spi: microchip-core-qspi: Add regular transfers

The driver for CoreQSPI only supports memory operations at present, so
add support for regular transfers so that the SD card slot and ADC on
the BeagleV Fire can be used.

Signed-off-by: Cyril Jean <cyril.jean@microchip.com>
Co-developed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20250620-splice-shelter-310771564886@spud
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Cyril-Jean

drivers/spi/spi-microchip-core-qspi.c

@@ -222,6 +222,87 @@ static inline void mchp_coreqspi_write_op(struct mchp_coreqspi *qspi)
 	}
 }
 
+static inline void mchp_coreqspi_write_read_op(struct mchp_coreqspi *qspi)
+{
+	u32 control, data;
+
+	qspi->rx_len = qspi->tx_len;
+
+	control = readl_relaxed(qspi->regs + REG_CONTROL);
+	control |= CONTROL_FLAGSX4;
+	writel_relaxed(control, qspi->regs + REG_CONTROL);
+
+	while (qspi->tx_len >= 4) {
+		while (readl_relaxed(qspi->regs + REG_STATUS) & STATUS_TXFIFOFULL)
+			;
+
+		data = qspi->txbuf ? *((u32 *)qspi->txbuf) : 0xaa;
+		if (qspi->txbuf)
+			qspi->txbuf += 4;
+		qspi->tx_len -= 4;
+		writel_relaxed(data, qspi->regs + REG_X4_TX_DATA);
+
+		/*
+		 * The rx FIFO is twice the size of the tx FIFO, so there is
+		 * no requirement to block transmission if receive data is not
+		 * ready, and it is fine to let the tx FIFO completely fill
+		 * without reading anything from the rx FIFO. Once the tx FIFO
+		 * has been filled and becomes non-full due to a transmission
+		 * occurring there will always be something to receive.
+		 * IOW, this is safe as TX_FIFO_SIZE + 4 < 2 * TX_FIFO_SIZE
+		 */
+		if (qspi->rx_len >= 4) {
+			if (readl_relaxed(qspi->regs + REG_STATUS) & STATUS_RXAVAILABLE) {
+				data = readl_relaxed(qspi->regs + REG_X4_RX_DATA);
+				*(u32 *)qspi->rxbuf = data;
+				qspi->rxbuf += 4;
+				qspi->rx_len -= 4;
+			}
+		}
+	}
+
+	/*
+	 * Since transmission is not being blocked by clearing the rx FIFO,
+	 * loop here until all received data "leaked" by the loop above has
+	 * been dealt with.
+	 */
+	while (qspi->rx_len >= 4) {
+		while (readl_relaxed(qspi->regs + REG_STATUS) & STATUS_RXFIFOEMPTY)
+			;
+		data = readl_relaxed(qspi->regs + REG_X4_RX_DATA);
+		*(u32 *)qspi->rxbuf = data;
+		qspi->rxbuf += 4;
+		qspi->rx_len -= 4;
+	}
+
+	/*
+	 * Since rx_len and tx_len must be < 4 bytes at this point, there's no
+	 * concern about overflowing the rx or tx FIFOs any longer. It's
+	 * therefore safe to loop over the remainder of the transmit data before
+	 * handling the remaining receive data.
+	 */
+	if (!qspi->tx_len)
+		return;
+
+	control &= ~CONTROL_FLAGSX4;
+	writel_relaxed(control, qspi->regs + REG_CONTROL);
+
+	while (qspi->tx_len--) {
+		while (readl_relaxed(qspi->regs + REG_STATUS) & STATUS_TXFIFOFULL)
+			;
+		data = qspi->txbuf ? *qspi->txbuf : 0xaa;
+		qspi->txbuf++;
+		writel_relaxed(data, qspi->regs + REG_TX_DATA);
+	}
+
+	while (qspi->rx_len--) {
+		while (readl_relaxed(qspi->regs + REG_STATUS) & STATUS_RXFIFOEMPTY)
+			;
+		data = readl_relaxed(qspi->regs + REG_RX_DATA);
+		*qspi->rxbuf++ = (data & 0xFF);
+	}
+}
+
 static void mchp_coreqspi_enable_ints(struct mchp_coreqspi *qspi)
 {
 	u32 mask = IEN_TXDONE |
@@ -266,7 +347,7 @@ static irqreturn_t mchp_coreqspi_isr(int irq, void *dev_id)
 }
 
