Re: [PATCH v3 net-next 20/24] net: dsa: sja1105: Error out if RGMII delays are requested in DT

[Jiri Pirko <jiri@resnulli.us>]

Sat, Apr 13, 2019 at 11:31:01PM CEST, olteanv@gmail.com wrote:
>On Sat, 13 Apr 2019 at 23:47, Jiri Pirko <jiri@resnulli.us> wrote:
>>
>> Sat, Apr 13, 2019 at 03:28:18AM CEST, olteanv@gmail.com wrote:
>> >Documentation/devicetree/bindings/net/ethernet.txt is confusing because
>> >it says what the MAC should not do, but not what it *should* do:
>> >
>> >  * "rgmii-rxid" (RGMII with internal RX delay provided by the PHY, the MAC
>> >     should not add an RX delay in this case)
>> >
>> >The gap in semantics is threefold:
>> >1. Is it illegal for the MAC to apply the Rx internal delay by itself,
>> >   and simplify the phy_mode (mask off "rgmii-rxid" into "rgmii") before
>> >   passing it to of_phy_connect? The documentation would suggest yes.
>> >1. For "rgmii-rxid", while the situation with the Rx clock skew is more
>> >   or less clear (needs to be added by the PHY), what should the MAC
>> >   driver do about the Tx delays? Is it an implicit wild card for the
>> >   MAC to apply delays in the Tx direction if it can? What if those were
>> >   already added as serpentine PCB traces, how could that be made more
>> >   obvious through DT bindings so that the MAC doesn't attempt to add
>> >   them twice and again potentially break the link?
>> >3. If the interface is a fixed-link and therefore the PHY object is
>> >   fixed (a purely software entity that obviously cannot add clock
>> >   skew), what is the meaning of the above property?
>> >
>> >So an interpretation of the RGMII bindings was chosen that hopefully
>> >does not contradict their intention but also makes them more applied.
>> >The SJA1105 driver understands to act upon "rgmii-*id" phy-mode bindings
>> >if the port is in the PHY role (either explicitly, or if it is a
>> >fixed-link). Otherwise it always passes the duty of setting up delays to
>> >the PHY driver.
>> >
>> >The error behavior that this patch adds is required on SJA1105E/T where
>> >the MAC really cannot apply internal delays. If the other end of the
>> >fixed-link cannot apply RGMII delays either (this would be specified
>> >through its own DT bindings), then the situation requires PCB delays.
>> >
>> >For SJA1105P/Q/R/S, this is however hardware supported and the error is
>> >thus only temporary. I created a stub function pointer for configuring
>> >delays per-port on RXC and TXC, and will implement it when I have access
>> >to a board with this hardware setup.
>> >
>> >Meanwhile do not allow the user to select an invalid configuration.
>> >
>> >Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
>> >Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
>> >---
>> >Changes in v3:
>> >None.
>> >
>> >Changes in v2:
>> >Patch is new.
