* [PATCH net-next] net: dsa: mt7530: support setting ageing time
@ 2020-12-08 7:00 ` DENG Qingfang
0 siblings, 0 replies; 12+ messages in thread
From: DENG Qingfang @ 2020-12-08 7:00 UTC (permalink / raw)
To: netdev, linux-mediatek, Sean Wang, Landen Chao, Andrew Lunn,
Vivien Didelot, Florian Fainelli, Vladimir Oltean,
David S . Miller, Jakub Kicinski, Matthias Brugger, Russell King
Cc: Frank Wunderlich
MT7530 has a global address age control register, so use it to set
ageing time.
The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
---
drivers/net/dsa/mt7530.c | 41 ++++++++++++++++++++++++++++++++++++++++
drivers/net/dsa/mt7530.h | 13 +++++++++++++
2 files changed, 54 insertions(+)
diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 6408402a44f5..99bf8fed6536 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -870,6 +870,46 @@ mt7530_get_sset_count(struct dsa_switch *ds, int port, int sset)
return ARRAY_SIZE(mt7530_mib);
}
+static int
+mt7530_set_ageing_time(struct dsa_switch *ds, unsigned int msecs)
+{
+ struct mt7530_priv *priv = ds->priv;
+ unsigned int secs = msecs / 1000;
+ unsigned int tmp_age_count;
+ unsigned int error = -1;
+ unsigned int age_count;
+ unsigned int age_unit;
+
+ /* Applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds */
+ if (secs < 1 || secs > (AGE_CNT_MAX + 1) * (AGE_UNIT_MAX + 1))
+ return -ERANGE;
+
+ /* iterate through all possible age_count to find the closest pair */
+ for (tmp_age_count = 0; tmp_age_count <= AGE_CNT_MAX; ++tmp_age_count) {
+ unsigned int tmp_age_unit = secs / (tmp_age_count + 1) - 1;
+
+ if (tmp_age_unit <= AGE_UNIT_MAX) {
+ unsigned int tmp_error = secs -
+ (tmp_age_count + 1) * (tmp_age_unit + 1);
+
+ /* found a closer pair */
+ if (error > tmp_error) {
+ error = tmp_error;
+ age_count = tmp_age_count;
+ age_unit = tmp_age_unit;
+ }
+
+ /* found the exact match, so break the loop */
+ if (!error)
+ break;
+ }
+ }
+
+ mt7530_write(priv, MT7530_AAC, AGE_CNT(age_count) | AGE_UNIT(age_unit));
+
+ return 0;
+}
+
static void mt7530_setup_port5(struct dsa_switch *ds, phy_interface_t interface)
{
struct mt7530_priv *priv = ds->priv;
@@ -2564,6 +2604,7 @@ static const struct dsa_switch_ops mt7530_switch_ops = {
.phy_write = mt753x_phy_write,
.get_ethtool_stats = mt7530_get_ethtool_stats,
.get_sset_count = mt7530_get_sset_count,
+ .set_ageing_time = mt7530_set_ageing_time,
.port_enable = mt7530_port_enable,
.port_disable = mt7530_port_disable,
.port_change_mtu = mt7530_port_change_mtu,
diff --git a/drivers/net/dsa/mt7530.h b/drivers/net/dsa/mt7530.h
index ee3523a7537e..32d8969b3ace 100644
--- a/drivers/net/dsa/mt7530.h
+++ b/drivers/net/dsa/mt7530.h
@@ -161,6 +161,19 @@ enum mt7530_vlan_egress_attr {
MT7530_VLAN_EGRESS_STACK = 3,
};
+/* Register for address age control */
+#define MT7530_AAC 0xa0
+/* Disable ageing */
+#define AGE_DIS BIT(20)
+/* Age count */
+#define AGE_CNT_MASK GENMASK(19, 12)
+#define AGE_CNT_MAX 0xff
+#define AGE_CNT(x) (AGE_CNT_MASK & ((x) << 12))
+/* Age unit */
+#define AGE_UNIT_MASK GENMASK(11, 0)
+#define AGE_UNIT_MAX 0xfff
+#define AGE_UNIT(x) (AGE_UNIT_MASK & (x))
+
/* Register for port STP state control */
#define MT7530_SSP_P(x) (0x2000 + ((x) * 0x100))
#define FID_PST(x) ((x) & 0x3)
--
2.25.1
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply related [flat|nested] 12+ messages in thread* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