 static int mchp_coreqspi_setup_clock(struct mchp_coreqspi *qspi, struct spi_device *spi,
-				     const struct spi_mem_op *op)
+				     u32 max_freq)
 {
 	unsigned long clk_hz;
 	u32 control, baud_rate_val = 0;
@@ -275,11 +356,11 @@ static int mchp_coreqspi_setup_clock(struct mchp_coreqspi *qspi, struct spi_devi
 	if (!clk_hz)
 		return -EINVAL;
 
-	baud_rate_val = DIV_ROUND_UP(clk_hz, 2 * op->max_freq);
+	baud_rate_val = DIV_ROUND_UP(clk_hz, 2 * max_freq);
 	if (baud_rate_val > MAX_DIVIDER || baud_rate_val < MIN_DIVIDER) {
 		dev_err(&spi->dev,
 			"could not configure the clock for spi clock %d Hz & system clock %ld Hz\n",
-			op->max_freq, clk_hz);
+			max_freq, clk_hz);
 		return -EINVAL;
 	}
 
@@ -367,23 +448,13 @@ static inline void mchp_coreqspi_config_op(struct mchp_coreqspi *qspi, const str
 	writel_relaxed(frames, qspi->regs + REG_FRAMES);
 }
 
-static int mchp_qspi_wait_for_ready(struct spi_mem *mem)
+static int mchp_coreqspi_wait_for_ready(struct mchp_coreqspi *qspi)
 {
-	struct mchp_coreqspi *qspi = spi_controller_get_devdata
-				    (mem->spi->controller);
 	u32 status;
-	int ret;
 
-	ret = readl_poll_timeout(qspi->regs + REG_STATUS, status,
+	return readl_poll_timeout(qspi->regs + REG_STATUS, status,
 				 (status & STATUS_READY), 0,
 				 TIMEOUT_MS);
-	if (ret) {
-		dev_err(&mem->spi->dev,
-			"Timeout waiting on QSPI ready.\n");
-		return -ETIMEDOUT;
-	}
-
-	return ret;
 }
 
 static int mchp_coreqspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
@@ -396,11 +467,13 @@ static int mchp_coreqspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *o
 	int err, i;
 
 	mutex_lock(&qspi->op_lock);
-	err = mchp_qspi_wait_for_ready(mem);
-	if (err)
+	err = mchp_coreqspi_wait_for_ready(qspi);
+	if (err) {
+		dev_err(&mem->spi->dev, "Timeout waiting on QSPI ready.\n");
 		goto error;
+	}
 
-	err = mchp_coreqspi_setup_clock(qspi, mem->spi, op);
+	err = mchp_coreqspi_setup_clock(qspi, mem->spi, op->max_freq);
 	if (err)
 		goto error;
 
@@ -515,6 +588,109 @@ static const struct spi_controller_mem_caps mchp_coreqspi_mem_caps = {
 	.per_op_freq = true,
 };
 
