linux-kernel - Re: [PATCH] PCI: amlogic: meson: Don't use FAST_LINK

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Date:   Sat, 09 May 2020 14:07:07 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     "yue.wang@...ogic.com" <yue.wang@...ogic.com>
Cc:     linux-pci <linux-pci@...r.kernel.org>,
        linux-amlogic <linux-amlogic@...ts.infradead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Kevin Hilman <khilman@...libre.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH] PCI: amlogic: meson: Don't use FAST_LINK_MODE to set up link

Hi Yue,

On Thu, 07 May 2020 02:43:31 +0100,
"yue.wang@...ogic.com" <yue.wang@...ogic.com> wrote:
> 
> [1  <text/plain; utf-8 (base64)>]
> Marc,
> 
> This patch looks all right. I tested in my meson board and pcie
> EP(QCA9888) worked well.
> 
> Fast link mode is enabled for simulation purposes, it should be
> disabled in the real hardware.

Thanks for confirming my reading of the manual and having tested it.
Can I take this as an "Acked-by:" and a "Tested-by:"?

Cheers,

	M.

>
> yue.wang@...ogic.com
>  
> From: Marc Zyngier
> Date: 2020-05-06 18:43
> To: linux-pci; linux-amlogic; linux-arm-kernel; linux-kernel; Kevin Hilman; Yue Wang
> CC: Bjorn Helgaas; Rob Herring; Lorenzo Pieralisi
> Subject: Re: [PATCH] PCI: amlogic: meson: Don't use FAST_LINK_MODE to set up link
> On Wed, 29 Apr 2020 17:42:30 +0100
> Marc Zyngier <maz@...nel.org> wrote:
>  
> > My vim3l board stubbornly refuses to play ball with a bog
> > standard PCIe switch (ASM1184e), spitting all kind of errors
> > ranging from link never coming up to crazy things like downstream
> > ports falling off the face of the planet.
> > 
> > Upon investigating how the PCIe RC is configured, I found the
> > following nugget: the Sysnopsys DWC PCIe Reference Manual, in the
> > section dedicated to the PLCR register, describes bit 7 (FAST_LINK_MODE)
> > as:
> > 
> > "Sets all internal timers to fast mode for simulation purposes."
> > 
> > I completely understand the need for setting this bit from a simulation
> > perspective, but what I have on my desk is actual silicon, which
> > expects timers to have a nominal value (and I expect this is the
> > case for most people).
> > 
> > Making sure the FAST_LINK_MODE bit is cleared when configuring the RC
> > solves this problem.
> > 
> > Fixes: 9c0ef6d34fdb ("PCI: amlogic: Add the Amlogic Meson PCIe controller driver")
> > Signed-off-by: Marc Zyngier <maz@...nel.org>
> > ---
> >  drivers/pci/controller/dwc/pci-meson.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pci-meson.c b/drivers/pci/controller/dwc/pci-meson.c
> > index 3715dceca1bf..ca59ba9e0ecd 100644
> > --- a/drivers/pci/controller/dwc/pci-meson.c
> > +++ b/drivers/pci/controller/dwc/pci-meson.c
> > @@ -289,11 +289,11 @@ static void meson_pcie_init_dw(struct meson_pcie *mp)
> >  meson_cfg_writel(mp, val, PCIE_CFG0);
> >  
> >  val = meson_elb_readl(mp, PCIE_PORT_LINK_CTRL_OFF);
> > - val &= ~LINK_CAPABLE_MASK;
> > + val &= ~(LINK_CAPABLE_MASK | FAST_LINK_MODE);
> >  meson_elb_writel(mp, val, PCIE_PORT_LINK_CTRL_OFF);
> >  
> >  val = meson_elb_readl(mp, PCIE_PORT_LINK_CTRL_OFF);
> > - val |= LINK_CAPABLE_X1 | FAST_LINK_MODE;
> > + val |= LINK_CAPABLE_X1;
> >  meson_elb_writel(mp, val, PCIE_PORT_LINK_CTRL_OFF);
> >  
> >  val = meson_elb_readl(mp, PCIE_GEN2_CTRL_OFF);
>  
> Yue, Kevin: any comment on this?
>  
> I found that the issue is reproducible even without a PCIe switch,
> depending on the single device I plug in this machine (an Intel SSD
> works fine, while a Marvell Ethernet adapter never shows up) as the
> LTSSM times out much earlier than it really should (HW timers running
> too quickly). Applying this patch makes every single device I have
> lying around work fine.
>  
> Thanks,
>  
> M.
> -- 
> Jazz is not dead. It just smells funny...
>  
> [2  <text/html; utf-8 (quoted-printable)>]

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