It's okay for me too. Acked-by: Richard Zhu <Richard.Zhu@xxxxxxxxxxxxx> Thanks Tim. Freescale Linux BSP team Best Regards Richard Zhu -----Original Message----- From: Fabio Estevam [mailto:festevam@xxxxxxxxx] Sent: Thursday, November 05, 2015 11:41 PM To: Tim Harvey Cc: Lucas Stach; Bjorn Helgaas; linux-pci@xxxxxxxxxxxxxxx; Estevam Fabio-R49496; Zhu Richard-R65037 Subject: Re: [PATCH RFC] PCI: imx6: add dt prop for link gen, default to gen1 [Adding Richard Zhu] On Thu, Nov 5, 2015 at 12:58 PM, Tim Harvey <tharvey@xxxxxxxxxxxxx> wrote: > Freescale has stated [1] that the LVDS clock source of the IMX6 does > not pass the PCI Gen2 clock jitter test, therefore unless an external > Gen2 compliant external clock source is present and supplied back to > the IMX6 PCIe core via LVDS CLK1/CLK2 you can not claim Gen2 compliance. > > Add a dt property to specify gen1 vs gen2 and check this before > allowing a Gen2 link. > > We default to Gen1 if the property is not present because at this time > there are no IMX6 boards in mainline that 'input' a clock on LVDS CLK1/CLK2. > > In order to be Gen2 compliant on IMX6 you need to: > - have a Gen2 compliant external clock generator and route that clock back > to either LVDS CLK1 or LVDS CLK2 as an input. > (see IMX6SX-SabreSD reference design) > - specify this clock in the pcie node in the dt > (ie IMX6QDL_CLK_LVDS1_IN or IMX6QDL_CLK_LVDS2_IN instead of > IMX6QDL_CLK_LVDS1_GATE which configures it as a CLK output) > > [1] https://community.freescale.com/message/453209 > > Signed-off-by: Tim Harvey <tharvey@xxxxxxxxxxxxx> > > This is an RFC because I'm assuming the decision to default to Gen1 > link only is going to ruffle some feathers. My understanding is that > if you do not use an external Gen2 compliant clockgen for > peripepherals 'and' the IMX6 core you should not claim Gen2 > compliance. This was not obvious on original IMX6 reference designs > and I believe the jitter issue was discovered by Freescale later and > future reference designs were modified to state you need an ext clockgen for Gen2 compliance. Looks good to me: Reviewed-by: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx> ��.n��������+%������w��{.n�����{���"�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
