[PATCH v4 1/6] spi: cadence-qspi: allow FIFO depth detection

[Théo Lebrun <theo.lebrun@xxxxxxxxxxx>]

If FIFO depth DT property is provided, check it matches what hardware
reports and warn otherwise. Else, use hardware provided value.

Hardware exposes FIFO depth indirectly because
CQSPI_REG_SRAMPARTITION is partially read-only.

Move probe cqspi->ddata assignment prior to cqspi_of_get_pdata() call.

Signed-off-by: Théo Lebrun <theo.lebrun@xxxxxxxxxxx>
---
 drivers/spi/spi-cadence-quadspi.c | 37 ++++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index 9896e9fe7ffb..5a83940220a9 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -1510,8 +1510,8 @@ static int cqspi_of_get_pdata(struct cqspi_st *cqspi)
 	cqspi->is_decoded_cs = of_property_read_bool(np, "cdns,is-decoded-cs");
 
 	if (of_property_read_u32(np, "cdns,fifo-depth", &cqspi->fifo_depth)) {
-		dev_err(dev, "couldn't determine fifo-depth\n");
-		return -ENXIO;
+		/* Zero signals FIFO depth should be runtime detected. */
+		cqspi->fifo_depth = 0;
 	}
 
 	if (of_property_read_u32(np, "cdns,fifo-width", &cqspi->fifo_width)) {
@@ -1541,8 +1541,6 @@ static void cqspi_controller_init(struct cqspi_st *cqspi)
 {
 	u32 reg;
 
-	cqspi_controller_enable(cqspi, 0);
-
 	/* Configure the remap address register, no remap */
 	writel(0, cqspi->iobase + CQSPI_REG_REMAP);
 
@@ -1576,8 +1574,29 @@ static void cqspi_controller_init(struct cqspi_st *cqspi)
 		reg |= CQSPI_REG_CONFIG_DMA_MASK;
 		writel(reg, cqspi->iobase + CQSPI_REG_CONFIG);
 	}
+}
 
-	cqspi_controller_enable(cqspi, 1);
+static void cqspi_controller_detect_fifo_depth(struct cqspi_st *cqspi)
+{
+	struct device *dev = &cqspi->pdev->dev;
+	u32 reg, fifo_depth;
+
+	/*
+	 * Bits N-1:0 are writable while bits 31:N are read as zero, with 2^N
+	 * the FIFO depth.
+	 */
+	writel(U32_MAX, cqspi->iobase + CQSPI_REG_SRAMPARTITION);
+	reg = readl(cqspi->iobase + CQSPI_REG_SRAMPARTITION);
+	fifo_depth = reg + 1;
+
+	/* FIFO depth of zero means no value from devicetree was provided. */
+	if (cqspi->fifo_depth == 0) {
+		cqspi->fifo_depth = fifo_depth;
+		dev_dbg(dev, "using FIFO depth of %u\n", fifo_depth);
+	} else if (fifo_depth != cqspi->fifo_depth) {
+		dev_warn(dev, "detected FIFO depth (%u) different from config (%u)\n",
+			 fifo_depth, cqspi->fifo_depth);
+	}
 }
 
 static int cqspi_request_mmap_dma(struct cqspi_st *cqspi)
@@ -1730,6 +1749,7 @@ static int cqspi_probe(struct platform_device *pdev)
 	cqspi->pdev = pdev;
 	cqspi->host = host;
 	cqspi->is_jh7110 = false;
+	cqspi->ddata = ddata = of_device_get_match_data(dev);
 	platform_set_drvdata(pdev, cqspi);
 
 	/* Obtain configuration from OF. */
@@ -1821,8 +1841,6 @@ static int cqspi_probe(struct platform_device *pdev)
 	/* write completion is supported by default */
 	cqspi->wr_completion = true;
 
-	ddata = of_device_get_match_data(dev);
-	cqspi->ddata = ddata;
 	if (ddata) {
 		if (ddata->quirks & CQSPI_NEEDS_WR_DELAY)
 			cqspi->wr_delay = 50 * DIV_ROUND_UP(NSEC_PER_SEC,
@@ -1864,7 +1882,10 @@ static int cqspi_probe(struct platform_device *pdev)
 	}
 
 	cqspi_wait_idle(cqspi);
+	cqspi_controller_enable(cqspi, 0);
+	cqspi_controller_detect_fifo_depth(cqspi);
 	cqspi_controller_init(cqspi);
+	cqspi_controller_enable(cqspi, 1);
 	cqspi->current_cs = -1;
 	cqspi->sclk = 0;
 
@@ -1947,7 +1968,9 @@ static int cqspi_runtime_resume(struct device *dev)
 
 	clk_prepare_enable(cqspi->clk);
 	cqspi_wait_idle(cqspi);
+	cqspi_controller_enable(cqspi, 0);
 	cqspi_controller_init(cqspi);
+	cqspi_controller_enable(cqspi, 1);
 
 	cqspi->current_cs = -1;
 	cqspi->sclk = 0;

-- 
2.44.0