net: mscc: ocelot: auto-detect packet buffer size and number of frame references

Instead of reading these values from the reference manual and writing
them down into the driver, it appears that the hardware gives us the
option of detecting them dynamically.

The number of frame references corresponds to what the reference manual
notes, however it seems that the frame buffers are reported as slightly
less than the books would indicate. On VSC9959 (Felix), the books say it
should have 128KB of packet buffer, but the registers indicate only
129840 bytes (126.79 KB). Also, the unit of measurement for FREECNT from
the documentation of all these devices is incorrect (taken from an older
generation). This was confirmed by Younes Leroul from Microchip support.

Not having anything better to do with these values at the moment* (this
will change soon), let's just print them.

*The frame buffer size is, in fact, used to calculate the tail dropping
watermarks.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 21 insertions, 2 deletions

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index af620f7ce469..3af8e607c8a9 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -1354,7 +1354,7 @@ void ocelot_port_set_maxlen(struct ocelot *ocelot, int port, size_t sdu)
 			    pause_stop);
 
 	/* Tail dropping watermarks */
-	atop_tot = (ocelot->shared_queue_sz - 9 * maxlen) /
+	atop_tot = (ocelot->packet_buffer_size - 9 * maxlen) /
 		   OCELOT_BUFFER_CELL_SZ;
 	atop = (9 * maxlen) / OCELOT_BUFFER_CELL_SZ;
 	ocelot_write_rix(ocelot, ocelot->ops->wm_enc(atop), SYS_ATOP, port);
@@ -1467,6 +1467,25 @@ static void ocelot_cpu_port_init(struct ocelot *ocelot)
 			 ANA_PORT_VLAN_CFG, cpu);
 }
 
+static void ocelot_detect_features(struct ocelot *ocelot)
+{
+	int mmgt, eq_ctrl;
+
+	/* For Ocelot, Felix, Seville, Serval etc, SYS:MMGT:MMGT:FREECNT holds
+	 * the number of 240-byte free memory words (aka 4-cell chunks) and not
+	 * 192 bytes as the documentation incorrectly says.
+	 */
+	mmgt = ocelot_read(ocelot, SYS_MMGT);
+	ocelot->packet_buffer_size = 240 * SYS_MMGT_FREECNT(mmgt);
+
+	eq_ctrl = ocelot_read(ocelot, QSYS_EQ_CTRL);
+	ocelot->num_frame_refs = QSYS_MMGT_EQ_CTRL_FP_FREE_CNT(eq_ctrl);
+
+	dev_info(ocelot->dev,
+		 "Detected %d bytes of packet buffer and %d frame references\n",
+		 ocelot->packet_buffer_size, ocelot->num_frame_refs);
+}
+
 int ocelot_init(struct ocelot *ocelot)
 {
 	char queue_name[32];
@@ -1509,6 +1528,7 @@ int ocelot_init(struct ocelot *ocelot)
 
 	INIT_LIST_HEAD(&ocelot->multicast);
 	INIT_LIST_HEAD(&ocelot->pgids);
+	ocelot_detect_features(ocelot);
 	ocelot_mact_init(ocelot);
 	ocelot_vlan_init(ocelot);
 	ocelot_vcap_init(ocelot);
diff --git a/drivers/net/ethernet/mscc/ocelot_vsc7514.c b/drivers/net/ethernet/mscc/ocelot_vsc7514.c
index 9cf2bc5f4289..7135ad18affe 100644
--- a/drivers/net/ethernet/mscc/ocelot_vsc7514.c
+++ b/drivers/net/ethernet/mscc/ocelot_vsc7514.c
@@ -517,7 +517,6 @@ static int ocelot_chip_init(struct ocelot *ocelot, const struct ocelot_ops *ops)
 	ocelot->map = ocelot_regmap;
 	ocelot->stats_layout = ocelot_stats_layout;
 	ocelot->num_stats = ARRAY_SIZE(ocelot_stats_layout);
-	ocelot->shared_queue_sz = 224 * 1024;
 	ocelot->num_mact_rows = 1024;
 	ocelot->ops = ops;