2020-12-08 7:00 ` DENG Qingfang
@ 2020-12-08 14:17 ` Andrew Lunn
-1 siblings, 0 replies; 12+ messages in thread
From: Andrew Lunn @ 2020-12-08 14:17 UTC (permalink / raw)
To: DENG Qingfang
Cc: netdev, linux-mediatek, Sean Wang, Landen Chao, Vivien Didelot,
Florian Fainelli, Vladimir Oltean, David S . Miller,
Jakub Kicinski, Matthias Brugger, Russell King, Frank Wunderlich
On Tue, Dec 08, 2020 at 03:00:28PM +0800, DENG Qingfang wrote:
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Andrew
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
@ 2020-12-08 14:17 ` Andrew Lunn
0 siblings, 0 replies; 12+ messages in thread
From: Andrew Lunn @ 2020-12-08 14:17 UTC (permalink / raw)
To: DENG Qingfang
Cc: Landen Chao, Florian Fainelli, Frank Wunderlich, netdev,
Sean Wang, Russell King, David S . Miller, linux-mediatek,
Matthias Brugger, Jakub Kicinski, Vladimir Oltean,
Vivien Didelot
On Tue, Dec 08, 2020 at 03:00:28PM +0800, DENG Qingfang wrote:
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Andrew
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
2020-12-08 7:00 ` DENG Qingfang
@ 2020-12-08 20:56 ` Vladimir Oltean
-1 siblings, 0 replies; 12+ messages in thread
From: Vladimir Oltean @ 2020-12-08 20:56 UTC (permalink / raw)
To: DENG Qingfang
Cc: netdev, linux-mediatek, Sean Wang, Landen Chao, Andrew Lunn,
Vivien Didelot, Florian Fainelli, David S . Miller,
Jakub Kicinski, Matthias Brugger, Russell King, Frank Wunderlich
On Tue, Dec 08, 2020 at 03:00:28PM +0800, DENG Qingfang wrote:
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
> ---
> drivers/net/dsa/mt7530.c | 41 ++++++++++++++++++++++++++++++++++++++++
> drivers/net/dsa/mt7530.h | 13 +++++++++++++
> 2 files changed, 54 insertions(+)
>
> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> index 6408402a44f5..99bf8fed6536 100644
> --- a/drivers/net/dsa/mt7530.c
> +++ b/drivers/net/dsa/mt7530.c
> @@ -870,6 +870,46 @@ mt7530_get_sset_count(struct dsa_switch *ds, int port, int sset)
> return ARRAY_SIZE(mt7530_mib);
> }
>
> +static int
> +mt7530_set_ageing_time(struct dsa_switch *ds, unsigned int msecs)
> +{
> + struct mt7530_priv *priv = ds->priv;
> + unsigned int secs = msecs / 1000;
> + unsigned int tmp_age_count;
> + unsigned int error = -1;
> + unsigned int age_count;
> + unsigned int age_unit;
> +
> + /* Applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds */
> + if (secs < 1 || secs > (AGE_CNT_MAX + 1) * (AGE_UNIT_MAX + 1))
> + return -ERANGE;
> +
> + /* iterate through all possible age_count to find the closest pair */
> + for (tmp_age_count = 0; tmp_age_count <= AGE_CNT_MAX; ++tmp_age_count) {
> + unsigned int tmp_age_unit = secs / (tmp_age_count + 1) - 1;
> +
> + if (tmp_age_unit <= AGE_UNIT_MAX) {
> + unsigned int tmp_error = secs -
> + (tmp_age_count + 1) * (tmp_age_unit + 1);
> +
> + /* found a closer pair */
> + if (error > tmp_error) {
> + error = tmp_error;
> + age_count = tmp_age_count;
> + age_unit = tmp_age_unit;
> + }
I feel that the error calculation is just snake oil. This would be enough:
if (tmp_age_unit <= AGE_UNIT_MAX)
break;
Explanation:
You are given a number X, and must find A and B such that the error
E = |(A x B) - X| should be minimum, with
1 <= A <= A_max
1 <= B <= B_max
It is logical to try with A=1 first. If X / A <= B_max, then of course,
B = X / 1, and the error E is 0.
