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SubjectRe: [PATCH] eeprom: at25: Convert the driver to the spi-mem interface
Hi Boris,

On Sat, Mar 30, 2019 at 3:16 PM Boris Brezillon
<boris.brezillon@collabora.com> wrote:
> The AT25 protocol fits pretty well in the spi-mem model. Convert the
> at25 spi driver to a spi-mem driver and use the dirmap API instead of
> forging SPI messages manually.
> This makes the driver compatible with spi-mem-only controllers
> (controllers implementing only the spi_mem ops).

Thanks for your patch!

> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

> --- a/drivers/misc/eeprom/at25.c
> +++ b/drivers/misc/eeprom/at25.c

> @@ -63,17 +68,89 @@ struct at25_data {
>
> #define io_limit PAGE_SIZE /* bytes */
>
> +static int at25_create_dirmaps(struct at25_data *at25)
> +{
> + struct spi_mem_dirmap_info info = {
> + .op_tmpl = SPI_MEM_OP(SPI_MEM_OP_CMD(AT25_READ, 1),
> + SPI_MEM_OP_ADDR(at25->addrlen, 0, 1),
> + SPI_MEM_OP_NO_DUMMY,
> + SPI_MEM_OP_DATA_IN(0, NULL, 1)),
> + .offset = 0,
> + .length = at25->chip.byte_len,
> + };
> + struct device *dev = &at25->spimem->spi->dev;
> +
> + if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
> + info.length = 256;

Note that by hardcoding 256 you do loose the ability to support chips
where EE_INSTR_BIT3_IS_ADDR is set, _and_ more than one address byte is
used (i.e. extra bit is A16 or A24).
While the code parsing "address-width" doesn't handle that, the comment
for EE_INSTR_BIT3_IS_ADDR suggests such chips do exist (I doubt it,
though, but you may know better), and the flag can be enabled through
the "at25,addr-mode" property, or through platform_data.

> @@ -82,38 +159,14 @@ static int at25_ee_read(void *priv, unsigned int offset,
> if (unlikely(!count))
> return -EINVAL;
>
> - cp = command;
> -
> - instr = AT25_READ;
> - if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
> - if (offset >= (1U << (at25->addrlen * 8)))
> - instr |= AT25_INSTR_BIT3;
> - *cp++ = instr;
> -
> - /* 8/16/24-bit address is written MSB first */
> - switch (at25->addrlen) {
> - default: /* case 3 */
> - *cp++ = offset >> 16;
> - /* fall through */
> - case 2:
> - *cp++ = offset >> 8;
> - /* fall through */
> - case 1:
> - case 0: /* can't happen: for better codegen */
> - *cp++ = offset >> 0;
> + if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR && offset > 255) {

Loss of support for address bit A16/A24.

> + desc = at25->dirmap.rdesc[1];
> + dirmap_offset = offset - 256;
> + } else {
> + desc = at25->dirmap.rdesc[0];
> + dirmap_offset = offset;
> }

> @@ -158,48 +211,37 @@ static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
> */
> mutex_lock(&at25->lock);
> do {
> + struct spi_mem_dirmap_desc *desc;
> unsigned long timeout, retries;
> unsigned segment;
> - unsigned offset = (unsigned) off;
> - u8 *cp = bounce;
> + unsigned int dirmap_offset;
> int sr;
> - u8 instr;
>
> - *cp = AT25_WREN;
> - status = spi_write(at25->spi, cp, 1);
> + status = at25_wren(at25);
> if (status < 0) {
> - dev_dbg(&at25->spi->dev, "WREN --> %d\n", status);
> + dev_dbg(&at25->spimem->spi->dev, "WREN --> %d\n",
> + status);
> break;
> }
>
> - instr = AT25_WRITE;
> - if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
> - if (offset >= (1U << (at25->addrlen * 8)))
> - instr |= AT25_INSTR_BIT3;
> - *cp++ = instr;
> -
> - /* 8/16/24-bit address is written MSB first */
> - switch (at25->addrlen) {
> - default: /* case 3 */
> - *cp++ = offset >> 16;
> - /* fall through */
> - case 2:
> - *cp++ = offset >> 8;
> - /* fall through */
> - case 1:
> - case 0: /* can't happen: for better codegen */
> - *cp++ = offset >> 0;
> + if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR && off > 255) {

Loss of support for address bit A16/A24.

> + desc = at25->dirmap.wdesc[1];
> + dirmap_offset = off - 256;

Two spaces after minus sign.

> + } else {
> + desc = at25->dirmap.wdesc[0];
> + dirmap_offset = off;
> }

> @@ -211,10 +253,9 @@ static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
> timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
> retries = 0;
> do {
> -
> - sr = spi_w8r8(at25->spi, AT25_RDSR);
> + sr = at25_rdsr(at25);
> if (sr < 0 || (sr & AT25_SR_nRDY)) {
> - dev_dbg(&at25->spi->dev,
> + dev_dbg(&at25->spimem->spi->dev,
> "rdsr --> %d (%02x)\n", sr, sr);

You might want to move the debug print inside the new function
at25_rdsr(), as there's another call plus debug print in at25_probe().

> @@ -328,37 +369,49 @@ static int at25_probe(struct spi_device *spi)
> else if (chip.flags & EE_ADDR3)
> addrlen = 3;
> else {
> - dev_dbg(&spi->dev, "unsupported address type\n");
> + dev_dbg(&spimem->spi->dev, "unsupported address type\n");
> return -EINVAL;
> }
>
> - /* Ping the chip ... the status register is pretty portable,
> - * unlike probing manufacturer IDs. We do expect that system
> - * firmware didn't write it in the past few milliseconds!
> - */
> - sr = spi_w8r8(spi, AT25_RDSR);
> - if (sr < 0 || sr & AT25_SR_nRDY) {
> - dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
> - return -ENXIO;
> - }
> -
> - at25 = devm_kzalloc(&spi->dev, sizeof(struct at25_data), GFP_KERNEL);
> + at25 = devm_kzalloc(&spimem->spi->dev, sizeof(struct at25_data),
> + GFP_KERNEL);
> if (!at25)
> return -ENOMEM;
>
> mutex_init(&at25->lock);
> at25->chip = chip;
> - at25->spi = spi;
> - spi_set_drvdata(spi, at25);
> + at25->spimem = spimem;
> + spi_mem_set_drvdata(spimem, at25);
> at25->addrlen = addrlen;
>
> - at25->nvmem_config.name = dev_name(&spi->dev);
> - at25->nvmem_config.dev = &spi->dev;
> + /*
> + * Can't be allocated with devm_kmalloc() because we need a DMA-safe
> + * buffer.
> + */

That is no longer true as of commit a66d972465d15b1d ("devres: Align
data[] to ARCH_KMALLOC_MINALIGN") in v4.20-rc5, right?

> + at25->scratchbuf = kmalloc(1, GFP_KERNEL);

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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