linux-kernel - Re: [PATCH v2] regmap: add iopoll-like atomic polling macro

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Message-ID: <9dced231-0392-5ac2-d4a2-e176e8cebba5@nvidia.com>
Date:   Thu, 9 Jan 2020 10:35:19 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     <broonie@...nel.org>
CC:     <jonathanh@...dia.com>, <linux-kernel@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v2] regmap: add iopoll-like atomic polling macro


On 1/9/2020 10:31 AM, Sameer Pujar wrote:
> This patch adds a macro 'regmap_read_poll_timeout_atomic' that works
> similar to 'readx_poll_timeout_atomic' defined in linux/iopoll.h; This
> is atomic version of already available 'regmap_read_poll_timeout' macro.
>
> It should be noted that above atomic macro cannot be used by all regmaps.
> If the regmap is set up for atomic use (flat or no cache and MMIO) then
> only it can use.
>
> Signed-off-by: Sameer Pujar <spujar@...dia.com>
> ---
>   include/linux/regmap.h | 45 +++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 45 insertions(+)
>
> diff --git a/include/linux/regmap.h b/include/linux/regmap.h
> index dfe493a..aaf0ed1 100644
> --- a/include/linux/regmap.h
> +++ b/include/linux/regmap.h
> @@ -119,6 +119,10 @@ struct reg_sequence {
>    * from atomic context if sleep_us or timeout_us are used.
>    *
>    * This is modelled after the readx_poll_timeout macros in linux/iopoll.h.
> + *
> + * Note: In general regmap cannot be used in atomic context. If you want to use
> + * this macro then first setup your regmap for atomic use (flat or no cache
> + * and MMIO regmap).

oops! Sorry!
Wrong place, will fix in next revision.

>    */
>   #define regmap_read_poll_timeout(map, addr, val, cond, sleep_us, timeout_us) \
>   ({ \
> @@ -145,6 +149,47 @@ struct reg_sequence {
>   })
>   
>   /**
> + * regmap_read_poll_timeout_atomic - Poll until a condition is met or a timeout occurs
> + *
> + * @map: Regmap to read from
> + * @addr: Address to poll
> + * @val: Unsigned integer variable to read the value into
> + * @cond: Break condition (usually involving @val)
> + * @delay_us: Time to udelay between reads in us (0 tight-loops).
> + *            Should be less than ~10us since udelay is used
> + *            (see Documentation/timers/timers-howto.rst).
> + * @timeout_us: Timeout in us, 0 means never timeout
> + *
> + * Returns 0 on success and -ETIMEDOUT upon a timeout or the regmap_read
> + * error return value in case of a error read. In the two former cases,
> + * the last read value at @addr is stored in @val.
> + *
> + * This is modelled after the readx_poll_timeout_atomic macros in linux/iopoll.h.
> + */
> +#define regmap_read_poll_timeout_atomic(map, addr, val, cond, delay_us, timeout_us) \
> +({ \
> +	u64 __timeout_us = (timeout_us); \
> +	unsigned long __delay_us = (delay_us); \
> +	ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
> +	int __ret; \
> +	for (;;) { \
> +		__ret = regmap_read((map), (addr), &(val)); \
> +		if (__ret) \
> +			break; \
> +		if (cond) \
> +			break; \
> +		if ((__timeout_us) && \
> +		    ktime_compare(ktime_get(), __timeout) > 0) { \
> +			__ret = regmap_read((map), (addr), &(val)); \
> +			break; \
> +		} \
> +		if (__delay_us) \
> +			udelay(__delay_us); \
> +	} \
> +	__ret ?: ((cond) ? 0 : -ETIMEDOUT); \
> +})
> +
> +/**
>    * regmap_field_read_poll_timeout - Poll until a condition is met or timeout
>    *
>    * @field: Regmap field to read from