+static int mchp_coreqspi_unprepare_message(struct spi_controller *ctlr, struct spi_message *m)
+{
+	struct mchp_coreqspi *qspi = spi_controller_get_devdata(ctlr);
+
+	/*
+	 * This delay is required for the driver to function correctly,
+	 * but no explanation has been determined for why it is required.
+	 */
+	udelay(750);
+
+	mutex_unlock(&qspi->op_lock);
+
+	return 0;
+}
+
+static int mchp_coreqspi_prepare_message(struct spi_controller *ctlr, struct spi_message *m)
+{
+	struct mchp_coreqspi *qspi = spi_controller_get_devdata(ctlr);
+	struct spi_transfer *t = NULL;
+	u32 control, frames;
+	u32 total_bytes = 0, cmd_bytes = 0, idle_cycles = 0;
+	int ret;
+	bool quad = false, dual = false;
+
+	mutex_lock(&qspi->op_lock);
+	ret = mchp_coreqspi_wait_for_ready(qspi);
+	if (ret) {
+		mutex_unlock(&qspi->op_lock);
+		dev_err(&ctlr->dev, "Timeout waiting on QSPI ready.\n");
+		return ret;
+	}
+
+	ret = mchp_coreqspi_setup_clock(qspi, m->spi, m->spi->max_speed_hz);
+	if (ret) {
+		mutex_unlock(&qspi->op_lock);
+		return ret;
+	}
+
+	control = readl_relaxed(qspi->regs + REG_CONTROL);
+	control &= ~(CONTROL_MODE12_MASK | CONTROL_MODE0);
+	writel_relaxed(control, qspi->regs + REG_CONTROL);
+
+	reinit_completion(&qspi->data_completion);
+
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		total_bytes += t->len;
+		if (!cmd_bytes && !(t->tx_buf && t->rx_buf))
+			cmd_bytes = t->len;
+		if (!t->rx_buf)
+			cmd_bytes = total_bytes;
+		if (t->tx_nbits == SPI_NBITS_QUAD || t->rx_nbits == SPI_NBITS_QUAD)
+			quad = true;
+		else if (t->tx_nbits == SPI_NBITS_DUAL || t->rx_nbits == SPI_NBITS_DUAL)
+			dual = true;
+	}
+
+	control = readl_relaxed(qspi->regs + REG_CONTROL);
+	if (quad) {
+		control |= (CONTROL_MODE0 | CONTROL_MODE12_EX_RW);
+	} else if (dual) {
+		control &= ~CONTROL_MODE0;
+		control |= CONTROL_MODE12_FULL;
+	} else {
+		control &= ~(CONTROL_MODE12_MASK | CONTROL_MODE0);
+	}
+	writel_relaxed(control, qspi->regs + REG_CONTROL);
+
+	frames = total_bytes & BYTESUPPER_MASK;
+	writel_relaxed(frames, qspi->regs + REG_FRAMESUP);
+	frames = total_bytes & BYTESLOWER_MASK;
+	frames |= cmd_bytes << FRAMES_CMDBYTES_SHIFT;
+	frames |= idle_cycles << FRAMES_IDLE_SHIFT;
+	control = readl_relaxed(qspi->regs + REG_CONTROL);
+	if (control & CONTROL_MODE12_MASK)
+		frames |= (1 << FRAMES_SHIFT);
+
+	frames |= FRAMES_FLAGWORD;
+	writel_relaxed(frames, qspi->regs + REG_FRAMES);
+
+	return 0;
+};
+
+static int mchp_coreqspi_transfer_one(struct spi_controller *ctlr, struct spi_device *spi,
+				      struct spi_transfer *t)
+{
+	struct mchp_coreqspi *qspi = spi_controller_get_devdata(ctlr);
+
+	qspi->tx_len = t->len;
+
+	if (t->tx_buf)
+		qspi->txbuf = (u8 *)t->tx_buf;
+
+	if (!t->rx_buf) {
+		mchp_coreqspi_write_op(qspi);
+	} else {
+		qspi->rxbuf = (u8 *)t->rx_buf;
+		qspi->rx_len = t->len;
+		mchp_coreqspi_write_read_op(qspi);
+	}
+
+	return 0;
+}
+
 static int mchp_coreqspi_probe(struct platform_device *pdev)
 {
 	struct spi_controller *ctlr;
@@ -563,6 +739,11 @@ static int mchp_coreqspi_probe(struct platform_device *pdev)
 			  SPI_TX_DUAL | SPI_TX_QUAD;
 	ctlr->dev.of_node = np;
 	ctlr->min_speed_hz = clk_get_rate(qspi->clk) / 30;
+	ctlr->prepare_message = mchp_coreqspi_prepare_message;
+	ctlr->unprepare_message = mchp_coreqspi_unprepare_message;
+	ctlr->transfer_one = mchp_coreqspi_transfer_one;
+	ctlr->num_chipselect = 2;
+	ctlr->use_gpio_descriptors = true;
 
 	ret = devm_spi_register_controller(&pdev->dev, ctlr);
 	if (ret)