[U-Boot] [PATCH v3 1/5] lib: Add wait_for_bit

Simon Glass
2016-01-20T04:34:40Z

Hi,

On 27 December 2015 at 10:28, Mateusz Kulikowski
<mateusz.kulikowski@gmail.com> wrote:
> Add function to poll register waiting for specific bit(s).
> Similar functions are implemented in few drivers - they are almost
> identical and can be generalized.
> Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
> ---
>
> include/wait_bit.h | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 71 insertions(+)
> create mode 100644 include/wait_bit.h
>

Sorry I only just saw this, but thought I'd make a few comments.

> diff --git a/include/wait_bit.h b/include/wait_bit.h
> new file mode 100644
> index 0000000..4867ced
> --- /dev/null
> +++ b/include/wait_bit.h
> @@ -0,0 +1,71 @@
> +/*
> + * Wait for bit with timeout and ctrlc
> + *
> + * (C) Copyright 2015 Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0+
> + */
> +
> +#ifndef __WAIT_BIT_H
> +#define __WAIT_BIT_H
> +
> +#include <common.h>
> +#include <console.h>
> +#include <asm/errno.h>
> +#include <asm/io.h>
> +
> +/**
> + * wait_for_bit() waits for bit set/cleared in register
> + *
> + * Function polls register waiting for specific bit(s) change
> + * (either 0->1 or 1->0). It can fail under two conditions:
> + * - Timeout
> + * - User interaction (CTRL-C)
> + * Function succeeds only if all bits of masked register are set/cleared
> + * (depending on set option).
> + *
> + * @param prefix Prefix added to timeout messagge (message visible only
> + * with debug enabled)
> + * @param reg Register that will be read (using readl())
> + * @param mask Bit(s) of register that must be active
> + * @param set Selects wait condition (bit set or clear)
> + * @param timeout Timeout (in miliseconds)
> + * @param breakable Enables CTRL-C interruption
> + * @return 0 on success, -ETIMEDOUT or -EINTR on failure
> + */
> +static inline int wait_for_bit(const char *prefix, const u32 *reg,
> + const u32 mask, const bool set,
> + const unsigned int timeout,

timeout_ms would be more obvious

> + const bool breakable)

Wow this is a pretty big inline function.

Do you need the 'prefix' parameter? It seems that the callers print
messages anyway. How about adding a flags word for @set and
@breakable? Those params could then be combined, and you end up with 4
parameters instead of 6.

> +{
> + u32 val;
> + unsigned long start = get_timer(0);
> +
> + while (1) {
> + val = readl(reg);
> +
> + if (!set)
> + val = ~val;
> +
> + if ((val & mask) == mask)
> + return 0;
> +
> + if (get_timer(start) > timeout)
> + break;
> +
> + if (breakable && ctrlc()) {
> + puts("Abort\n");

This is bad if used from drivers. We try not to output things. It it necessary?

> + return -EINTR;
> + }
> +
> + udelay(1);
> + }
> +
> + debug("%s: Timeout (reg=%p mask=%08x wait_set=%i)\n", prefix, reg, mask,
> + set);
> +
> + return -ETIMEDOUT;
> +}
> +
> +
> +#endif
> --
> 2.5.0
>
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