spi: stm32: Revert change that enabled controller before asserting CS

On stm32mp157 enabling the controller before asserting CS makes the
hardware trigger spurious interrupts in a tight loop and the transfers
fail. Revert the commit that swapped the order of enable and CS. This
reintroduces the problem that swapping was supposed to fix, which
however is less grave.

Reported-by: Leonard Göhrs <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/
Fixes: 52b62e7 ("spi: stm32: enable controller before asserting CS")
Signed-off-by: Uwe Kleine-König <[email protected]>
Link: https://msgid.link/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: Uwe Kleine-König

drivers/spi/spi-stm32.c

@@ -1016,8 +1016,10 @@ static irqreturn_t stm32fx_spi_irq_event(int irq, void *dev_id)
 static irqreturn_t stm32fx_spi_irq_thread(int irq, void *dev_id)
 {
 	struct spi_controller *ctrl = dev_id;
+	struct stm32_spi *spi = spi_controller_get_devdata(ctrl);
 
 	spi_finalize_current_transfer(ctrl);
+	stm32fx_spi_disable(spi);
 
 	return IRQ_HANDLED;
 }
@@ -1185,8 +1187,6 @@ static int stm32_spi_prepare_msg(struct spi_controller *ctrl,
 			 ~clrb) | setb,
 			spi->base + spi->cfg->regs->cpol.reg);
 
-	stm32_spi_enable(spi);
-
 	spin_unlock_irqrestore(&spi->lock, flags);
 
 	return 0;
@@ -1204,6 +1204,7 @@ static void stm32fx_spi_dma_tx_cb(void *data)
 
 	if (spi->cur_comm == SPI_SIMPLEX_TX || spi->cur_comm == SPI_3WIRE_TX) {
 		spi_finalize_current_transfer(spi->ctrl);
+		stm32fx_spi_disable(spi);
 	}
 }
 
@@ -1218,6 +1219,7 @@ static void stm32_spi_dma_rx_cb(void *data)
 	struct stm32_spi *spi = data;
 
 	spi_finalize_current_transfer(spi->ctrl);
+	spi->cfg->disable(spi);
 }
 
 /**
@@ -1305,6 +1307,8 @@ static int stm32fx_spi_transfer_one_irq(struct stm32_spi *spi)
 
 	stm32_spi_set_bits(spi, STM32FX_SPI_CR2, cr2);
 
+	stm32_spi_enable(spi);
+
 	/* starting data transfer when buffer is loaded */
 	if (spi->tx_buf)
 		spi->cfg->write_tx(spi);
@@ -1341,6 +1345,8 @@ static int stm32h7_spi_transfer_one_irq(struct stm32_spi *spi)
 
 	spin_lock_irqsave(&spi->lock, flags);
 
+	stm32_spi_enable(spi);
+
 	/* Be sure to have data in fifo before starting data transfer */
 	if (spi->tx_buf)
 		stm32h7_spi_write_txfifo(spi);
@@ -1372,6 +1378,8 @@ static void stm32fx_spi_transfer_one_dma_start(struct stm32_spi *spi)
 		 */
 		stm32_spi_set_bits(spi, STM32FX_SPI_CR2, STM32FX_SPI_CR2_ERRIE);
 	}
+
+	stm32_spi_enable(spi);
 }
 
 /**
@@ -1405,6 +1413,8 @@ static void stm32h7_spi_transfer_one_dma_start(struct stm32_spi *spi)
 
 	stm32_spi_set_bits(spi, STM32H7_SPI_IER, ier);
 
+	stm32_spi_enable(spi);
+
 	if (STM32_SPI_HOST_MODE(spi))
 		stm32_spi_set_bits(spi, STM32H7_SPI_CR1, STM32H7_SPI_CR1_CSTART);
 }