[<prev] [next>] [day] [month] [year] [list]
Message-ID: <472ebdbe8575b99ac8191e626a87814b88e21c31.camel@mediatek.com>
Date: Fri, 13 Oct 2023 08:31:19 +0000
From: Jianjun Wang (王建军)
<Jianjun.Wang@...iatek.com>
To: "daniel@...rotopia.org" <daniel@...rotopia.org>,
"linux@...web.de" <linux@...web.de>,
"helgaas@...nel.org" <helgaas@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mediatek@...ts.infradead.org"
<linux-mediatek@...ts.infradead.org>,
"john@...ozen.org" <john@...ozen.org>,
"ansuelsmth@...il.com" <ansuelsmth@...il.com>,
"robh@...nel.org" <robh@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"lpieralisi@...nel.org" <lpieralisi@...nel.org>,
"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
"angelogioacchino.delregno@...labora.com"
<angelogioacchino.delregno@...labora.com>,
Ryder Lee <Ryder.Lee@...iatek.com>
Subject: Re: [PATCH] PCI: mediatek-gen3: fix PCIe #PERST being de-asserted too
early
On Tue, 2023-10-10 at 18:42 +0200, Frank Wunderlich wrote:
>
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> Am 10. Oktober 2023 18:04:23 MESZ schrieb Bjorn Helgaas <
> helgaas@...nel.org>:
> > On Fri, Oct 06, 2023 at 09:45:58AM +0200, Daniel Golle wrote:
> > > The driver for MediaTek gen3 PCIe hosts de-asserts all reset
> > > signals at the same time using a single register write operation.
> > > Delay the de-assertion of the #PERST signal by 100ms as required
> > > by
> > > PCIe CEM clause 2.2, some PCIe devices fail to come up otherwise.
> > >
> > > Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> > > drivers/pci/controller/pcie-mediatek-gen3.c | 8 +++++++-
> > > 1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c
> > > b/drivers/pci/controller/pcie-mediatek-gen3.c
> > > index e0e27645fdf4..ba8cfce03aad 100644
> > > --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> > > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> > > @@ -350,7 +350,13 @@ static int mtk_pcie_startup_port(struct
> > > mtk_gen3_pcie *pcie)
> > >
> >
> > I feel like I'm missing something because this patch seems to be
> > adding a delay for T_PVPERL, but the comment before the existing
> > msleep() claims *it* is the T_PVPERL delay:
> >
> > * Described in PCIe CEM specification sections 2.2 (PERST#
> > Signal)
> > * and 2.2.1 (Initial Power-Up (G3 to S0)).
> > * The deassertion of PERST# should be delayed 100ms
> > (TPVPERL)
> > * for the power and clock to become stable.
> >
> > > msleep(100);
> > >
> > > /* De-assert reset signals */
> > > - val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB |
> > > PCIE_PE_RSTB);
> > > + val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB);
> > > + writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
> > > +
> > > + msleep(100);
> > >
> >
> > So I'm confused about these two sleeps. Are they for different
> > parameters?
> >
> > T_PVPERL is defined from "Power stable to PERST# inactive". Do we
> > have any actual indication of when to start that delay, i.e., do we
> > have a clue about when power became stable?
> >
> > > + /* De-assert PERST# signals */
> > > + val &= ~(PCIE_PE_RSTB);
> > > writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG);
> > >
> > > /* Check if the link is up or not */
> > > --
> > > 2.42.0
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
> Hi
>
> Seems it is same as the patch i've sent some time ago and which was
> rejected because of the additional delay...
>
>
https://patchwork.kernel.org/project/linux-mediatek/patch/20230402131347.99268-1-linux@fw-web.de/
>
> Or am i wrong?
> regards Frank
Hi Daniel,
Did you found this issue on MT7986(BPI-R3) or other platforms?
Can you share the PCIe device model that failed to link up?
Thanks.
Powered by blists - more mailing lists