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>

8 files changed, 26 insertions, 7 deletions

diff --git a/drivers/net/dsa/ocelot/felix.c b/drivers/net/dsa/ocelot/felix.c
index 8492151f8133..cf9317110591 100644
--- a/drivers/net/dsa/ocelot/felix.c
+++ b/drivers/net/dsa/ocelot/felix.c
@@ -422,7 +422,6 @@ static int felix_init_structs(struct felix *felix, int num_phys_ports)
 	ocelot->map		= felix->info->map;
 	ocelot->stats_layout	= felix->info->stats_layout;
 	ocelot->num_stats	= felix->info->num_stats;
-	ocelot->shared_queue_sz	= felix->info->shared_queue_sz;
 	ocelot->num_mact_rows	= felix->info->num_mact_rows;
 	ocelot->vcap		= felix->info->vcap;
 	ocelot->ops		= felix->info->ops;
diff --git a/drivers/net/dsa/ocelot/felix.h b/drivers/net/dsa/ocelot/felix.h
index 4c717324ac2f..5434fe278d2c 100644
--- a/drivers/net/dsa/ocelot/felix.h
+++ b/drivers/net/dsa/ocelot/felix.h
@@ -15,7 +15,6 @@ struct felix_info {
 	const struct reg_field		*regfields;
 	const u32 *const		*map;
 	const struct ocelot_ops		*ops;
-	int				shared_queue_sz;
 	int				num_mact_rows;
 	const struct ocelot_stat_layout	*stats_layout;
 	unsigned int			num_stats;
diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index a87597eef8cf..b68df85e01a1 100644
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1356,7 +1356,6 @@ static const struct felix_info felix_info_vsc9959 = {
 	.stats_layout		= vsc9959_stats_layout,
 	.num_stats		= ARRAY_SIZE(vsc9959_stats_layout),
 	.vcap			= vsc9959_vcap_props,
-	.shared_queue_sz	= 128 * 1024,
 	.num_mact_rows		= 2048,
 	.num_ports		= 6,
 	.num_tx_queues		= FELIX_NUM_TC,
diff --git a/drivers/net/dsa/ocelot/seville_vsc9953.c b/drivers/net/dsa/ocelot/seville_vsc9953.c
index ebbaf6817ec8..b72813da6d9f 100644
--- a/drivers/net/dsa/ocelot/seville_vsc9953.c
+++ b/drivers/net/dsa/ocelot/seville_vsc9953.c
@@ -1181,7 +1181,6 @@ static const struct felix_info seville_info_vsc9953 = {
 	.stats_layout		= vsc9953_stats_layout,
 	.num_stats		= ARRAY_SIZE(vsc9953_stats_layout),
 	.vcap			= vsc9953_vcap_props,
-	.shared_queue_sz	= 256 * 1024,
 	.num_mact_rows		= 2048,
 	.num_ports		= 10,
 	.mdio_bus_alloc		= vsc9953_mdio_bus_alloc,
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;
 
diff --git a/include/soc/mscc/ocelot.h b/include/soc/mscc/ocelot.h
index f3db75c0172b..c17a372335cd 100644
--- a/include/soc/mscc/ocelot.h
+++ b/include/soc/mscc/ocelot.h
@@ -607,7 +607,8 @@ struct ocelot {
 	const struct ocelot_stat_layout	*stats_layout;
 	unsigned int			num_stats;
 
-	int				shared_queue_sz;
+	int				packet_buffer_size;
+	int				num_frame_refs;
 	int				num_mact_rows;
 
 	struct net_device		*hw_bridge_dev;
diff --git a/include/soc/mscc/ocelot_qsys.h b/include/soc/mscc/ocelot_qsys.h
index a814bc2017d8..b7b263a19068 100644
--- a/include/soc/mscc/ocelot_qsys.h
+++ b/include/soc/mscc/ocelot_qsys.h
@@ -77,6 +77,9 @@
 #define QSYS_RES_STAT_MAXUSE(x)                           ((x) & GENMASK(11, 0))
 #define QSYS_RES_STAT_MAXUSE_M                            GENMASK(11, 0)
 
+#define QSYS_MMGT_EQ_CTRL_FP_FREE_CNT(x)                  ((x) & GENMASK(15, 0))
+#define QSYS_MMGT_EQ_CTRL_FP_FREE_CNT_M                   GENMASK(15, 0)
+
 #define QSYS_EVENTS_CORE_EV_FDC(x)                        (((x) << 2) & GENMASK(4, 2))
 #define QSYS_EVENTS_CORE_EV_FDC_M                         GENMASK(4, 2)
 #define QSYS_EVENTS_CORE_EV_FDC_X(x)                      (((x) & GENMASK(4, 2)) >> 2)