spi: dw: program registers as soon as possible

This patch refactors the code in pump_transfers() to reprogram the registers
immediately when we have a new configuration data. The behaviour is slightly
modified:
 - chip is always disabled and reenabled
 - CTRL0 is always reprogrammed

This change allows to do a further refactoring and simplier conversion to use
SPI core DMA routines in the future.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw.c

@@ -409,6 +409,8 @@ static void pump_transfers(unsigned long data)
 	if (chip != dws->prev_chip)
 		cs_change = 1;
 
+	spi_enable_chip(dws, 0);
+
 	cr0 = chip->cr0;
 
 	/* Handle per transfer options for bpw and speed */
@@ -423,6 +425,8 @@ static void pump_transfers(unsigned long data)
 
 			chip->speed_hz = speed;
 			chip->clk_div = clk_div;
+
+			spi_set_clk(dws, chip->clk_div);
 		}
 	}
 	if (transfer->bits_per_word) {
@@ -451,44 +455,32 @@ static void pump_transfers(unsigned long data)
 		cr0 |= (chip->tmode << SPI_TMOD_OFFSET);
 	}
 
+	dw_writew(dws, DW_SPI_CTRL0, cr0);
+	spi_chip_sel(dws, spi, 1);
+
 	/* Check if current transfer is a DMA transaction */
 	dws->dma_mapped = map_dma_buffers(dws);
 
+	/* For poll mode just disable all interrupts */
+	spi_mask_intr(dws, 0xff);
+
 	/*
 	 * Interrupt mode
 	 * we only need set the TXEI IRQ, as TX/RX always happen syncronizely
 	 */
 	if (!dws->dma_mapped && !chip->poll_mode) {
 		txlevel = min_t(u16, dws->fifo_len / 2, dws->len / dws->n_bytes);
+		dw_writew(dws, DW_SPI_TXFLTR, txlevel);
 
+		/* Set the interrupt mask */
 		imask |= SPI_INT_TXEI | SPI_INT_TXOI |
 			 SPI_INT_RXUI | SPI_INT_RXOI;
+		spi_umask_intr(dws, imask);
+
 		dws->transfer_handler = interrupt_transfer;
 	}
 
-	/*
-	 * Reprogram registers only if
-	 *	1. chip select changes
-	 *	2. clk_div is changed
-	 *	3. control value changes
-	 */
-	if (dw_readw(dws, DW_SPI_CTRL0) != cr0 || cs_change || clk_div || imask) {
-		spi_enable_chip(dws, 0);
-
-		dw_writew(dws, DW_SPI_CTRL0, cr0);
-
-		spi_set_clk(dws, chip->clk_div);
-		spi_chip_sel(dws, spi, 1);
-
-		/* Set the interrupt mask, for poll mode just disable all int */
-		spi_mask_intr(dws, 0xff);
-		if (imask)
-			spi_umask_intr(dws, imask);
-		if (txlevel)
-			dw_writew(dws, DW_SPI_TXFLTR, txlevel);
-
-		spi_enable_chip(dws, 1);
-	}
+	spi_enable_chip(dws, 1);
 
 	if (cs_change)
 		dws->prev_chip = chip;