If that doesn't work out, and B > B_max, then you go to A=2. That gives
you another B = X / 2, and the error E is 1. You check again if B <=
B_max. If it is, that's your answer. B = X / 2, with an error E of 1.
You get my point. Iterating ascendingly through A, and calculating B as
X / A, already gives you the smallest error as soon as it satisfies the
B <= B_max requirement.
> +
> + /* found the exact match, so break the loop */
> + if (!error)
> + break;
> + }
> + }
> +
> + mt7530_write(priv, MT7530_AAC, AGE_CNT(age_count) | AGE_UNIT(age_unit));
> +
> + return 0;
> +}
> +
> static void mt7530_setup_port5(struct dsa_switch *ds, phy_interface_t interface)
> {
> struct mt7530_priv *priv = ds->priv;
> @@ -2564,6 +2604,7 @@ static const struct dsa_switch_ops mt7530_switch_ops = {
> .phy_write = mt753x_phy_write,
> .get_ethtool_stats = mt7530_get_ethtool_stats,
> .get_sset_count = mt7530_get_sset_count,
> + .set_ageing_time = mt7530_set_ageing_time,
> .port_enable = mt7530_port_enable,
> .port_disable = mt7530_port_disable,
> .port_change_mtu = mt7530_port_change_mtu,
> diff --git a/drivers/net/dsa/mt7530.h b/drivers/net/dsa/mt7530.h
> index ee3523a7537e..32d8969b3ace 100644
> --- a/drivers/net/dsa/mt7530.h
> +++ b/drivers/net/dsa/mt7530.h
> @@ -161,6 +161,19 @@ enum mt7530_vlan_egress_attr {
> MT7530_VLAN_EGRESS_STACK = 3,
> };
>
> +/* Register for address age control */
> +#define MT7530_AAC 0xa0
> +/* Disable ageing */
> +#define AGE_DIS BIT(20)
> +/* Age count */
> +#define AGE_CNT_MASK GENMASK(19, 12)
> +#define AGE_CNT_MAX 0xff
> +#define AGE_CNT(x) (AGE_CNT_MASK & ((x) << 12))
> +/* Age unit */
> +#define AGE_UNIT_MASK GENMASK(11, 0)
> +#define AGE_UNIT_MAX 0xfff
> +#define AGE_UNIT(x) (AGE_UNIT_MASK & (x))
> +
> /* Register for port STP state control */
> #define MT7530_SSP_P(x) (0x2000 + ((x) * 0x100))
> #define FID_PST(x) ((x) & 0x3)
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
@ 2020-12-08 20:56 ` Vladimir Oltean
0 siblings, 0 replies; 12+ messages in thread
From: Vladimir Oltean @ 2020-12-08 20:56 UTC (permalink / raw)
To: DENG Qingfang
Cc: Andrew Lunn, Landen Chao, Florian Fainelli, Frank Wunderlich,
netdev, Sean Wang, Russell King, David S . Miller,
linux-mediatek, Matthias Brugger, Jakub Kicinski, Vivien Didelot
On Tue, Dec 08, 2020 at 03:00:28PM +0800, DENG Qingfang wrote:
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
> ---
> drivers/net/dsa/mt7530.c | 41 ++++++++++++++++++++++++++++++++++++++++
> drivers/net/dsa/mt7530.h | 13 +++++++++++++
> 2 files changed, 54 insertions(+)
>
> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> index 6408402a44f5..99bf8fed6536 100644
> --- a/drivers/net/dsa/mt7530.c
> +++ b/drivers/net/dsa/mt7530.c
> @@ -870,6 +870,46 @@ mt7530_get_sset_count(struct dsa_switch *ds, int port, int sset)
> return ARRAY_SIZE(mt7530_mib);
> }
>
> +static int
> +mt7530_set_ageing_time(struct dsa_switch *ds, unsigned int msecs)
> +{
> + struct mt7530_priv *priv = ds->priv;
> + unsigned int secs = msecs / 1000;
> + unsigned int tmp_age_count;
> + unsigned int error = -1;
> + unsigned int age_count;
> + unsigned int age_unit;
> +
> + /* Applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds */
> + if (secs < 1 || secs > (AGE_CNT_MAX + 1) * (AGE_UNIT_MAX + 1))
> + return -ERANGE;
> +
> + /* iterate through all possible age_count to find the closest pair */
