add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/drivers/thunderbolt/usb4.c
..
..
@@ -1636,18 +1636,30 @@
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 						    int downstream_bw)
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 {
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 	u32 val, ubw, dbw, scale;
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-	int ret;
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+	int ret, max_bw;
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-	/* Read the used scale, hardware default is 0 */
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-	ret = tb_port_read(port, &scale, TB_CFG_PORT,
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-			   port->cap_adap + ADP_USB3_CS_3, 1);
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+	/* Figure out suitable scale */
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+	scale = 0;
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+	max_bw = max(upstream_bw, downstream_bw);
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+	while (scale < 64) {
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+		if (mbps_to_usb3_bw(max_bw, scale) < 4096)
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+			break;
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+		scale++;
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+	}
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+
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+	if (WARN_ON(scale >= 64))
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+		return -EINVAL;
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+
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+	ret = tb_port_write(port, &scale, TB_CFG_PORT,
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+			    port->cap_adap + ADP_USB3_CS_3, 1);
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 	if (ret)
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 		return ret;
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-	scale &= ADP_USB3_CS_3_SCALE_MASK;
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 	ubw = mbps_to_usb3_bw(upstream_bw, scale);
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 	dbw = mbps_to_usb3_bw(downstream_bw, scale);
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+	tb_port_dbg(port, "scaled bandwidth %u/%u, scale %u\n", ubw, dbw, scale);
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+
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 	ret = tb_port_read(port, &val, TB_CFG_PORT,
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 			   port->cap_adap + ADP_USB3_CS_2, 1);
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 	if (ret)