netdev - Re: [Intel-wired-lan] [PATCH v3 15/15] ice: change default clock source for E825-C

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Message-ID: <6b4ddead-ab12-4dea-9b02-1943d6330c01@molgen.mpg.de>
Date: Thu, 1 May 2025 07:49:05 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Jacob Keller <jacob.e.keller@...el.com>
Cc: Anthony Nguyen <anthony.l.nguyen@...el.com>, netdev@...r.kernel.org,
 intel-wired-lan@...ts.osuosl.org,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Aleksandr Loktionov <aleksandr.loktionov@...el.com>,
 Milena Olech <milena.olech@...el.com>,
 Michal Kubiak <michal.kubiak@...el.com>,
 Karol Kolacinski <karol.kolacinski@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH v3 15/15] ice: change default clock
 source for E825-C

Dear Jacob,


Thank you for the patch. For the summary, I suggest the more specific:

ice: Default to clock source TIME_REF for E825-C over TCXO

or

ice: E825-C: Default to clock source TIME_REF over TCXO

Am 01.05.25 um 00:51 schrieb Jacob Keller:
> 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. Longer term, a
> proper interface (perhaps through dpll subsystem?) to introspect and
> configure the clock source should be designed.
> 
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
> ---
>   drivers/net/ethernet/intel/ice/ice_common.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
> index e5099a3ccb854424f98c5fb1524f49bde1ca4534..bfa3f58c1104def9954073501012bb58a13e8821 100644
> --- a/drivers/net/ethernet/intel/ice/ice_common.c
> +++ b/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) {

As there are now Linux kernels configured with different clock sources, 
and there is apparently no way to introspect it from a running system, 
does it make sense to log it?


Kind regards,

Paul