RE: [RFC 2/2] PCI: imx6: Support more than Gen2 speed link mode

[Hongxing Zhu]

> -----Original Message-----
> From: Hongxing Zhu <hongxing.zhu@xxxxxxx>
> Sent: 2022年7月20日 9:44
> To: tharvey@xxxxxxxxxxxxx
> Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>; bhelgaas@xxxxxxxxxx; Lorenzo
> Pieralisi <lorenzo.pieralisi@xxxxxxx>; Fabio Estevam <festevam@xxxxxxxxx>;
> linux-pci@xxxxxxxxxxxxxxx; Linux ARM Mailing List
> <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; open list
> <linux-kernel@xxxxxxxxxxxxxxx>; Sascha Hauer <kernel@xxxxxxxxxxxxxx>;
> dl-linux-imx <linux-imx@xxxxxxx>
> Subject: RE: [RFC 2/2] PCI: imx6: Support more than Gen2 speed link mode
> 
> > -----Original Message-----
> > From: Tim Harvey <tharvey@xxxxxxxxxxxxx>
> > Sent: 2022年7月20日 8:59
> > To: Hongxing Zhu <hongxing.zhu@xxxxxxx>
> > Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>; bhelgaas@xxxxxxxxxx; Lorenzo
> > Pieralisi <lorenzo.pieralisi@xxxxxxx>; Fabio Estevam
> > <festevam@xxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx; Linux ARM Mailing
> > List <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; open list
> > <linux-kernel@xxxxxxxxxxxxxxx>; Sascha Hauer <kernel@xxxxxxxxxxxxxx>;
> > dl-linux-imx <linux-imx@xxxxxxx>
> > Subject: Re: [RFC 2/2] PCI: imx6: Support more than Gen2 speed link
> > mode
> >
> > On Wed, May 18, 2022 at 2:49 AM Richard Zhu <hongxing.zhu@xxxxxxx>
> > wrote:
> > >
> > > Support more than Gen2 speed link mode, since i.MX8MP PCIe supports
> > > up to Gen3 link speed.
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> > > ---
> > >  drivers/pci/controller/dwc/pci-imx6.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 30641d2dda14..37012f9a33a0 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -809,8 +809,8 @@ static int imx6_pcie_start_link(struct dw_pcie
> > > *pci)
> > >
> > >         dw_pcie_wait_for_link(pci);
> > >
> > > -       if (pci->link_gen == 2) {
> > > -               /* Allow Gen2 mode after the link is up. */
> > > +       if (pci->link_gen > 1) {
> > > +               /* Allow faster modes after the link is up. */
> > >                 dw_pcie_dbi_ro_wr_en(pci);
> > >                 tmp = dw_pcie_readl_dbi(pci, offset +
> PCI_EXP_LNKCAP);
> > >                 tmp &= ~PCI_EXP_LNKCAP_SLS;
> > > --
> >
> > Richard,
> >
> > I noticed that your imx8mp pcie series [1] will force the imx8mp to
> > link only at
> > gen1 speeds unless support like the above is added. I believe you
> > would also need the following:
> > -               tmp |= PCI_EXP_LNKCAP_SLS_5_0GB;
> > +               tmp |= pci->link_gen;
> >
> > When I used this along with your imx8mp series however I only get a gen1
> link.
> >
> > Have you made any progress on a v3 of your imx8mp series?
Missing one in previous reply.
I still didn't know how to encapsulate the PLL bits related operations of
 HSIOMIX to one clock suggested by Lucas [1].
[1] https://patchwork.ozlabs.org/project/linux-pci/patch/1646644054-24421-4-git-send-email-hongxing.zhu@xxxxxxx/
I'm prepare the i.MX EP RC patch-set reviewing, and plan to look at i.MX8MP
 series after the EP RC patch-set is settle down.

Best Regards
Richard Zhu
> >
> > Do you know if the downstream NXP vendor kernel [2] supports imx8mp
> > Gen3 links?
> Hi Tim:
> Thanks for your timely reminder. I just was puzzled a while why only Gen1 is
> linked up on i.MX8MP.
> Root cause is that I forget merge some local changes to the up-stream codes.
> BTW, the local codes supports the Gen3 link on i.MX8MP A1 chip or later.
> Since the A0 chip PCIe only supports up to Gen2 link speed.
> 
> Best Regards
> Richard Zhu
> 
> >
> > Best Regards,
> >
> > Tim
> > [1]
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatc
> > hw
> >
> ork.kernel.org%2Fproject%2Flinux-pci%2Flist%2F%3Fseries%3D620887%26sta
> >
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> > [2]
> >
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsource.
> >
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> >
> Chongxing.zhu%40nxp.com%7C9c7b11f2599645f62dd608da69eb1455%7C68
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> > 6%2FtRjJMHOOHcm7Jb1BXwGi%2FVnLnWmKCeNeo4%3D&amp;reserved=0