From: Artur Jedrysek <jartur@cadence.com>
To: Marek Vasut <marek.vasut@gmail.com>,
        "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Cyrille Pitchen <cyrille.pitchen@atmel.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Boris Brezillon <boris.brezillon@free-electrons.com>,
        Richard Weinberger <richard@nod.at>
Subject: RE: [v2, 2/4] mtd: spi-nor: Add Octal SPI support to Cadence QSPI
 driver.
Thread-Topic: [v2, 2/4] mtd: spi-nor: Add Octal SPI support to Cadence QSPI
 driver.
Thread-Index: AQHSl+J0sYoB0K7MN0ue0U4PecUqKKGNb3QAgACJu8A=
Date: Fri, 10 Mar 2017 12:00:45 +0000
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References: <1488959932-6657-1-git-send-email-jartur@cadence.com>
 <1488960178-11079-1-git-send-email-jartur@cadence.com>
 <891f9177-e03c-85e0-ebab-2dc7df2ce9e0@gmail.com>
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From: Marek Vasut [mailto:marek.vasut@gmail.com]
Sent: 10 March 2017 04:37
> On 03/08/2017 09:02 AM, Artur Jedrysek wrote:
> > Recent versions of Cadence QSPI controller support Octal SPI transfers
> > as well. This patch updates existing driver to support such feature.
> >
> > It is not possible to determine whether or not octal mode is supported
> > just by looking at revision register alone. To solve that, an additional
> > compatible in Device Tree is added to indicate such capability.
> > Both (revision and compatible) are used to determine, which mode to
> > pass to spi_nor_scan() call.
> >
> > Signed-off-by: Artur Jedrysek <jartur@cadence.com>
> > ---
> > Changelog:
> > v2: Use new compatible in DT, instead of boolean property, to indicate
> > Octal SPI support.
> > Extracted Kconfig update to seperate patch.
> > ---
> >  drivers/mtd/spi-nor/cadence-quadspi.c | 69 +++++++++++++++++++++++++++++++----
> >  1 file changed, 61 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
> > index 9f8102d..a96471d 100644
> > --- a/drivers/mtd/spi-nor/cadence-quadspi.c
> > +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
> > @@ -76,6 +76,7 @@ struct cqspi_st {
> >  	u32			fifo_depth;
> >  	u32			fifo_width;
> >  	u32			trigger_address;
> > +	u32			max_mode;
> 
> I think it's time to introduce flags instead,
> ie. #define CQSPI_FLAG_SUPPORTS_OCTAL BIT(0)
> 
> >  	struct cqspi_flash_pdata f_pdata[CQSPI_MAX_CHIPSELECT];
> >  };
> >
> > @@ -87,6 +88,10 @@ struct cqspi_st {
> >  #define CQSPI_INST_TYPE_SINGLE			0
> >  #define CQSPI_INST_TYPE_DUAL			1
> >  #define CQSPI_INST_TYPE_QUAD			2
> > +#define CQSPI_INST_TYPE_OCTAL			3
> > +
> > +#define CQSPI_MAX_MODE_QUAD			0
> > +#define CQSPI_MAX_MODE_OCTAL			1
> >
> >  #define CQSPI_DUMMY_CLKS_PER_BYTE		8
> >  #define CQSPI_DUMMY_BYTES_MAX			4
> > @@ -204,6 +209,14 @@ struct cqspi_st {
> >  #define CQSPI_REG_CMDWRITEDATALOWER		0xA8
> >  #define CQSPI_REG_CMDWRITEDATAUPPER		0xAC
> >
> > +#define CQSPI_REG_MODULEID			0xFC
> > +#define CQSPI_REG_MODULEID_CONF_ID_MASK		0x3
> > +#define CQSPI_REG_MODULEID_CONF_ID_LSB		0
> > +#define CQSPI_REG_MODULEID_CONF_ID_OCTAL_PHY	0x0
> > +#define CQSPI_REG_MODULEID_CONF_ID_OCTAL	0x1
> > +#define CQSPI_REG_MODULEID_CONF_ID_QUAD_PHY	0x2
> > +#define CQSPI_REG_MODULEID_CONF_ID_QUAD		0x3
> > +
> >  /* Interrupt status bits */
> >  #define CQSPI_REG_IRQ_MODE_ERR			BIT(0)
> >  #define CQSPI_REG_IRQ_UNDERFLOW			BIT(1)
> > @@ -866,6 +879,9 @@ static int cqspi_set_protocol(struct spi_nor *nor, const int read)
> >  		case SPI_NOR_QUAD:
> >  			f_pdata->data_width = CQSPI_INST_TYPE_QUAD;
> >  			break;
> > +		case SPI_NOR_OCTAL:
> > +			f_pdata->data_width = CQSPI_INST_TYPE_OCTAL;
> > +			break;
> >  		default:
> >  			return -EINVAL;
> >  		}
> > @@ -977,6 +993,17 @@ static int cqspi_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
> >  	return ret;
> >  }
> >
> > +static const u32 cqspi_max_mode_quad = CQSPI_MAX_MODE_QUAD;
> > +static const u32 cqspi_max_mode_octal = CQSPI_MAX_MODE_OCTAL;
> > +
> > +static struct of_device_id const cqspi_dt_ids[] = {
> > +	{ .compatible = "cdns,qspi-nor", .data = &cqspi_max_mode_quad },
> > +	{ .compatible = "cdns,ospi-nor", .data = &cqspi_max_mode_octal },
> 
> .data = (void *)CQSPI_FLAG_SUPPORTS_OCTAL , then you don't need that
> static const stuff ...
> 

I had some doubts regarding that approach, as it may be dependent on the
CPU architecture (32-bit, 64-bit) and endianness. .data needs to be first
casted to unsigned long for reading, to ensure correct access and to 
allow bitwise operations on it. That solution works, and if such approach
is preferred, then it will be used in next version of the patch.

