[PATCH v2 1/2] mtd: fsl-quadspi: Update slave device hwcap based on mode provided in dtsi file

Hi Cyrille,

-----Original Message-----
From: Cyrille Pitchen [mailto:cyrille.pitchen at wedev4u.fr]
Sent: Tuesday, February 06, 2018 2:19 AM
To: Yogesh Narayan Gaur <redacted>; linux-
mtd at lists.infradead.org; devicetree at vger.kernel.org; robh at kernel.org;
mark.rutland at arm.com; shawnguo at kernel.org
Cc: linux-arm-kernel at lists.infradead.org; boris.brezillon at free-electrons.com;
computersforpeace at gmail.com; Han Xu [off-list ref];
festevam at gmail.com; Prabhakar Kushwaha [off-list ref];
Suresh Gupta [off-list ref]
Subject: Re: [PATCH v2 1/2] mtd: fsl-quadspi: Update slave device hwcap based
on mode provided in dtsi file

Hi Yogesh,

Le 02/02/2018 ? 06:31, Yogesh Gaur a ?crit?:

quoted

FSL QuadSPI controller supports Single, dual, quad modes of operation.
Mode information is available via "spi-tx-bus-width" and
"spi-rx-bus-width" nodes of device tree for the connected slave device.

Update read and write hwcap capability for slave device by reading
"spi-rx-bus-width" and "spi-tx-bus-width" respectively.
Assign hwcaps mask to minimal caps for the slave node i.e.
	SNOR_HWCAPS_READ | SNOR_HWCAPS_PP

If value not provided in device tree file, then fallback to default
mode i.e. SNOR_HWCAPS_READ_1_1_4 and SNOR_HWCAPS_PP.

Signed-off-by: Prabhakar Kushwaha <redacted>
Signed-off-by: Yogesh Gaur <redacted>
---
Changes for v2:
- None

 drivers/mtd/spi-nor/fsl-quadspi.c | 56
+++++++++++++++++++++++++++++++++++----
 1 file changed, 51 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c

b/drivers/mtd/spi-nor/fsl-quadspi.c
index b9c5918..1503e0c 100644

--- a/drivers/mtd/spi-nor/fsl-quadspi.c
+++ b/drivers/mtd/spi-nor/fsl-quadspi.c

@@ -994,17 +994,14 @@ static void fsl_qspi_unprep(struct spi_nor *nor,

enum spi_nor_ops ops)

 static int fsl_qspi_probe(struct platform_device *pdev)  {
-	const struct spi_nor_hwcaps hwcaps = {
-		.mask = SNOR_HWCAPS_READ_1_1_4 |
-			SNOR_HWCAPS_PP,
-	};
+	struct spi_nor_hwcaps hwcaps;
 	struct device_node *np = pdev->dev.of_node;
 	struct device *dev = &pdev->dev;
 	struct fsl_qspi *q;
 	struct resource *res;
 	struct spi_nor *nor;
 	struct mtd_info *mtd;
-	int ret, i = 0;
+	int ret, i = 0, value;

 	q = devm_kzalloc(dev, sizeof(*q), GFP_KERNEL);
 	if (!q)

@@ -1077,6 +1074,10 @@ static int fsl_qspi_probe(struct

platform_device *pdev)

 	/* iterate the subnodes. */
 	for_each_available_child_of_node(dev->of_node, np) {
+		/* Reset hwcaps mask to minimal caps for the slave node. */
+		hwcaps.mask = SNOR_HWCAPS_READ | SNOR_HWCAPS_PP;
+		value = 0;
+
 		/* skip the holes */
 		if (!q->has_second_chip)
 			i *= 2;

@@ -1106,6 +1107,51 @@ static int fsl_qspi_probe(struct platform_device

*pdev)

quoted

 		/* set the chip address for READID */
 		fsl_qspi_set_base_addr(q, nor);

+		/*
+		 * If spi-rx-bus-width and spi-tx-bus-width not defined assign
+		 * default hardware capabilities SNOR_HWCAPS_READ_1_1_4

and

quoted

+		 * SNOR_HWCAPS_PP supported by the Quad-SPI controller.
+		 */
+		if (!of_property_read_u32(np, "spi-rx-bus-width", &value)) {
+			switch (value) {
+			case 1:
+				hwcaps.mask |= SNOR_HWCAPS_READ |
+					       SNOR_HWCAPS_READ_FAST;
+				break;
+			case 2:
+				hwcaps.mask |= SNOR_HWCAPS_READ_1_1_2

|

quoted

+					       SNOR_HWCAPS_READ_1_2_2;

I guess there is a misunderstanding in the meaning of spi-rx-bus-width and spi-
tx-bus_width.

spi-rx-bus-width = <N>, resp. spi-tx-bus-width = <N>, means the SPI controller
can receive, resp. send, data on N I/O Lines.

Then let's take the example of some Fast Read X-Y-Z command:

the op code is *sent* on X I/O lines: you need to check spi-tx-bus-width the
address/mode/dummy bits are *sent* on Y I/O lines: check spi-tx-bus-width too
the data bits are *received* on Z I/O lines: check spi-rx-bus_width.

quoted

+				break;
+			case 4:
+				hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4

|

quoted

+					       SNOR_HWCAPS_READ_1_4_4;

The same here: to allow SPI 1-4-4, you have to check that spi-tx-bus-width == 4.

So your usage of spi-{tx|rx}-bus-width is not consistent with the usage done in
the SPI subsystem. Please have a look at drivers/mtd/devices/m25p80.c,
especially how the SPI_RX_QUAD and SPI_TX_QUAD flags are used in the
m25p_probe() function to have a better idea of how it should work.

Also have a look at of_spi_parse_dt() in drivers/spi/spi.c, to figure out how the
SPI_{TX|RX}_{DUAL|QUAD} flags are set according to the spi-{tx|rx}-bus-width
DT properties.

Thanks for review, would incorporate your review comments and would have usage of spi-{rx/tx}-bus-width as being done in SPI subsystem.

quoted

+				break;
+			default:
+				dev_err(dev,
+					"spi-rx-bus-width %d not supported\n",
+					value);
+				break;
+			}
+		} else
+			hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4;

Not sure whether it passes checkpatch, you may have to add { } for the else
statement even if there is a single line as the if statement use { }.

I have run ' ./scripts/checkpatch.pl' present in linux-mtd code base and it hasn't reported any warning or error messages.
Meanwhile, would add {} braces for this else statement also.

--
Regards
Yogesh Gaur.

Personally I don't mind that much. Please just check that your patch passes
checkpatch verification and it will be okay for me :)

Best regards,

Cyrille

quoted

+
+		if (!of_property_read_u32(np, "spi-tx-bus-width", &value)) {
+			switch (value) {
+			case 1:
+				hwcaps.mask |= SNOR_HWCAPS_PP;
+				break;
+			case 4:
+				hwcaps.mask |= SNOR_HWCAPS_PP_1_1_4 |
+					       SNOR_HWCAPS_PP_1_4_4;
+				break;
+			default:
+				dev_err(dev,
+					"spi-tx-bus-width %d not supported\n",
+					value);
+				break;
+			}
+		}
+
 		ret = spi_nor_scan(nor, NULL, &hwcaps);
 		if (ret)
 			goto mutex_failed;