spi: spi-rockchip: add support for spi slave mode

Add support for spi slave mode in spi-rockchip. The register map has an entry
for it. If spi-slave is set in dts, set this corresponding bit and add to
mode_bits the SPI_NO_CS, allow slave mode without explicit CS use.
Slave abort function had been added.
Signed-off-by: Chris Ruehl <chris.ruehl@gtsys.com.hk>
Link: https://lore.kernel.org/r/20200511083022.23678-3-chris.ruehl@gtsys.com.hkSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rockchip.c

@@ -183,6 +183,8 @@ struct rockchip_spi {
 	u8 rsd;
 
 	bool cs_asserted[ROCKCHIP_SPI_MAX_CS_NUM];
+
+	bool slave_abort;
 };
 
 static inline void spi_enable_chip(struct rockchip_spi *rs, bool enable)
@@ -359,7 +361,7 @@ static void rockchip_spi_dma_rxcb(void *data)
 	struct rockchip_spi *rs = spi_controller_get_devdata(ctlr);
 	int state = atomic_fetch_andnot(RXDMA, &rs->state);
 
-	if (state & TXDMA)
+	if (state & TXDMA && !rs->slave_abort)
 		return;
 
 	spi_enable_chip(rs, false);
@@ -372,7 +374,7 @@ static void rockchip_spi_dma_txcb(void *data)
 	struct rockchip_spi *rs = spi_controller_get_devdata(ctlr);
 	int state = atomic_fetch_andnot(TXDMA, &rs->state);
 
-	if (state & RXDMA)
+	if (state & RXDMA && !rs->slave_abort)
 		return;
 
 	/* Wait until the FIFO data completely. */
@@ -457,7 +459,7 @@ static int rockchip_spi_prepare_dma(struct rockchip_spi *rs,
 
 static void rockchip_spi_config(struct rockchip_spi *rs,
 		struct spi_device *spi, struct spi_transfer *xfer,
-		bool use_dma)
+		bool use_dma, bool slave_mode)
 {
 	u32 cr0 = CR0_FRF_SPI  << CR0_FRF_OFFSET
 	        | CR0_BHT_8BIT << CR0_BHT_OFFSET
@@ -466,6 +468,10 @@ static void rockchip_spi_config(struct rockchip_spi *rs,
 	u32 cr1;
 	u32 dmacr = 0;
 
+	if (slave_mode)
+		cr0 |= CR0_OPM_SLAVE << CR0_OPM_OFFSET;
+	rs->slave_abort = false;
+
 	cr0 |= rs->rsd << CR0_RSD_OFFSET;
 	cr0 |= (spi->mode & 0x3U) << CR0_SCPH_OFFSET;
 	if (spi->mode & SPI_LSB_FIRST)
@@ -535,6 +541,16 @@ static size_t rockchip_spi_max_transfer_size(struct spi_device *spi)
 	return ROCKCHIP_SPI_MAX_TRANLEN;
 }
 
+static int rockchip_spi_slave_abort(struct spi_controller *ctlr)
+{
+	struct rockchip_spi *rs = spi_controller_get_devdata(ctlr);
+
+	rs->slave_abort = true;
+	complete(&ctlr->xfer_completion);
+
+	return 0;
+}
+
 static int rockchip_spi_transfer_one(
 		struct spi_controller *ctlr,
 		struct spi_device *spi,
@@ -560,7 +576,7 @@ static int rockchip_spi_transfer_one(
 
 	use_dma = ctlr->can_dma ? ctlr->can_dma(ctlr, spi, xfer) : false;
 
-	rockchip_spi_config(rs, spi, xfer, use_dma);
+	rockchip_spi_config(rs, spi, xfer, use_dma, ctlr->slave);
 
 	if (use_dma)
 		return rockchip_spi_prepare_dma(rs, ctlr, xfer);
@@ -588,15 +604,26 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 	struct rockchip_spi *rs;
 	struct spi_controller *ctlr;
 	struct resource *mem;
+	struct device_node *np = pdev->dev.of_node;
 	u32 rsd_nsecs;
+	bool slave_mode;
+
+	slave_mode = of_property_read_bool(np, "spi-slave");
+
+	if (slave_mode)
+		ctlr = spi_alloc_slave(&pdev->dev,
+				sizeof(struct rockchip_spi));
+	else
+		ctlr = spi_alloc_master(&pdev->dev,
+				sizeof(struct rockchip_spi));
 
-	ctlr = spi_alloc_master(&pdev->dev, sizeof(struct rockchip_spi));
 	if (!ctlr)
 		return -ENOMEM;
 
 	platform_set_drvdata(pdev, ctlr);
 
 	rs = spi_controller_get_devdata(ctlr);
+	ctlr->slave = slave_mode;
 
 	/* Get basic io resource and map it */
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -676,6 +703,12 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 	ctlr->auto_runtime_pm = true;
 	ctlr->bus_num = pdev->id;
 	ctlr->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP | SPI_LSB_FIRST;
+	if (slave_mode) {
+		ctlr->mode_bits |= SPI_NO_CS;
+		ctlr->slave_abort = rockchip_spi_slave_abort;
+	} else {
+		ctlr->flags = SPI_MASTER_GPIO_SS;
+	}
 	ctlr->num_chipselect = ROCKCHIP_SPI_MAX_CS_NUM;
 	ctlr->dev.of_node = pdev->dev.of_node;
 	ctlr->bits_per_word_mask = SPI_BPW_MASK(16) | SPI_BPW_MASK(8) | SPI_BPW_MASK(4);
@@ -686,7 +719,6 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 	ctlr->transfer_one = rockchip_spi_transfer_one;
 	ctlr->max_transfer_size = rockchip_spi_max_transfer_size;
 	ctlr->handle_err = rockchip_spi_handle_err;
-	ctlr->flags = SPI_MASTER_GPIO_SS;
 
 	ctlr->dma_tx = dma_request_chan(rs->dev, "tx");
 	if (IS_ERR(ctlr->dma_tx)) {