> + for (tmp_age_count = 0; tmp_age_count <= AGE_CNT_MAX; ++tmp_age_count) {
> + unsigned int tmp_age_unit = secs / (tmp_age_count + 1) - 1;
> +
> + if (tmp_age_unit <= AGE_UNIT_MAX) {
> + unsigned int tmp_error = secs -
> + (tmp_age_count + 1) * (tmp_age_unit + 1);
> +
> + /* found a closer pair */
> + if (error > tmp_error) {
> + error = tmp_error;
> + age_count = tmp_age_count;
> + age_unit = tmp_age_unit;
> + }
I feel that the error calculation is just snake oil. This would be enough:
if (tmp_age_unit <= AGE_UNIT_MAX)
break;
Explanation:
You are given a number X, and must find A and B such that the error
E = |(A x B) - X| should be minimum, with
1 <= A <= A_max
1 <= B <= B_max
It is logical to try with A=1 first. If X / A <= B_max, then of course,
B = X / 1, and the error E is 0.
If that doesn't work out, and B > B_max, then you go to A=2. That gives
you another B = X / 2, and the error E is 1. You check again if B <=
B_max. If it is, that's your answer. B = X / 2, with an error E of 1.
You get my point. Iterating ascendingly through A, and calculating B as
X / A, already gives you the smallest error as soon as it satisfies the
B <= B_max requirement.
> +
> + /* found the exact match, so break the loop */
> + if (!error)
> + break;
> + }
> + }
> +
> + mt7530_write(priv, MT7530_AAC, AGE_CNT(age_count) | AGE_UNIT(age_unit));
> +
> + return 0;
> +}
> +
> static void mt7530_setup_port5(struct dsa_switch *ds, phy_interface_t interface)
> {
> struct mt7530_priv *priv = ds->priv;
> @@ -2564,6 +2604,7 @@ static const struct dsa_switch_ops mt7530_switch_ops = {
> .phy_write = mt753x_phy_write,
> .get_ethtool_stats = mt7530_get_ethtool_stats,
> .get_sset_count = mt7530_get_sset_count,
> + .set_ageing_time = mt7530_set_ageing_time,
> .port_enable = mt7530_port_enable,
> .port_disable = mt7530_port_disable,
> .port_change_mtu = mt7530_port_change_mtu,
> diff --git a/drivers/net/dsa/mt7530.h b/drivers/net/dsa/mt7530.h
> index ee3523a7537e..32d8969b3ace 100644
> --- a/drivers/net/dsa/mt7530.h
> +++ b/drivers/net/dsa/mt7530.h
> @@ -161,6 +161,19 @@ enum mt7530_vlan_egress_attr {
> MT7530_VLAN_EGRESS_STACK = 3,
> };
>
> +/* Register for address age control */
> +#define MT7530_AAC 0xa0
> +/* Disable ageing */
> +#define AGE_DIS BIT(20)
> +/* Age count */
> +#define AGE_CNT_MASK GENMASK(19, 12)
> +#define AGE_CNT_MAX 0xff
> +#define AGE_CNT(x) (AGE_CNT_MASK & ((x) << 12))
> +/* Age unit */
> +#define AGE_UNIT_MASK GENMASK(11, 0)
> +#define AGE_UNIT_MAX 0xfff
> +#define AGE_UNIT(x) (AGE_UNIT_MASK & (x))
> +
> /* Register for port STP state control */
> #define MT7530_SSP_P(x) (0x2000 + ((x) * 0x100))
> #define FID_PST(x) ((x) & 0x3)
> --
> 2.25.1
>
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
2020-12-08 20:56 ` Vladimir Oltean
@ 2020-12-08 21:19 ` Vladimir Oltean
-1 siblings, 0 replies; 12+ messages in thread
From: Vladimir Oltean @ 2020-12-08 21:19 UTC (permalink / raw)
To: DENG Qingfang
Cc: netdev, linux-mediatek, Sean Wang, Landen Chao, Andrew Lunn,
Vivien Didelot, Florian Fainelli, David S . Miller,
Jakub Kicinski, Matthias Brugger, Russell King, Frank Wunderlich
On Tue, Dec 08, 2020 at 10:56:21PM +0200, Vladimir Oltean wrote:
> On Tue, Dec 08, 2020 at 03:00:28PM +0800, DENG Qingfang wrote:
> > MT7530 has a global address age control register, so use it to set
> > ageing time.
