Re: [PATCH v2 2/2] mtd: spi-nor: add driver for STM32 quad spi flash controller

[Ludovic BARRE <ludovic.barre@st.com>]

On 04/07/2017 01:55 AM, Marek Vasut wrote:
> On 03/31/2017 07:02 PM, Ludovic Barre wrote:
>> From: Ludovic Barre <ludovic.barre@st.com>
>>
>> The quadspi is a specialized communication interface targeting single,
>> dual or quad SPI Flash memories.
>>
>> It can operate in any of the following modes:
>> -indirect mode: all the operations are performed using the quadspi
>>   registers
>> -read memory-mapped mode: the external Flash memory is mapped to the
>>   microcontroller address space and is seen by the system as if it was
>>   an internal memory
>>
>> Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
>> ---
>>   drivers/mtd/spi-nor/Kconfig         |   7 +
>>   drivers/mtd/spi-nor/Makefile        |   1 +
>>   drivers/mtd/spi-nor/stm32-quadspi.c | 690 ++++++++++++++++++++++++++++++++++++
>>   3 files changed, 698 insertions(+)
>>   create mode 100644 drivers/mtd/spi-nor/stm32-quadspi.c
>>
> [...]
>
>> +struct stm32_qspi_flash {
>> +	struct spi_nor nor;
>> +	u32 cs;
>> +	u32 fsize;
>> +	u32 presc;
>> +	struct stm32_qspi *qspi;
>> +};
> [...]
>
>> +struct stm32_qspi_cmd {
>> +	struct {
>> +		u8 addr_width;
>> +		u8 dummy;
>> +		u8 data;
>> +	} conf;
> Is there any benefit in having this structure here or could you just
> make the struct stm32_qspi_cmd flat ?
no benefit, it was just to regroup,  so I can do a flat structure
>
>> +	u8 opcode;
>> +	u32 framemode;
>> +	u32 qspimode;
>> +	u32 addr;
>> +	size_t len;
>> +	void *buf;
>> +};
> [...]
>
>> +static ssize_t stm32_qspi_read(struct spi_nor *nor, loff_t from, size_t len,
>> +			       u_char *buf)
>> +{
>> +	struct stm32_qspi_flash *flash = nor->priv;
>> +	struct stm32_qspi *qspi = flash->qspi;
>> +	struct stm32_qspi_cmd cmd;
>> +	int err;
>> +
>> +	dev_dbg(qspi->dev, "read(%#.2x): buf:%p from:%#.8x len:%#x\n",
>> +		nor->read_opcode, buf, (u32)from, len);
>> +
>> +	memset(&cmd, 0, sizeof(cmd));
>> +	cmd.opcode = nor->read_opcode;
>> +	cmd.conf.addr_width = nor->addr_width;
>> +	cmd.addr = (u32)from;
> loff_t (from) can be 64bit ... how do we handle this ?
I'm surprise by the question,
the SPI NOR device uses 3 Bytes or 4 bytes address mode.
So, the stm32 qspi controller has a 32 bit register for NOR address.
On the other hand the framework and other drivers used this variable 
(from) like
a 32 bits.
>
>> +	cmd.conf.data = 1;
>> +	cmd.conf.dummy = nor->read_dummy;
>> +	cmd.len = len;
>> +	cmd.buf = buf;
>> +	cmd.qspimode = qspi->read_mode;
>> +
>> +	stm32_qspi_set_framemode(nor, &cmd, true);
>> +	err = stm32_qspi_send(flash, &cmd);
>> +
>> +	return err ? err : len;
>> +}
> [...]
>
>> +static irqreturn_t stm32_qspi_irq(int irq, void *dev_id)
>> +{
>> +	struct stm32_qspi *qspi = (struct stm32_qspi *)dev_id;
>> +	u32 cr, sr, fcr = 0;
>> +
>> +	cr = readl_relaxed(qspi->io_base + QUADSPI_CR);
>> +	sr = readl_relaxed(qspi->io_base + QUADSPI_SR);
>> +
>> +	if ((cr & CR_TCIE) && (sr & SR_TCF)) {
>> +		/* tx complete */
>> +		fcr |= FCR_CTCF;
>> +		complete(&qspi->cmd_completion);
>> +	} else {
>> +		dev_info(qspi->dev, "spurious interrupt\n");
> You probably want to ratelimit this one ...
yes it's better if there is an issue.