> > +	{ /* end of table */ }
> > +};
> > +
> > +MODULE_DEVICE_TABLE(of, cqspi_dt_ids);
> > +
> >  static int cqspi_of_get_flash_pdata(struct platform_device *pdev,
> >  				    struct cqspi_flash_pdata *f_pdata,
> >  				    struct device_node *np)
> > @@ -1018,6 +1045,13 @@ static int cqspi_of_get_pdata(struct platform_device *pdev)
> >  {
> >  	struct device_node *np = pdev->dev.of_node;
> >  	struct cqspi_st *cqspi = platform_get_drvdata(pdev);
> > +	const struct of_device_id *match;
> > +
> > +	cqspi->max_mode = CQSPI_MAX_MODE_QUAD;
> > +
> > +	match = of_match_node(cqspi_dt_ids, np);
> > +	if (match && match->data)
> > +		cqspi->max_mode = *((u32 *)match->data);
> 
> Use flags instead, see above.
> 
> >  	cqspi->is_decoded_cs = of_property_read_bool(np, "cdns,is-decoded-cs");
> >
> > @@ -1074,9 +1108,35 @@ static int cqspi_setup_flash(struct cqspi_st *cqspi, struct device_node *np)
> >  	struct cqspi_flash_pdata *f_pdata;
> >  	struct spi_nor *nor;
> >  	struct mtd_info *mtd;
> > +	enum read_mode mode;
> > +	enum read_mode dt_mode = SPI_NOR_QUAD;
> >  	unsigned int cs;
> > +	unsigned int rev_reg;
> >  	int i, ret;
> >
> > +	/* Determine, whether or not octal transfer MAY be supported */
> 
> But you already know that from DT, no ?
> 

Cadence Octal (formerly Quad) SPI Controller is sold as an IP, and is
configurable. This includes max SPI mode. It is possible to detect, that
Octal SPI controller is configured (during hardware compilation) to support
up to Quad mode, using revision register.

> > +	rev_reg = readl(cqspi->iobase + CQSPI_REG_MODULEID);
> > +	dev_info(dev, "CQSPI Module id %x\n", rev_reg);
> > +
> > +	switch (rev_reg & CQSPI_REG_MODULEID_CONF_ID_MASK) {
> > +	case CQSPI_REG_MODULEID_CONF_ID_OCTAL_PHY:
> > +	case CQSPI_REG_MODULEID_CONF_ID_OCTAL:
> > +		mode = SPI_NOR_OCTAL;
> > +		break;
> > +	case CQSPI_REG_MODULEID_CONF_ID_QUAD:
> > +	case CQSPI_REG_MODULEID_CONF_ID_QUAD_PHY:
> 
> Does this work on all revisions of CQSPI ?
> 

After having a more thorough look at specification of older IP version
(quad only) it seems, that revision register format has indeed changed.
This will be fixed in the next version of the patch.

> > +		mode = SPI_NOR_QUAD;
> > +		break;
> > +	}
> > +
> > +	if (cqspi->max_mode == CQSPI_MAX_MODE_OCTAL)
> > +		dt_mode = SPI_NOR_OCTAL;
> > +
> > +	if (mode == SPI_NOR_QUAD && dt_mode == SPI_NOR_OCTAL)
> > +		dev_warn(dev, "Requested octal mode is not supported by the device.");
> > +	else if (mode == SPI_NOR_OCTAL && dt_mode == SPI_NOR_QUAD)
> > +		mode = SPI_NOR_QUAD;
> > +
> >  	/* Get flash device data */
> >  	for_each_available_child_of_node(dev->of_node, np) {
> >  		ret = of_property_read_u32(np, "reg", &cs);
> > @@ -1123,7 +1183,7 @@ static int cqspi_setup_flash(struct cqspi_st *cqspi, struct device_node *np)
> >  			goto err;
> >  		}
> >
> > -		ret = spi_nor_scan(nor, NULL, SPI_NOR_QUAD);
> > +		ret = spi_nor_scan(nor, NULL, mode);
> >  		if (ret)
> >  			goto err;
> >
> > @@ -1277,13 +1337,6 @@ static const struct dev_pm_ops cqspi__dev_pm_ops = {
> >  #define CQSPI_DEV_PM_OPS	NULL
> >  #endif
> >
> > -static struct of_device_id const cqspi_dt_ids[] = {
> > -	{.compatible = "cdns,qspi-nor",},
> > -	{ /* end of table */ }
> > -};
> > -
> > -MODULE_DEVICE_TABLE(of, cqspi_dt_ids);
> > -
> >  static struct platform_driver cqspi_platform_driver = {
> >  	.probe = cqspi_probe,
> >  	.remove = cqspi_remove,
> >
> 
> 
> --
> Best regards,
> Marek Vasut