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

[Marek Vasut]

On 04/10/2017 06:52 PM, Ludovic BARRE wrote:
> hi Marek
> 
> tomorrow, I send a v3 with your/Rob reviews.

Super, thanks! I'll be pretty busy till Friday, so please keep in mind
the final review might take a bit.

> BR
> 
> Ludo
> 
> 
> On 04/10/2017 06:15 PM, Marek Vasut wrote:
>> 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@xxxxxx>
>>>>>
>>>>> 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@xxxxxx>
>>>>> ---
>>>>>    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.
> In fact, the loff_t 64 bit come from mtd interface
> (needed to address biggest device constraint) but not needed for spi-nor
> devices.
>>>>> +    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