>
>> +	}
>> +
>> +	writel_relaxed(fcr, qspi->io_base + QUADSPI_FCR);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static int stm32_qspi_prep(struct spi_nor *nor, enum spi_nor_ops ops)
>> +{
>> +	struct stm32_qspi_flash *flash = nor->priv;
>> +	struct stm32_qspi *qspi = flash->qspi;
>> +
>> +	mutex_lock(&qspi->lock);
>> +	return 0;
>> +}
>> +
>> +static void stm32_qspi_unprep(struct spi_nor *nor, enum spi_nor_ops ops)
>> +{
>> +	struct stm32_qspi_flash *flash = nor->priv;
>> +	struct stm32_qspi *qspi = flash->qspi;
>> +
>> +	mutex_unlock(&qspi->lock);
>> +}
>> +
>> +static int stm32_qspi_flash_setup(struct stm32_qspi *qspi,
>> +				  struct device_node *np)
>> +{
>> +	u32 width, flash_read, presc, cs_num, max_rate = 0;
>> +	struct stm32_qspi_flash *flash;
>> +	struct mtd_info *mtd;
>> +	int ret;
>> +
>> +	of_property_read_u32(np, "reg", &cs_num);
>> +	if (cs_num >= STM32_MAX_NORCHIP)
>> +		return -EINVAL;
>> +
>> +	of_property_read_u32(np, "spi-max-frequency", &max_rate);
>> +	if (!max_rate)
>> +		return -EINVAL;
>> +
>> +	presc = DIV_ROUND_UP(qspi->clk_rate, max_rate) - 1;
>> +
>> +	if (of_property_read_u32(np, "spi-rx-bus-width", &width))
>> +		width = 1;
>> +
>> +	if (width == 4)
>> +		flash_read = SPI_NOR_QUAD;
>> +	else if (width == 2)
>> +		flash_read = SPI_NOR_DUAL;
>> +	else if (width == 1)
>> +		flash_read = SPI_NOR_NORMAL;
>> +	else
>> +		return -EINVAL;
>> +
>> +	flash = &qspi->flash[cs_num];
>> +	flash->qspi = qspi;
>> +	flash->cs = cs_num;
>> +	flash->presc = presc;
>> +
>> +	flash->nor.dev = qspi->dev;
>> +	spi_nor_set_flash_node(&flash->nor, np);
>> +	flash->nor.priv = flash;
>> +	mtd = &flash->nor.mtd;
>> +	mtd->priv = &flash->nor;
>> +
>> +	flash->nor.read = stm32_qspi_read;
>> +	flash->nor.write = stm32_qspi_write;
>> +	flash->nor.erase = stm32_qspi_erase;
>> +	flash->nor.read_reg = stm32_qspi_read_reg;
>> +	flash->nor.write_reg = stm32_qspi_write_reg;
>> +	flash->nor.prepare = stm32_qspi_prep;
>> +	flash->nor.unprepare = stm32_qspi_unprep;
>> +
>> +	writel_relaxed(LPTR_DFT_TIMEOUT, qspi->io_base + QUADSPI_LPTR);
>> +
>> +	writel_relaxed(CR_PRESC(presc) | CR_FTHRES(3) | CR_TCEN | CR_SSHIFT
>> +		       | CR_EN, qspi->io_base + QUADSPI_CR);
>> +
>> +	/*
>> +	 * in stm32 qspi controller, QUADSPI_DCR register has a fsize field
>> +	 * which define the size of nor flash.
>> +	 * if fsize is NULL, the controller can't sent spi-nor command.
>> +	 * set a temporary value just to discover the nor flash with
>> +	 * "spi_nor_scan". After, the right value (mtd->size) can be set.
>> +	 */
> Is 25 the smallest value ? Use a macro for this ...
25 is an arbitrary choice, I will define a smallest value
>
>> +	flash->fsize = 25;
>> +
>> +	ret = spi_nor_scan(&flash->nor, NULL, flash_read);
>> +	if (ret) {
>> +		dev_err(qspi->dev, "device scan failed\n");
>> +		return ret;
>> +	}
>> +
>> +	/* number of bytes in Flash memory = 2^[FSIZE+1] */
>> +	flash->fsize = __fls(mtd->size) - 1;
>> +
>> +	writel_relaxed(DCR_CSHT(1), qspi->io_base + QUADSPI_DCR);
>> +
>> +	ret = mtd_device_register(mtd, NULL, 0);
>> +	if (ret) {
>> +		dev_err(qspi->dev, "mtd device parse failed\n");
>> +		return ret;
>> +	}
>> +
>> +	dev_dbg(qspi->dev, "read mm:%s cs:%d bus:%d\n",
>> +		qspi->read_mode == CCR_FMODE_MM ? "yes" : "no", cs_num, width);
>> +
>> +	return 0;
>> +}
> [...]
>