spi: stm32h7: fix full duplex irq handler handling

In case of Full-Duplex mode, DXP flag is set when RXP and TXP flags are
set. But to avoid 2 different handlings, just add TXP and RXP flag in
the mask instead of DXP, and then keep the initial handling of TXP and
RXP events.
Also rephrase comment about EOTIE which is one of the interrupt enable
bits. It is not triggered by any event.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Reviewed-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/1625042723-661-3-git-send-email-alain.volmat@foss.st.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-stm32.c

@@ -884,15 +884,18 @@ static irqreturn_t stm32h7_spi_irq_thread(int irq, void *dev_id)
 	ier = readl_relaxed(spi->base + STM32H7_SPI_IER);
 
 	mask = ier;
-	/* EOTIE is triggered on EOT, SUSP and TXC events. */
+	/*
+	 * EOTIE enables irq from EOT, SUSP and TXC events. We need to set
+	 * SUSP to acknowledge it later. TXC is automatically cleared
+	 */
+
 	mask |= STM32H7_SPI_SR_SUSP;
 	/*
-	 * When TXTF is set, DXPIE and TXPIE are cleared. So in case of
-	 * Full-Duplex, need to poll RXP event to know if there are remaining
-	 * data, before disabling SPI.
+	 * DXPIE is set in Full-Duplex, one IT will be raised if TXP and RXP
+	 * are set. So in case of Full-Duplex, need to poll TXP and RXP event.
 	 */
-	if (spi->rx_buf && !spi->cur_usedma)
-		mask |= STM32H7_SPI_SR_RXP;
+	if ((spi->cur_comm == SPI_FULL_DUPLEX) && !spi->cur_usedma)
+		mask |= STM32H7_SPI_SR_TXP | STM32H7_SPI_SR_RXP;
 
 	if (!(sr & mask)) {
 		dev_warn(spi->dev, "spurious IT (sr=0x%08x, ier=0x%08x)\n",