Hi Rob, On 2016/11/16 6:26, Rob Herring wrote: > On Mon, Nov 14, 2016 at 12:11:06PM +0800, Shawn Lin wrote: >> Rockchip's RC outputs 100MHz reference clock but there are >> two methods for PHY to generate it. >> >> (1)One of them is to use system PLL to generate 100MHz clock and >> the PHY will relock it and filter signal noise then outputs the >> reference clock. >> >> (2)Another way is to share Soc's 24MHZ crystal oscillator with >> PHY and force PHY's DLL to generate 100MHz internally. >> >> When using case(2), the exit from L0s doesn't work fine occasionally >> due to the broken design of RC receiver's logical circuit. So even if >> we use extended-synch, it still fails for PHY to relock the bits from >> FTS sometimes. This will hang the system. >> >> Maybe we could argue that why not use case(1) to avoid it? The reason >> is that as we could see the reference clock is derived from system PLL >> and the path from it to PHY isn't so clean which means there are some >> noise introduced by power-domain and other buses can't be filterd out >> by PHY and we could see noise from the frequency spectrum by oscilloscope. >> This makes the TX compatibility test a little difficult to pass the spec. >> So case(1) and case(2) are both used indeed now. If using case(2), we >> should disable RC's L0s support, and that is why we need this property to >> indicate this quirk. > > Doesn't the driver know which case it is using? I don't see why you need > the quirk property. Unfortunately it doesn't. This is one of the pre-input clock for PHY but doesn't get any indication from the register of both PHY and controller. So assigning a quirk seems quite straightforward. >> >> Also after checking quirk.c, I noticed there is already a quirk for >> disabling L0s unconditionally, quirk_disable_aspm_l0s. But obviously we >> shouldn't do that as mentioned above that case(1) could still works fine >> with L0s. > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Best Regards Shawn Lin