>> >
>> > drivers/net/dsa/sja1105/sja1105.h          |  3 ++
>> > drivers/net/dsa/sja1105/sja1105_clocking.c |  7 ++++-
>> > drivers/net/dsa/sja1105/sja1105_main.c     | 32 +++++++++++++++++++++-
>> > drivers/net/dsa/sja1105/sja1105_spi.c      |  6 ++++
>> > 4 files changed, 46 insertions(+), 2 deletions(-)
>> >
>> >diff --git a/drivers/net/dsa/sja1105/sja1105.h b/drivers/net/dsa/sja1105/sja1105.h
>> >index b7e745c0bb3a..3c16b991032c 100644
>> >--- a/drivers/net/dsa/sja1105/sja1105.h
>> >+++ b/drivers/net/dsa/sja1105/sja1105.h
>> >@@ -22,6 +22,8 @@
>> >
>> > struct sja1105_port {
>> >       struct dsa_port *dp;
>> >+      bool rgmii_rx_delay;
>> >+      bool rgmii_tx_delay;
>> >       struct work_struct xmit_work;
>> >       struct sja1105_skb_ring xmit_ring;
>> > };
>> >@@ -61,6 +63,7 @@ struct sja1105_info {
>> >       const struct sja1105_table_ops *static_ops;
>> >       const struct sja1105_regs *regs;
>> >       int (*reset_cmd)(const void *ctx, const void *data);
>> >+      int (*setup_rgmii_delay)(const void *ctx, int port, bool rx, bool tx);
>> >       const char *name;
>> > };
>> >
>> >diff --git a/drivers/net/dsa/sja1105/sja1105_clocking.c b/drivers/net/dsa/sja1105/sja1105_clocking.c
>> >index d40da3d52464..c02fec181676 100644
>> >--- a/drivers/net/dsa/sja1105/sja1105_clocking.c
>> >+++ b/drivers/net/dsa/sja1105/sja1105_clocking.c
>> >@@ -432,7 +432,12 @@ static int rgmii_clocking_setup(struct sja1105_private *priv, int port)
>> >               dev_err(dev, "Failed to configure Tx pad registers\n");
>> >               return rc;
>> >       }
>> >-      return 0;
>> >+      if (!priv->info->setup_rgmii_delay)
>> >+              return 0;
>> >+
>> >+      return priv->info->setup_rgmii_delay(priv, port,
>> >+                                           priv->ports[port].rgmii_rx_delay,
>> >+                                           priv->ports[port].rgmii_tx_delay);
>> > }
>> >
>> > static int sja1105_cgu_rmii_ref_clk_config(struct sja1105_private *priv,
>> >diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
>> >index e4abf8fb2013..5f7ddb1da006 100644
>> >--- a/drivers/net/dsa/sja1105/sja1105_main.c
>> >+++ b/drivers/net/dsa/sja1105/sja1105_main.c
>> >@@ -555,6 +555,21 @@ static int sja1105_static_config_load(struct sja1105_private *priv,
>> >       return sja1105_static_config_upload(priv);
>> > }
>> >
>> >+static void sja1105_parse_rgmii_delay(const struct sja1105_dt_port *in,
>> >+                                    struct sja1105_port *out)
>> >+{
>> >+      if (in->role == XMII_MAC)
>> >+              return;
>> >+
>> >+      if (in->phy_mode == PHY_INTERFACE_MODE_RGMII_RXID ||
>> >+          in->phy_mode == PHY_INTERFACE_MODE_RGMII_ID)
>> >+              out->rgmii_rx_delay = true;
>> >+
>> >+      if (in->phy_mode == PHY_INTERFACE_MODE_RGMII_TXID ||
>> >+          in->phy_mode == PHY_INTERFACE_MODE_RGMII_ID)
>> >+              out->rgmii_tx_delay = true;
>> >+}
>> >+
>> > static int sja1105_parse_ports_node(struct sja1105_private *priv,
>> >                                   struct sja1105_dt_port *ports,
>> >                                   struct device_node *ports_node)
>> >@@ -1315,13 +1330,28 @@ static int sja1105_setup(struct dsa_switch *ds)
>> > {
>> >       struct sja1105_dt_port ports[SJA1105_NUM_PORTS];
>> >       struct sja1105_private *priv = ds->priv;
>> >-      int rc;
>> >+      int rc, i;
>> >
>> >       rc = sja1105_parse_dt(priv, ports);
>> >       if (rc < 0) {
>> >               dev_err(ds->dev, "Failed to parse DT: %d\n", rc);
>> >               return rc;
>> >       }
>> >+
>> >+      /* Error out early if internal delays are required through DT
>> >+       * and we can't apply them.
