net: dsa: microchip: add support for credit based shaper

KSZ9477, KSZ9567, KSZ9563, KSZ8563 and LAN937x supports Credit based
shaper. To differentiate the chip supporting cbs, tc_cbs_supported
flag is introduced in ksz_chip_data.
And KSZ series has 16bit Credit increment registers whereas LAN937x has
24bit register. The value to be programmed in the credit increment is
determined using the successive multiplication method to convert decimal
fraction to hexadecimal fraction.
For example: if idleslope is 10000 and sendslope is -90000, then
bandwidth is 10000 - (-90000) = 100000.
The 10% bandwidth of 100Mbps means 10/100 = 0.1(decimal). This value has
to be converted to hexa.
1) 0.1 * 16 = 1.6  --> fraction 0.6 Carry = 1 (MSB)
2) 0.6 * 16 = 9.6  --> fraction 0.6 Carry = 9
3) 0.6 * 16 = 9.6  --> fraction 0.6 Carry = 9
4) 0.6 * 16 = 9.6  --> fraction 0.6 Carry = 9
5) 0.6 * 16 = 9.6  --> fraction 0.6 Carry = 9
6) 0.6 * 16 = 9.6  --> fraction 0.6 Carry = 9 (LSB)
Now 0.1(decimal) becomes 0.199999(Hex).
If it is LAN937x, 24 bit value will be programmed to Credit Inc
register, 0x199999. For others 16 bit value will be prgrammed, 0x1999.

Signed-off-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/net/dsa/microchip/ksz9477.h b/drivers/net/dsa/microchip/ksz9477.h
index 2554cb63d326..b6f7e3c46e3f 100644
--- a/drivers/net/dsa/microchip/ksz9477.h
+++ b/drivers/net/dsa/microchip/ksz9477.h
@@ -51,6 +51,7 @@ int ksz9477_mdb_del(struct ksz_device *dev, int port,
 		    const struct switchdev_obj_port_mdb *mdb, struct dsa_db db);
 int ksz9477_change_mtu(struct ksz_device *dev, int port, int mtu);
 void ksz9477_config_cpu_port(struct dsa_switch *ds);
+int ksz9477_tc_cbs_set_cinc(struct ksz_device *dev, int port, u32 val);
 int ksz9477_enable_stp_addr(struct ksz_device *dev);
 int ksz9477_reset_switch(struct ksz_device *dev);
 int ksz9477_dsa_init(struct ksz_device *dev);