Re: [PATCH 4/5] mtd: spi-nor: Add driver for Adaptrum Anarion QSPI controller

[Marek Vasut <marek.vasut@gmail.com>]

On 07/31/2017 07:17 PM, Alexandru Gagniuc wrote:
[...]

>>> +++ b/drivers/mtd/spi-nor/anarion-quadspi.c
>>> @@ -0,0 +1,490 @@
>>> +/*
>>> + * Adaptrum Anarion Quad SPI controller driver
>>> + *
>>> + * Copyright (C) 2017, Adaptrum, Inc.
>>> + * (Written by Alexandru Gagniuc <alex.g at adaptrum.com> for
>>> Adaptrum, Inc.)
>>> + * Licensed under the GPLv2 or (at your option) any later version.
>>
>> The GPL boilerplate should be here.
> 
> I chose this form of the boilerplate because it seems to be quite used
> in other places. I am assuming the fatter boilerplate the requirement
> for drivers/mtd, correct?

AFAIK the regular GPLv2 boilerplate is the standard throughout the kernel.

> [snip]
> 
>>> +#define ASPI_CLK_SW_RESET        (1 << 0)
>>
>> BIT(0) , fix globally
> 
> Staged for [PATCH v2].
> 
>>> +#define ASPI_CLK_RESET_BUF        (1 << 1)
>>> +#define ASPI_CLK_RESET_ALL        (ASPI_CLK_SW_RESET |
>>> ASPI_CLK_RESET_BUF)
>>> +#define ASPI_CLK_SPI_MODE3        (1 << 2)
>>> +#define ASPI_CLOCK_DIV_MASK        (0xff << 8)
>>> +#define ASPI_CLOCK_DIV(d)        (((d) << 8) & ASPI_CLOCK_DIV_MASK)
>>> +
>>> +#define ASPI_TIMEOUT_US        100000
>>> +
>>> +#define ASPI_DATA_LEN_MASK        0x3fff
>>> +#define ASPI_MAX_XFER_LEN        (size_t)(ASPI_DATA_LEN_MASK + 1)
>>> +
>>> +#define MODE_IO_X1            (0 << 16)
>>> +#define MODE_IO_X2            (1 << 16)
>>> +#define MODE_IO_X4            (2 << 16)
>>> +#define MODE_IO_SDR_POS_SKEW        (0 << 20)
>>> +#define MODE_IO_SDR_NEG_SKEW        (1 << 20)
>>> +#define MODE_IO_DDR_34_SKEW        (2 << 20)
>>> +#define MODE_IO_DDR_PN_SKEW        (3 << 20)
>>> +#define MODE_IO_DDR_DQS            (5 << 20)
>>> +
>>> +#define ASPI_STATUS_BUSY            (1 << 2)
>>> +
>>> +/*
>>> + * This mask does not match reality. Get over it:
>>
>> What is this about ?
> 
> Each stage of the QSPI chain has two registers. The second register has
> a bitfield which takes in the length of the stage. For example, for
> DATA2, we can set the length up to 0x4000, but for ADDR2, we can only
> set a max of 4 bytes. I wrote this comment as a reminder to myself to be
> careful about using this mask. I'll rephrase the comment for [v2]

Please do.

>>> + * DATA2:    0x3fff
>>> + * CMD2:    0x0003
>>> + * ADDR2:    0x0007
>>> + * PERF2:    0x0000
>>> + * HI_Z:    0x003f
>>> + * BCNT:    0x0007
>>> + */
>>> +#define CHAIN_LEN(x)        ((x - 1) & ASPI_DATA_LEN_MASK)
>>> +
>>> +struct anarion_qspi {
>>> +    struct        spi_nor nor;
>>> +    struct        device *dev;
>>> +    uintptr_t    regbase;
>>
>> Should be void __iomem * I guess ?
> 
> I chose uintptr_t as opposed to void *, because arithmetic on void * is
> not valid in C. What is the right answer hen, without risking undefined
> behavior?

What sort of arithmetic ? It's perfectly valid in general ...