>> >+       */
>> >+      for (i = 0; i < SJA1105_NUM_PORTS; i++) {
>> >+              sja1105_parse_rgmii_delay(&ports[i], &priv->ports[i]);
>> >+
>> >+              if ((priv->ports[i].rgmii_rx_delay ||
>> >+                   priv->ports[i].rgmii_tx_delay) &&
>> >+                   !priv->info->setup_rgmii_delay) {
>> >+                      dev_err(ds->dev, "RGMII delay not supported\n");
>> >+                      return -EINVAL;
>> >+              }
>> >+      }
>> >+
>> >       /* Create and send configuration down to device */
>> >       rc = sja1105_static_config_load(priv, ports);
>> >       if (rc < 0) {
>> >diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c
>> >index 09cb28e9be20..e4ef4d8048b2 100644
>> >--- a/drivers/net/dsa/sja1105/sja1105_spi.c
>> >+++ b/drivers/net/dsa/sja1105/sja1105_spi.c
>> >@@ -499,6 +499,7 @@ struct sja1105_info sja1105e_info = {
>> >       .part_no                = SJA1105ET_PART_NO,
>> >       .static_ops             = sja1105e_table_ops,
>> >       .dyn_ops                = sja1105et_dyn_ops,
>> >+      .setup_rgmii_delay      = NULL,
>> >       .reset_cmd              = sja1105et_reset_cmd,
>> >       .regs                   = &sja1105et_regs,
>> >       .name                   = "SJA1105E",
>> >@@ -508,6 +509,7 @@ struct sja1105_info sja1105t_info = {
>> >       .part_no                = SJA1105ET_PART_NO,
>> >       .static_ops             = sja1105t_table_ops,
>> >       .dyn_ops                = sja1105et_dyn_ops,
>> >+      .setup_rgmii_delay      = NULL,
>> >       .reset_cmd              = sja1105et_reset_cmd,
>> >       .regs                   = &sja1105et_regs,
>> >       .name                   = "SJA1105T",
>> >@@ -517,6 +519,7 @@ struct sja1105_info sja1105p_info = {
>> >       .part_no                = SJA1105P_PART_NO,
>> >       .static_ops             = sja1105p_table_ops,
>> >       .dyn_ops                = sja1105pqrs_dyn_ops,
>> >+      .setup_rgmii_delay      = NULL,
>> >       .reset_cmd              = sja1105pqrs_reset_cmd,
>> >       .regs                   = &sja1105pqrs_regs,
>> >       .name                   = "SJA1105P",
>> >@@ -526,6 +529,7 @@ struct sja1105_info sja1105q_info = {
>> >       .part_no                = SJA1105Q_PART_NO,
>> >       .static_ops             = sja1105q_table_ops,
>> >       .dyn_ops                = sja1105pqrs_dyn_ops,
>> >+      .setup_rgmii_delay      = NULL,
>> >       .reset_cmd              = sja1105pqrs_reset_cmd,
>> >       .regs                   = &sja1105pqrs_regs,
>> >       .name                   = "SJA1105Q",
>> >@@ -535,6 +539,7 @@ struct sja1105_info sja1105r_info = {
>> >       .part_no                = SJA1105R_PART_NO,
>> >       .static_ops             = sja1105r_table_ops,
>> >       .dyn_ops                = sja1105pqrs_dyn_ops,
>> >+      .setup_rgmii_delay      = NULL,
>> >       .reset_cmd              = sja1105pqrs_reset_cmd,
>> >       .regs                   = &sja1105pqrs_regs,
>> >       .name                   = "SJA1105R",
>> >@@ -545,6 +550,7 @@ struct sja1105_info sja1105s_info = {
>> >       .static_ops             = sja1105s_table_ops,
>> >       .dyn_ops                = sja1105pqrs_dyn_ops,
>> >       .regs                   = &sja1105pqrs_regs,
>> >+      .setup_rgmii_delay      = NULL,
>>
>> You don't need to set this to NULL. Please avoid that.
>>
>
>Hi Jiri, why not?

If you don't assign, it is already NULL. so the assignment to NULL is
pointless.


>
>Thanks,
>-Vladimir
>
>>
>> >       .reset_cmd              = sja1105pqrs_reset_cmd,
>> >       .name                   = "SJA1105S",
>> > };
>> >--
>> >2.17.1
>> >