> >
> > The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
> >
> > Signed-off-by: DENG Qingfang <dqfext@gmail.com>
> > ---
> > drivers/net/dsa/mt7530.c | 41 ++++++++++++++++++++++++++++++++++++++++
> > drivers/net/dsa/mt7530.h | 13 +++++++++++++
> > 2 files changed, 54 insertions(+)
> >
> > diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> > index 6408402a44f5..99bf8fed6536 100644
> > --- a/drivers/net/dsa/mt7530.c
> > +++ b/drivers/net/dsa/mt7530.c
> > @@ -870,6 +870,46 @@ mt7530_get_sset_count(struct dsa_switch *ds, int port, int sset)
> > return ARRAY_SIZE(mt7530_mib);
> > }
> >
> > +static int
> > +mt7530_set_ageing_time(struct dsa_switch *ds, unsigned int msecs)
> > +{
> > + struct mt7530_priv *priv = ds->priv;
> > + unsigned int secs = msecs / 1000;
> > + unsigned int tmp_age_count;
> > + unsigned int error = -1;
> > + unsigned int age_count;
> > + unsigned int age_unit;
> > +
> > + /* Applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds */
> > + if (secs < 1 || secs > (AGE_CNT_MAX + 1) * (AGE_UNIT_MAX + 1))
> > + return -ERANGE;
> > +
> > + /* iterate through all possible age_count to find the closest pair */
> > + for (tmp_age_count = 0; tmp_age_count <= AGE_CNT_MAX; ++tmp_age_count) {
> > + unsigned int tmp_age_unit = secs / (tmp_age_count + 1) - 1;
> > +
> > + if (tmp_age_unit <= AGE_UNIT_MAX) {
> > + unsigned int tmp_error = secs -
> > + (tmp_age_count + 1) * (tmp_age_unit + 1);
> > +
> > + /* found a closer pair */
> > + if (error > tmp_error) {
> > + error = tmp_error;
> > + age_count = tmp_age_count;
> > + age_unit = tmp_age_unit;
> > + }
>
> I feel that the error calculation is just snake oil. This would be enough:
>
> if (tmp_age_unit <= AGE_UNIT_MAX)
> break;
>
> Explanation:
>
> You are given a number X, and must find A and B such that the error
> E = |(A x B) - X| should be minimum, with
> 1 <= A <= A_max
> 1 <= B <= B_max
>
> It is logical to try with A=1 first. If X / A <= B_max, then of course,
> B = X / 1, and the error E is 0.
>
> If that doesn't work out, and B > B_max, then you go to A=2. That gives
> you another B = X / 2, and the error E is 1. You check again if B <=
> B_max. If it is, that's your answer. B = X / 2, with an error E of 1.
>
> You get my point. Iterating ascendingly through A, and calculating B as
> X / A, already gives you the smallest error as soon as it satisfies the
> B <= B_max requirement.
