diff options
| author | Maxime Chevallier <maxime.chevallier@bootlin.com> | 2026-08-02 13:40:13 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-08-03 18:35:45 -0700 |
| commit | b6a89c8ef34f84488f877e29b14f0c843bfdff51 (patch) | |
| tree | ceccbcad15b116294d38f1adad9a75d7df9e02fb | |
| parent | c98610c2eb7002436f6fca55b21c63200644549a (diff) | |
net: stmmac: ethtool: Comment the magic numbers in RIWT computation
Receive Interrupt Watchdog Timer is an RX interrupt coalescing mechanism
used by some variants of dwmac. It allows waiting a bit before
triggering the rx interrupts, allowing for batch processing.
The RIWT is configured with a granularity of 256 stmmac clk ticks. Let's
add a comment for that and wrap the raw "1000000" into USEC_PER_SEC, as
we're computing "how many clock cycles in one microsec" with that step.
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20260802114015.214212-2-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c index 92585d27ab88..eebfd6976aaa 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c @@ -759,7 +759,10 @@ static u32 stmmac_usec2riwt(u32 usec, struct stmmac_priv *priv) return 0; } - return (usec * (clk / 1000000)) / 256; + /* Receive Interrupt Watchdog Timer (riwt) has a resolution of 256 + * ticks. + */ + return (usec * (clk / USEC_PER_SEC)) / 256; } static u32 stmmac_riwt2usec(u32 riwt, struct stmmac_priv *priv) @@ -772,7 +775,7 @@ static u32 stmmac_riwt2usec(u32 riwt, struct stmmac_priv *priv) return 0; } - return (riwt * 256) / (clk / 1000000); + return (riwt * 256) / (clk / USEC_PER_SEC); } static int __stmmac_get_coalesce(struct net_device *dev, |