>>> +    uintptr_t    xipbase;
>>> +    uint32_t    xfer_mode_cmd;
>>
>> u32 etc, fix globally, this is not userspace.
> 
> From coding-style, section 5.(d), my understanding is that
> "Linux-specific u8/u16/u32/u64 types [...] are not mandatory in new
> code". Most of the code in this driver is shared between Linux, u-boot,
> openocd, ASIC validation tests, and manufacturing tests. Unlike,
> shortint types, stdint types are available in all cases.
> 
> Therefore, having to use a different set of primitive types makes code
> sharing much more difficult, and increases the maintenance burden, hence
> the strong preference for standard types. Is this reasonable?

The uXX is still prevalent in drivers/mtd/ according to git grep , so
I'd stick with that. Using uXX in U-Boot is perfectly fine and in fact
recommended.

> [snip]
> 
>>> +static void aspi_drain_fifo(struct anarion_qspi *aspi, uint8_t *buf,
>>> size_t len)
>>> +{
>>> +    uint32_t data;
>>
>> Is this stuff below something like ioread32_rep() ?
>>
>>> +    aspi_write_reg(aspi, ASPI_REG_BYTE_COUNT, sizeof(uint32_t));
>>> +    while (len >= 4) {
>>> +        data = aspi_read_reg(aspi, ASPI_REG_DATA1);
>>> +        memcpy(buf, &data, sizeof(data));
>>> +        buf += 4;
>>> +        len -= 4;
>>> +    }
> 
> That is very similar to ioread32_rep, yes. I kept this as for the
> reasons outlined above, but changing this to _rep() seems innocent enough.

What reason ?

>>> +    if (len) {
>>> +        aspi_write_reg(aspi, ASPI_REG_BYTE_COUNT, len);
>>> +        data = aspi_read_reg(aspi, ASPI_REG_DATA1);
>>> +        memcpy(buf, &data, len);
>>> +    }
>>> +}

[...]

>>> +    switch (nor->flash_read) {
>>> +    default:        /* Fall through */
>>
>> This will break once we add OSPI support ...
> 
> Ooh, I see the API here has changed significantly from the 4.9 LTS
> branch where we originally developed the driver.I will add and test
> normal and FAST_READ support, but I won't have the bandwidth to test
> other modes yet. Those will have to remain as a TODO.

Sigh, please be so kind and use -next for your development next time ...

>>> +    case SPI_NOR_NORMAL:
>>> +        aspi->num_hi_z_clocks = nor->read_dummy;
>>> +        aspi->xfer_mode_cmd = MODE_IO_X1;
>>> +        aspi->xfer_mode_addr = MODE_IO_X1;
>>> +        aspi->xfer_mode_data = MODE_IO_X1;
>>> +        break;
>>> +    case SPI_NOR_FAST:
>>> +        aspi->num_hi_z_clocks = nor->read_dummy;
>>> +        aspi->xfer_mode_cmd = MODE_IO_X1;
>>> +        aspi->xfer_mode_addr = MODE_IO_X1;
>>> +        aspi->xfer_mode_data = MODE_IO_X1;
>>> +        break;
>>> +    case SPI_NOR_DUAL:
>>> +        aspi->num_hi_z_clocks = nor->read_dummy;
>>> +        aspi->xfer_mode_cmd = MODE_IO_X1;
>>> +        aspi->xfer_mode_addr = MODE_IO_X1;
>>> +        aspi->xfer_mode_data = MODE_IO_X2;
>>> +        break;
>>> +    case SPI_NOR_QUAD:
>>> +        aspi->num_hi_z_clocks = nor->read_dummy;
>>> +        aspi->xfer_mode_cmd = MODE_IO_X1;
>>> +        aspi->xfer_mode_addr = MODE_IO_X1;
>>> +        aspi->xfer_mode_data = MODE_IO_X4;
>>> +        break;
>>> +    }
>>> +
>>> +    aspi_setup_xip_read_chain(aspi, nor);
>>> +
>>> +    mtd_device_register(&aspi->nor.mtd, NULL, 0);
>>> +
>>> +    return 0;
>>> +}
> 
> [snip]


-- 
Best regards,
Marek Vasut