>
> > +
> > + /* found the exact match, so break the loop */
> > + if (!error)
> > + break;
> > + }
> > + }
> > +
> > + mt7530_write(priv, MT7530_AAC, AGE_CNT(age_count) | AGE_UNIT(age_unit));
> > +
> > + return 0;
> > +}
Thinking more about it, it's not snake oil but is actually correct.
Where I was wrong was the division giving you a certain error, but it
actually only gives a maximum error. Other, larger, divisors can still
give you an error of 0.
If the number you're searching for, X, is, say, a multiple of 3 but not
of 2, and is:
B_max * 1 < X < B_max * 2
then exiting the loop at A=2 would give you an error E=1. But if you
continued the loop, then A=3 would have yielded an error E=0, because X
is a multiple of 3 but not of 2. I should probably go and refresh my
basic arithmetic.
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
@ 2020-12-08 21:19 ` Vladimir Oltean
0 siblings, 0 replies; 12+ messages in thread
From: Vladimir Oltean @ 2020-12-08 21:19 UTC (permalink / raw)
To: DENG Qingfang
Cc: Andrew Lunn, Landen Chao, Florian Fainelli, Frank Wunderlich,
netdev, Sean Wang, Russell King, David S . Miller,
linux-mediatek, Matthias Brugger, Jakub Kicinski, Vivien Didelot
On Tue, Dec 08, 2020 at 10:56:21PM +0200, Vladimir Oltean wrote:
> On Tue, Dec 08, 2020 at 03:00:28PM +0800, DENG Qingfang wrote:
> > MT7530 has a global address age control register, so use it to set
> > ageing time.
> >
> > The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
> >
> > Signed-off-by: DENG Qingfang <dqfext@gmail.com>
> > ---
> > drivers/net/dsa/mt7530.c | 41 ++++++++++++++++++++++++++++++++++++++++
> > drivers/net/dsa/mt7530.h | 13 +++++++++++++
> > 2 files changed, 54 insertions(+)
> >
> > diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> > index 6408402a44f5..99bf8fed6536 100644
> > --- a/drivers/net/dsa/mt7530.c
> > +++ b/drivers/net/dsa/mt7530.c
> > @@ -870,6 +870,46 @@ mt7530_get_sset_count(struct dsa_switch *ds, int port, int sset)
> > return ARRAY_SIZE(mt7530_mib);
> > }
> >
> > +static int
> > +mt7530_set_ageing_time(struct dsa_switch *ds, unsigned int msecs)
> > +{
> > + struct mt7530_priv *priv = ds->priv;
> > + unsigned int secs = msecs / 1000;
> > + unsigned int tmp_age_count;
> > + unsigned int error = -1;
> > + unsigned int age_count;
> > + unsigned int age_unit;
> > +
> > + /* Applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds */
> > + if (secs < 1 || secs > (AGE_CNT_MAX + 1) * (AGE_UNIT_MAX + 1))
> > + return -ERANGE;
> > +
> > + /* iterate through all possible age_count to find the closest pair */
> > + for (tmp_age_count = 0; tmp_age_count <= AGE_CNT_MAX; ++tmp_age_count) {
> > + unsigned int tmp_age_unit = secs / (tmp_age_count + 1) - 1;
> > +
> > + if (tmp_age_unit <= AGE_UNIT_MAX) {
> > + unsigned int tmp_error = secs -
> > + (tmp_age_count + 1) * (tmp_age_unit + 1);
> > +
> > + /* found a closer pair */
> > + if (error > tmp_error) {
> > + error = tmp_error;
> > + age_count = tmp_age_count;
> > + age_unit = tmp_age_unit;
> > + }
>
> I feel that the error calculation is just snake oil. This would be enough:
>
> if (tmp_age_unit <= AGE_UNIT_MAX)
> break;
>
> Explanation:
>
> You are given a number X, and must find A and B such that the error
> E = |(A x B) - X| should be minimum, with
> 1 <= A <= A_max
> 1 <= B <= B_max
>
> It is logical to try with A=1 first. If X / A <= B_max, then of course,
> B = X / 1, and the error E is 0.
