx < drv_data->tx_end) {
                write_TDBR(drv_data, (*(u8 *) (drv_data->tx)));
                while (read_STAT(drv_data) & BIT_STAT_TXS)
-                       continue;
+                       cpu_relax();
                ++drv_data->tx;
        }
 }
@@ -303,14 +303,14 @@ static void u8_cs_chg_writer(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        while (drv_data->tx < drv_data->tx_end) {
                cs_active(drv_data, chip);
 
                write_TDBR(drv_data, (*(u8 *) (drv_data->tx)));
                while (read_STAT(drv_data) & BIT_STAT_TXS)
-                       continue;
+                       cpu_relax();
 
                cs_deactive(drv_data, chip);
 
@@ -325,7 +325,7 @@ static void u8_reader(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        /* clear TDBR buffer before read(else it will be shifted out) */
        write_TDBR(drv_data, 0xFFFF);
@@ -334,13 +334,13 @@ static void u8_reader(struct driver_data *drv_data)
 
        while (drv_data->rx < drv_data->rx_end - 1) {
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                *(u8 *) (drv_data->rx) = read_RDBR(drv_data);
                ++drv_data->rx;
        }
 
        while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-               continue;
+               cpu_relax();
        *(u8 *) (drv_data->rx) = read_SHAW(drv_data);
        ++drv_data->rx;
 }
@@ -351,7 +351,7 @@ static void u8_cs_chg_reader(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        /* clear TDBR buffer before read(else it will be shifted out) */
        write_TDBR(drv_data, 0xFFFF);
@@ -363,7 +363,7 @@ static void u8_cs_chg_reader(struct driver_data *drv_data)
                cs_deactive(drv_data, chip);
 
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                cs_active(drv_data, chip);
                *(u8 *) (drv_data->rx) = read_RDBR(drv_data);
                ++drv_data->rx;
@@ -371,7 +371,7 @@ static void u8_cs_chg_reader(struct driver_data *drv_data)
        cs_deactive(drv_data, chip);
 
        while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-               continue;
+               cpu_relax();
        *(u8 *) (drv_data->rx) = read_SHAW(drv_data);
        ++drv_data->rx;
 }
@@ -380,15 +380,15 @@ static void u8_duplex(struct driver_data *drv_data)
 {
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        /* in duplex mode, clk is triggered by writing of TDBR */
        while (drv_data->rx < drv_data->rx_end) {
                write_TDBR(drv_data, (*(u8 *) (drv_data->tx)));
                while (read_STAT(drv_data) & BIT_STAT_TXS)
-                       continue;
+                       cpu_relax();
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                *(u8 *) (drv_data->rx) = read_RDBR(drv_data);
                ++drv_data->rx;
                ++drv_data->tx;
@@ -401,16 +401,16 @@ static void u8_cs_chg_duplex(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        while (drv_data->rx < drv_data->rx_end) {
                cs_active(drv_data, chip);
 
                write_TDBR(drv_data, (*(u8 *) (drv_data->tx)));
                while (read_STAT(drv_data) & BIT_STAT_TXS)
-                       continue;
+                       cpu_relax();
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                *(u8 *) (drv_data->rx) = read_RDBR(drv_data);
 
                cs_deactive(drv_data, chip);
@@ -427,12 +427,12 @@ static void u16_writer(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        while (drv_data->tx < drv_data->tx_end) {
                write_TDBR(drv_data, (*(u16 *) (drv_data->tx)));
                while ((read_STAT(drv_data) & BIT_STAT_TXS))
-                       continue;
+                       cpu_relax();
                drv_data->tx += 2;
        }
 }
@@ -443,14 +443,14 @@ static void u16_cs_chg_writer(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        while (drv_data->tx < drv_data->tx_end) {
                cs_active(drv_data, chip);
 
                write_TDBR(drv_data, (*(u16 *) (drv_data->tx)));
                while ((read_STAT(drv_data) & BIT_STAT_TXS))
-                       continue;
+                       cpu_relax();
 
                cs_deactive(drv_data, chip);
 
