Subject: Re: [PATCH v2 2/2] mtd: spi-nor: add driver for STM32 quad spi flash
 controller
To: Ludovic BARRE <ludovic.barre@st.com>,
        Cyrille Pitchen <cyrille.pitchen@atmel.com>
References: <1490979724-10905-1-git-send-email-ludovic.Barre@st.com>
 <1490979724-10905-3-git-send-email-ludovic.Barre@st.com>
 <5ec38e39-661d-8a83-4168-b9f3d986bcd1@gmail.com>
 <601e2aa5-7cd3-34fb-660e-359f2a016b65@st.com>
Cc: David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Boris Brezillon <boris.brezillon@free-electrons.com>,
        Richard Weinberger <richard@nod.at>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        Rob Herring <robh+dt@kernel.org>, linux-mtd@lists.infradead.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
From: Marek Vasut <marek.vasut@gmail.com>
Message-ID: <9a0c5f8e-01dc-3d2b-5ebb-069752594e8e@gmail.com>
Date: Mon, 10 Apr 2017 18:15:55 +0200
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On 04/10/2017 11:08 AM, Ludovic BARRE wrote:
> 
> 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

Well, as you like, but I think it does make sense to just make it flat.

>>> +    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.

Hmmm, (rhetorical question) then why do we even use loff_t in the
framework ?

Anyway, this is no problem then.

>>> +    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.

Yep

>>> +    }
>>> +
>>> +    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

Cool, thanks!

-- 
Best regards,
Marek Vasut