Re: [PATCH v3 net-next 20/24] net: dsa: sja1105: Error out if RGMII delays are requested in DT
From: Vladimir Oltean
Date: Sat Apr 13 2019 - 17:31:18 EST
On Sat, 13 Apr 2019 at 23:47, Jiri Pirko <jiri@xxxxxxxxxxx> wrote:
>
> Sat, Apr 13, 2019 at 03:28:18AM CEST, olteanv@xxxxxxxxx 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@xxxxxxxxx>
> >Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> >---
> >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?
Thanks,
-Vladimir
>
> > .reset_cmd = sja1105pqrs_reset_cmd,
> > .name = "SJA1105S",
> > };
> >--
> >2.17.1
> >