ice: default to TIME_REF instead of TXCO on E825-C

JIRA: https://issues.redhat.com/browse/RHEL-104246

Upstream commit(s):
commit 8b49875
Author: Jacob Keller <jacob.e.keller@intel.com>
Date:   Mon Jun 23 17:30:04 2025 -0700

    ice: default to TIME_REF instead of TXCO on E825-C

    The driver currently defaults to the internal oscillator as the clock
    source for E825-C hardware. While this clock source is labeled TCXO,
    indicating a temperature compensated oscillator, this is only true for some
    board designs. Many board designs have a less capable oscillator. The
    E825-C hardware may also have its clock source set to the TIME_REF pin.
    This pin is connected to the DPLL and is often a more stable clock source.
    The choice of the internal oscillator is not suitable for all systems,
    especially those which want to enable SyncE support.

    There is currently no interface available for users to configure the clock
    source. Other variants of the E82x board have the clock source configured
    in the NVM, but E825-C lacks this capability, so different board designs
    cannot select a different default clock via firmware.

    In most setups, the TIME_REF is a suitable default clock source.
    Additionally, we now fall back to the internal oscillator automatically if
    the TIME_REF clock source cannot be locked.

    Change the default clock source for E825-C to TIME_REF. Note that the
    driver logs a dev_dbg message upon configuring the TSPLL which includes the
    clock source and frequency. This can be enabled to confirm which clock
    source is in use.

    Longterm a proper interface to dynamically introspect and change the clock
    source will be designed (perhaps some extension of the DPLL subsystem?)

    Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
    Tested-by: Rinitha S <sx.rinitha@intel.com>
    Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Signed-off-by: Petr Oros <poros@redhat.com>

Author: orosp

drivers/net/ethernet/intel/ice/ice_common.c

@@ -2302,7 +2302,7 @@ ice_parse_1588_func_caps(struct ice_hw *hw, struct ice_hw_func_caps *func_p,
 		info->clk_src = ((number & ICE_TS_CLK_SRC_M) != 0);
 	} else {
 		info->clk_freq = ICE_TSPLL_FREQ_156_250;
-		info->clk_src = ICE_CLK_SRC_TCXO;
+		info->clk_src = ICE_CLK_SRC_TIME_REF;
 	}
 
 	if (info->clk_freq < NUM_ICE_TSPLL_FREQ) {