[lkml]   [2018]   [May]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH net-next] net: phy: sfp: handle cases where neither BR,min nor BR,max is given
Hi Russell,

On Tue, May 08, 2018 at 01:30:26PM +0100, Russell King - ARM Linux wrote:
> The electronic engineer in me says that using zero isn't really valid
> because there are coupling capacitors in the SFP module that block DC.
> These blocking capacitors are required by the SFP+ specs to have a high
> pass pole of between 20kHz and 100kHz - in other words, frequencies
> below this are attenuated by the coupling capacitors. The relationship
> between this and the bit rate will be a function of the encoding, so we
> can't come to a definitive figure without some math (and I want to be
> lazy about that!)
> Practically, we're talking about SerDes Ethernet, where the bit rate is
> no lower than 100Mbps [*], which will always have a frequency well above
> this cut-off. So, I don't have any problem with your approach to
> setting the minimum to zero. Therefore,
> Acked-by: Russell King <>

Thanks for looking into it!

Antoine Ténart, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering

 \ /
  Last update: 2018-05-14 10:17    [W:0.063 / U:1.412 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site