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SubjectRe: [PATCH 1/2] net: dsa: mv88e6xxx: sleep in _mv88e6xxx_stats_wait
On Fri, Jul 10, 2015 at 12:57:28PM -0400, Vivien Didelot wrote:
> The current _mv88e6xxx_stats_wait function does not sleep while testing
> the stats busy bit. Fix this by using the generic _mv88e6xxx_wait
> function.
>
> Note that it requires to move _mv88e6xxx_wait on top of
> _mv88e6xxx_stats_wait to avoid undefined reference compilation error.
>
> Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
> ---
> drivers/net/dsa/mv88e6xxx.c | 52 +++++++++++++++++++--------------------------
> 1 file changed, 22 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/net/dsa/mv88e6xxx.c b/drivers/net/dsa/mv88e6xxx.c
> index f6c7409..7753db1 100644
> --- a/drivers/net/dsa/mv88e6xxx.c
> +++ b/drivers/net/dsa/mv88e6xxx.c
> @@ -557,19 +557,31 @@ static bool mv88e6xxx_6352_family(struct dsa_switch *ds)
> return false;
> }
>
> +/* Must be called with SMI lock held */
> +static int _mv88e6xxx_wait(struct dsa_switch *ds, int reg, int offset,
> + u16 mask)
> +{
> + unsigned long timeout = jiffies + HZ / 10;
> +
> + while (time_before(jiffies, timeout)) {
> + int ret;
> +
> + ret = _mv88e6xxx_reg_read(ds, reg, offset);
> + if (ret < 0)
> + return ret;
> + if (!(ret & mask))
> + return 0;
> +
> + usleep_range(1000, 2000);
> + }
> + return -ETIMEDOUT;
> +}
> +
> /* Must be called with SMI mutex held */
> static int _mv88e6xxx_stats_wait(struct dsa_switch *ds)
> {
> - int ret;
> - int i;
> -
> - for (i = 0; i < 10; i++) {
> - ret = _mv88e6xxx_reg_read(ds, REG_GLOBAL, GLOBAL_STATS_OP);
> - if ((ret & GLOBAL_STATS_OP_BUSY) == 0)
> - return 0;
> - }

Hi Vivien,

is this really beneficial and/or needed ? It adds at least 1ms delay
to a loop which did not have any delay at all unless the register
read itself was sleeping. Is the original function seen to return
a timeout error under some circumstances ?

Thanks,
Guenter


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