From 5a17818682cf43ad0fdd6035945f3b7a8c9dc5e9 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Thu, 6 Apr 2023 14:42:46 +0300 Subject: net: dsa: replace NETDEV_PRE_CHANGE_HWTSTAMP notifier with a stub There was a sort of rush surrounding commit 88c0a6b503b7 ("net: create a netdev notifier for DSA to reject PTP on DSA master"), due to a desire to convert DSA's attempt to deny TX timestamping on a DSA master to something that doesn't block the kernel-wide API conversion from ndo_eth_ioctl() to ndo_hwtstamp_set(). What was required was a mechanism that did not depend on ndo_eth_ioctl(), and what was provided was a mechanism that did not depend on ndo_eth_ioctl(), while at the same time introducing something that wasn't absolutely necessary - a new netdev notifier. There have been objections from Jakub Kicinski that using notifiers in general when they are not absolutely necessary creates complications to the control flow and difficulties to maintainers who look at the code. So there is a desire to not use notifiers. In addition to that, the notifier chain gets called even if there is no DSA in the system and no one is interested in applying any restriction. Take the model of udp_tunnel_nic_ops and introduce a stub mechanism, through which net/core/dev_ioctl.c can call into DSA even when CONFIG_NET_DSA=m. Compared to the code that existed prior to the notifier conversion, aka what was added in commits: - 4cfab3566710 ("net: dsa: Add wrappers for overloaded ndo_ops") - 3369afba1e46 ("net: Call into DSA netdevice_ops wrappers") this is different because we are not overloading any struct net_device_ops of the DSA master anymore, but rather, we are exposing a rather specific functionality which is orthogonal to which API is used to enable it - ndo_eth_ioctl() or ndo_hwtstamp_set(). Also, what is similar is that both approaches use function pointers to get from built-in code to DSA. There is no point in replicating the function pointers towards __dsa_master_hwtstamp_validate() once for every CPU port (dev->dsa_ptr). Instead, it is sufficient to introduce a singleton struct dsa_stubs, built into the kernel, which contains a single function pointer to __dsa_master_hwtstamp_validate(). I find this approach preferable to what we had originally, because dev->dsa_ptr->netdev_ops->ndo_do_ioctl() used to require going through struct dsa_port (dev->dsa_ptr), and so, this was incompatible with any attempts to add any data encapsulation and hide DSA data structures from the outside world. Link: https://lore.kernel.org/netdev/20230403083019.120b72fd@kernel.org/ Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller --- net/dsa/dsa.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'net/dsa/dsa.c') diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c index e5f156940c67..ab1afe67fd18 100644 --- a/net/dsa/dsa.c +++ b/net/dsa/dsa.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include "devlink.h" @@ -1702,6 +1703,20 @@ bool dsa_mdb_present_in_other_db(struct dsa_switch *ds, int port, } EXPORT_SYMBOL_GPL(dsa_mdb_present_in_other_db); +static const struct dsa_stubs __dsa_stubs = { + .master_hwtstamp_validate = __dsa_master_hwtstamp_validate, +}; + +static void dsa_register_stubs(void) +{ + dsa_stubs = &__dsa_stubs; +} + +static void dsa_unregister_stubs(void) +{ + dsa_stubs = NULL; +} + static int __init dsa_init_module(void) { int rc; @@ -1721,6 +1736,8 @@ static int __init dsa_init_module(void) if (rc) goto netlink_register_fail; + dsa_register_stubs(); + return 0; netlink_register_fail: @@ -1735,6 +1752,8 @@ module_init(dsa_init_module); static void __exit dsa_cleanup_module(void) { + dsa_unregister_stubs(); + rtnl_link_unregister(&dsa_link_ops); dsa_slave_unregister_notifier(); -- cgit From b79d7c14f48083abb3fb061370c0c64a569edf4c Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Sat, 17 Jun 2023 09:26:48 +0300 Subject: net: dsa: introduce preferred_default_local_cpu_port and use on MT7530 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Since the introduction of the OF bindings, DSA has always had a policy that in case multiple