From: Jesper Nilsson jesper.nilsson@axis.com
[ 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@axis.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index dbd56fefa2f3..0a7ff854d1c3 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -178,7 +178,7 @@ 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; } }