@@ -465,7 +465,7 @@ static void u16_reader(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        /* clear TDBR buffer before read(else it will be shifted out) */
        write_TDBR(drv_data, 0xFFFF);
@@ -474,13 +474,13 @@ static void u16_reader(struct driver_data *drv_data)
 
        while (drv_data->rx < (drv_data->rx_end - 2)) {
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                *(u16 *) (drv_data->rx) = read_RDBR(drv_data);
                drv_data->rx += 2;
        }
 
        while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-               continue;
+               cpu_relax();
        *(u16 *) (drv_data->rx) = read_SHAW(drv_data);
        drv_data->rx += 2;
 }
@@ -491,7 +491,7 @@ static void u16_cs_chg_reader(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        /* clear TDBR buffer before read(else it will be shifted out) */
        write_TDBR(drv_data, 0xFFFF);
@@ -503,7 +503,7 @@ static void u16_cs_chg_reader(struct driver_data *drv_data)
                cs_deactive(drv_data, chip);
 
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                cs_active(drv_data, chip);
                *(u16 *) (drv_data->rx) = read_RDBR(drv_data);
                drv_data->rx += 2;
@@ -511,7 +511,7 @@ static void u16_cs_chg_reader(struct driver_data *drv_data)
        cs_deactive(drv_data, chip);
 
        while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-               continue;
+               cpu_relax();
        *(u16 *) (drv_data->rx) = read_SHAW(drv_data);
        drv_data->rx += 2;
 }
@@ -520,15 +520,15 @@ static void u16_duplex(struct driver_data *drv_data)
 {
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        /* in duplex mode, clk is triggered by writing of TDBR */
        while (drv_data->tx < drv_data->tx_end) {
                write_TDBR(drv_data, (*(u16 *) (drv_data->tx)));
                while (read_STAT(drv_data) & BIT_STAT_TXS)
-                       continue;
+                       cpu_relax();
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                *(u16 *) (drv_data->rx) = read_RDBR(drv_data);
                drv_data->rx += 2;
                drv_data->tx += 2;
@@ -541,16 +541,16 @@ static void u16_cs_chg_duplex(struct driver_data *drv_data)
 
        /* poll for SPI completion before start */
        while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-               continue;
+               cpu_relax();
 
        while (drv_data->tx < drv_data->tx_end) {
                cs_active(drv_data, chip);
 
                write_TDBR(drv_data, (*(u16 *) (drv_data->tx)));
                while (read_STAT(drv_data) & BIT_STAT_TXS)
-                       continue;
+                       cpu_relax();
                while (!(read_STAT(drv_data) & BIT_STAT_RXS))
-                       continue;
+                       cpu_relax();
                *(u16 *) (drv_data->rx) = read_RDBR(drv_data);
 
                cs_deactive(drv_data, chip);
@@ -624,7 +624,7 @@ static irqreturn_t dma_irq_handler(int irq, void *dev_id)
 
        /* Wait for DMA to complete */
        while (get_dma_curr_irqstat(drv_data->dma_channel) & DMA_RUN)
-               continue;
+               cpu_relax();
 
        /*
         * wait for the last transaction shifted out.  HRM states:
@@ -635,11 +635,11 @@ static irqreturn_t dma_irq_handler(int irq, void *dev_id)
        if (drv_data->tx != NULL) {
                while ((read_STAT(drv_data) & TXS) ||
                       (read_STAT(drv_data) & TXS))
-                       continue;
+                       cpu_relax();
        }
 
        while (!(read_STAT(drv_data) & SPIF))
-               continue;
+               cpu_relax();
 
        msg->actual_length += drv_data->len_in_bytes;
 
@@ -783,7 +783,7 @@ static void pump_transfers(unsigned long data)
 
                /* poll for SPI completion before start */
                while (!(read_STAT(drv_data) & BIT_STAT_SPIF))
-                       continue;
+                       cpu_relax();
 
                /* dirty hack for autobuffer DMA mode */
                if (drv_data->tx_dma == 0xFFFF) {