net: stmmac: thead: ensure divisor gives proper rate

thead was checking that the stmmac_clk rate was a multiple of the
RGMII rates for 1G and 100M, but didn't check for 10M. Rather than
use this with hard-coded speeds, check that the calculated divisor
gives the required rate by multplying the transmit clock rate back
up to the stmmac clock rate and checking that it agrees.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Drew Fustini <drew@pdp7.com>
Link: https://patch.msgid.link/E1tlToD-004W3g-HB@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
index f16fa341aadb38097a27074469aab2238e6ffc24..f9f2bd65959fa8284599d608fe85ae6f519808a5 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-thead.c
@@ -45,9 +45,6 @@
 #define  TXCLK_DIR_OUTPUT              FIELD_PREP(TXCLK_DIR_MASK, 0)
 #define  TXCLK_DIR_INPUT               FIELD_PREP(TXCLK_DIR_MASK, 1)
 
-#define GMAC_GMII_RGMII_RATE   125000000
-#define GMAC_MII_RATE          25000000
-
 struct thead_dwmac {
        struct plat_stmmacenet_data *plat;
        void __iomem *apb_base;
@@ -124,11 +121,6 @@ static void thead_dwmac_fix_speed(void *priv, int speed, unsigned int mode)
        case PHY_INTERFACE_MODE_RGMII_RXID:
        case PHY_INTERFACE_MODE_RGMII_TXID:
                rate = clk_get_rate(plat->stmmac_clk);
-               if (!rate || rate % GMAC_GMII_RGMII_RATE != 0 ||
-                   rate % GMAC_MII_RATE != 0) {
-                       dev_err(dwmac->dev, "invalid gmac rate %ld\n", rate);
-                       return;
-               }
 
                writel(0, dwmac->apb_base + GMAC_PLLCLK_DIV);
 
@@ -139,6 +131,10 @@ static void thead_dwmac_fix_speed(void *priv, int speed, unsigned int mode)
                }
 
                div = rate / tx_rate;
+               if (rate != tx_rate * div) {
+                       dev_err(dwmac->dev, "invalid gmac rate %lu\n", rate);
+                       return;
+               }
 
                reg = FIELD_PREP(GMAC_PLLCLK_DIV_EN, 1) |
                      FIELD_PREP(GMAC_PLLCLK_DIV_NUM, div);