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.
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Best Regards
Shawn Lin
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