This is a note to let you know that I've just added the patch titled
net: stmmac: allow CSR clock of 300MHz
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-stmmac-allow-csr-clock-of-300mhz.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 60af33f4902a75b36091cc53bcf8ca943e6f534d
Author: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
Date: Fri Sep 10 21:55:34 2021 +0200
net: stmmac: allow CSR clock of 300MHz
[ Upstream commit 08dad2f4d541fcfe5e7bfda72cc6314bbfd2802f ]
The Synopsys Ethernet IP uses the CSR clock as a base clock for MDC.
The divisor used is set in the MAC_MDIO_Address register field CR
(Clock Rate)
The divisor is there to change the CSR clock into a clock that falls
below the IEEE 802.3 specified max frequency of 2.5MHz.
If the CSR clock is 300MHz, the code falls back to using the reset
value in the MAC_MDIO_Address register, as described in the comment
above this code.
However, 300MHz is actually an allowed value and the proper divider
can be estimated quite easily (it's just 1Hz difference!)
A CSR frequency of 300MHz with the maximum clock rate value of 0x5
(STMMAC_CSR_250_300M, a divisor of 124) gives somewhere around
~2.42MHz which is below the IEEE 802.3 specified maximum.
For the ARTPEC-8 SoC, the CSR clock is this problematic 300MHz,
and unfortunately, the reset-value of the MAC_MDIO_Address CR field
is 0x0.
This leads to a clock rate of zero and a divisor of 42, and gives an
MDC frequency of ~7.14MHz.
Allow CSR clock of 300MHz by making the comparison inclusive.
Signed-off-by: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 4e7cfd3bfcd2..e09851c7da9b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -225,7 +225,7 @@ static void stmmac_clk_csr_set(struct stmmac_priv *priv)
priv->clk_csr = STMMAC_CSR_100_150M;
else if ((clk_rate >= CSR_F_150M) && (clk_rate < CSR_F_250M))
priv->clk_csr = STMMAC_CSR_150_250M;
- else if ((clk_rate >= CSR_F_250M) && (clk_rate < CSR_F_300M))
+ else if ((clk_rate >= CSR_F_250M) && (clk_rate <= CSR_F_300M))
priv->clk_csr = STMMAC_CSR_250_300M;
}