>
> If that doesn't work out, and B > B_max, then you go to A=2. That gives
> you another B = X / 2, and the error E is 1. You check again if B <=
> B_max. If it is, that's your answer. B = X / 2, with an error E of 1.
>
> You get my point. Iterating ascendingly through A, and calculating B as
> X / A, already gives you the smallest error as soon as it satisfies the
> B <= B_max requirement.
>
> > +
> > + /* found the exact match, so break the loop */
> > + if (!error)
> > + break;
> > + }
> > + }
> > +
> > + mt7530_write(priv, MT7530_AAC, AGE_CNT(age_count) | AGE_UNIT(age_unit));
> > +
> > + return 0;
> > +}
Thinking more about it, it's not snake oil but is actually correct.
Where I was wrong was the division giving you a certain error, but it
actually only gives a maximum error. Other, larger, divisors can still
give you an error of 0.
If the number you're searching for, X, is, say, a multiple of 3 but not
of 2, and is:
B_max * 1 < X < B_max * 2
then exiting the loop at A=2 would give you an error E=1. But if you
continued the loop, then A=3 would have yielded an error E=0, because X
is a multiple of 3 but not of 2. I should probably go and refresh my
basic arithmetic.
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
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^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
2020-12-08 7:00 ` DENG Qingfang
@ 2020-12-08 22:01 ` Florian Fainelli
-1 siblings, 0 replies; 12+ messages in thread
From: Florian Fainelli @ 2020-12-08 22:01 UTC (permalink / raw)
To: DENG Qingfang, netdev, linux-mediatek, Sean Wang, Landen Chao,
Andrew Lunn, Vivien Didelot, Vladimir Oltean, David S . Miller,
Jakub Kicinski, Matthias Brugger, Russell King
Cc: Frank Wunderlich
On 12/7/20 11:00 PM, DENG Qingfang wrote:
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
--
Florian
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
@ 2020-12-08 22:01 ` Florian Fainelli
0 siblings, 0 replies; 12+ messages in thread
From: Florian Fainelli @ 2020-12-08 22:01 UTC (permalink / raw)
To: DENG Qingfang, netdev, linux-mediatek, Sean Wang, Landen Chao,
Andrew Lunn, Vivien Didelot, Vladimir Oltean, David S . Miller,
Jakub Kicinski, Matthias Brugger, Russell King
Cc: Frank Wunderlich
On 12/7/20 11:00 PM, DENG Qingfang wrote:
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
--
Florian
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^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
2020-12-08 7:00 ` DENG Qingfang
@ 2020-12-09 0:19 ` David Miller
-1 siblings, 0 replies; 12+ messages in thread
From: David Miller @ 2020-12-09 0:19 UTC (permalink / raw)
To: dqfext
Cc: netdev, linux-mediatek, sean.wang, Landen.Chao, andrew,
vivien.didelot, f.fainelli, olteanv, kuba, matthias.bgg, linux,
frank-w
From: DENG Qingfang <dqfext@gmail.com>
Date: Tue, 8 Dec 2020 15:00:28 +0800
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Applied, thanks
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH net-next] net: dsa: mt7530: support setting ageing time
@ 2020-12-09 0:19 ` David Miller
0 siblings, 0 replies; 12+ messages in thread
From: David Miller @ 2020-12-09 0:19 UTC (permalink / raw)
To: dqfext
Cc: andrew, Landen.Chao, f.fainelli, frank-w, netdev, sean.wang,
linux, linux-mediatek, matthias.bgg, kuba, olteanv,
vivien.didelot
From: DENG Qingfang <dqfext@gmail.com>
Date: Tue, 8 Dec 2020 15:00:28 +0800
> MT7530 has a global address age control register, so use it to set
> ageing time.
>
> The applied timer is (AGE_CNT + 1) * (AGE_UNIT + 1) seconds
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Applied, thanks
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^ permalink raw reply [flat|nested] 12+ messages in thread