CPU ports are present in the device tree, the numerically smallest one is always chosen. The MT7530 switch family, except the switch on the MT7988 SoC, has 2 CPU ports, 5 and 6, where port 6 is preferable on the MT7531BE switch because it has higher bandwidth. The MT7530 driver developers had 3 options: - to modify DSA when the MT7531 switch support was introduced, such as to prefer the better port - to declare both CPU ports in device trees as CPU ports, and live with the sub-optimal performance resulting from not preferring the better port - to declare just port 6 in the device tree as a CPU port Of course they chose the path of least resistance (3rd option), kicking the can down the road. The hardware description in the device tree is supposed to be stable - developers are not supposed to adopt the strategy of piecemeal hardware description, where the device tree is updated in lockstep with the features that the kernel currently supports. Now, as a result of the fact that they did that, any attempts to modify the device tree and describe both CPU ports as CPU ports would make DSA change its default selection from port 6 to 5, effectively resulting in a performance degradation visible to users with the MT7531BE switch as can be seen below. Without preferring port 6: [ ID][Role] Interval Transfer Bitrate Retr [ 5][TX-C] 0.00-20.00 sec 374 MBytes 157 Mbits/sec 734 sender [ 5][TX-C] 0.00-20.00 sec 373 MBytes 156 Mbits/sec receiver [ 7][RX-C] 0.00-20.00 sec 1.81 GBytes 778 Mbits/sec 0 sender [ 7][RX-C] 0.00-20.00 sec 1.81 GBytes 777 Mbits/sec receiver With preferring port 6: [ ID][Role] Interval Transfer Bitrate Retr [ 5][TX-C] 0.00-20.00 sec 1.99 GBytes 856 Mbits/sec 273 sender [ 5][TX-C] 0.00-20.00 sec 1.99 GBytes 855 Mbits/sec receiver [ 7][RX-C] 0.00-20.00 sec 1.72 GBytes 737 Mbits/sec 15 sender [ 7][RX-C] 0.00-20.00 sec 1.71 GBytes 736 Mbits/sec receiver Using one port for WAN and the other ports for LAN is a very popular use case which is what this test emulates. As such, this change proposes that we retroactively modify stable kernels (which don't support the modification of the CPU port assignments, so as to let user space fix the problem and restore the throughput) to keep the mt7530 driver preferring port 6 even with device trees where the hardware is more fully described. Fixes: c288575f7810 ("net: dsa: mt7530: Add the support of MT7531 switch") Signed-off-by: Vladimir Oltean Signed-off-by: Arınç ÜNAL Reviewed-by: Russell King (Oracle) Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller --- net/dsa/dsa.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) (limited to 'net/dsa/dsa.c') diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c index ab1afe67fd18..1afed89e03c0 100644 --- a/net/dsa/dsa.c +++ b/net/dsa/dsa.c @@ -403,6 +403,24 @@ static int dsa_tree_setup_default_cpu(struct dsa_switch_tree *dst) return 0; } +static struct dsa_port * +dsa_switch_preferred_default_local_cpu_port(struct dsa_switch *ds) +{ + struct dsa_port *cpu_dp; + + if (!ds->ops->preferred_default_local_cpu_port) + return NULL; + + cpu_dp = ds->ops->preferred_default_local_cpu_port(ds); + if (!cpu_dp) + return NULL; + + if (WARN_ON(!dsa_port_is_cpu(cpu_dp) || cpu_dp->ds != ds)) + return NULL; + + return cpu_dp; +} + /* Perform initial assignment of CPU ports to user ports and DSA links in the * fabric, giving preference to CPU ports local to each switch. Default to * using the first CPU port in the switch tree if the port does not have a CPU @@ -410,12 +428,16 @@ static int dsa_tree_setup_default_cpu(struct dsa_switch_tree *dst) */ static int dsa_tree_setup_cpu_ports(struct dsa_switch_tree *dst) { - struct dsa_port *cpu_dp, *dp; + struct dsa_port *preferred_cpu_dp, *cpu_dp, *dp; list_for_each_entry(cpu_dp, &dst->ports, list) { if (!dsa_port_is_cpu(cpu_dp)) continue; + preferred_cpu_dp = dsa_switch_preferred_default_local_cpu_port(cpu_dp->ds); + if (preferred_cpu_dp && preferred_cpu_dp != cpu_dp) + continue; + /* Prefer a local CPU port */ dsa_switch_for_each_port(dp, cpu_dp->ds) { /* Prefer the first local CPU port found */ -- cgit