Re: [PATCH 3/3] iio: temperature: ltc2983: support more parts

Jonathan Cameron
2022-10-14T15:45:05Z

On Fri, 14 Oct 2022 15:37:24 +0300
Cosmin Tanislav <demonsingur@gmail.com> wrote:

> From: Cosmin Tanislav <cosmin.tanislav@analog.com>
>
> Add support for the following parts:
> * LTC2984
> * LTC2986
> * LTM2985
>
> The LTC2984 is a variant of the LTC2983 with EEPROM.
> The LTC2986 is a variant of the LTC2983 with only 10 channels,
> EEPROM and support for active analog temperature sensors.
> The LTM2985 is software-compatible with the LTC2986.
>
> Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>

...

Hi Cosmin,

Looks good except, I think we are still in the position that
regmap for spi doesn't guarantee to bounce buffer the bulk accesses
(last time I checked it actually did do so, but before that it didn't
and there are obvious optimizations to take it back to not doing so -
IRC Mark Brown's answer was we shouldn't rely on it..)

Anyhow, the existing driver has instances of this so its no worse
but we should really clean those up.

Jonathan

>
> +static int ltc2983_eeprom_cmd(struct ltc2983_data *st, unsigned int cmd,
> + unsigned int wait_time, unsigned int status_reg,
> + unsigned long status_fail_mask)
> +{
> + __be32 bval = cpu_to_be32(LTC2983_EEPROM_KEY);
> + unsigned long time;
> + unsigned int val;
> + int ret;
> +
> + ret = regmap_bulk_write(st->regmap, LTC2983_EEPROM_KEY_REG, &bval,
> + sizeof(bval));

SPI device and I was clearly dozing on existing driver but normally
we avoid assuming that regmap will always use a bounce buffer for bulk
accessors. Hence this should be a DMA safe buffer.

> + if (ret)
> + return ret;
> +
> + reinit_completion(&st->completion);
> +
> + ret = regmap_write(st->regmap, LTC2983_STATUS_REG,
> + LTC2983_STATUS_START(true) | cmd);
> + if (ret)
> + return ret;
> +
> + time = wait_for_completion_timeout(&st->completion,
> + msecs_to_jiffies(wait_time));
> + if (!time) {
> + dev_err(&st->spi->dev, "EEPROM command timed out\n");
> + return -ETIMEDOUT;
> + }
> +
> + ret = regmap_read(st->regmap, status_reg, &val);
> + if (ret)
> + return ret;
> +
> + if (val & status_fail_mask) {
> + dev_err(&st->spi->dev, "EEPROM command failed: 0x%02X\n", val);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +