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Date: Tue, 21 Jun 2022 23:05:17 +0200
From: Robert Marko <robimarko@...il.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: svarbanov@...sol.com, Andy Gross <agross@...nel.org>,
Bjorn Andersson <bjorn.andersson@...aro.org>,
lpieralisi@...nel.org, Rob Herring <robh@...nel.org>, kw@...ux.com,
Bjorn Helgaas <bhelgaas@...gle.com>, p.zabel@...gutronix.de,
jingoohan1@...il.com, linux-pci@...r.kernel.org,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>,
johan+linaro@...nel.org
Subject: Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support
On Tue, 21 Jun 2022 at 22:32, Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Tue, Jun 21, 2022 at 01:23:30PM +0200, Robert Marko wrote:
> > IPQ8074 has one Gen2 and one Gen3 port, currently the Gen2 port will
> > cause the system to hang as its using DBI registers in the .init
> > and those are only accesible after phy_power_on().
>
> Is the fact that IPQ8074 has both a Gen2 and a Gen3 port relevant to
> this patch? I don't see the connection.
Hi Bjorn,
Not really, I can remove it from the description as this only affects the Gen2
port, Gen3 support is dependant on the IPQ6018 support getting merged as
it uses the same controller.
>
> I see that qcom_pcie_host_init() does:
>
> qcom_pcie_host_init
> pcie->cfg->ops->init(pcie)
> phy_power_on(pcie->phy)
> pcie->cfg->ops->post_init(pcie)
>
> and that you're moving DBI register accesses from
> qcom_pcie_init_2_3_3() to qcom_pcie_post_init_2_3_3().
>
> But I also see DBI register accesses in other .init() functions:
>
> qcom_pcie_init_2_1_0
> qcom_pcie_init_1_0_0 (oddly out of order)
> qcom_pcie_init_2_3_2
> qcom_pcie_init_2_4_0
>
> Why do these accesses not need to be moved? I assume it's because
> pcie->phy is an optional PHY and phy_power_on() does nothing on those
> controllers?
As far as I could figure out from QCA-s 5.4 kernel, various commits, and QCA-s
attempts to solve this already upstream the Gen2 controller in IPQ8074 is a bit
special and requires the PHY to be powered on before DBI could be accessed or
else the board will hang as it does for me.
I can only assume that this is an IPQ8074-specific quirk and other IP-s are not
affected like this, so they were not broken.
>
> Whatever the reason, I think the DBI accesses should be done
> consistently in .post_init(). I see that Dmitry's previous patches
> removed all those .post_init() functions, but I think the consistency
> is worth having.
>
> Perhaps we could reorder the patches so this patch comes first, moves
> the DBI accesses into .post_init(), then Dmitry's patches could be
> rebased on top to drop the clock handling?
>
> > So solve this by splitting the DBI read/writes to .post_init.
I am open to anything to get this fixed properly, you are gonna need
to point me in the right direction
as I am really new to PCI.
Regards,
Robert
> >
> > Fixes: a0fd361db8e5 ("PCI: dwc: Move "dbi", "dbi2", and "addr_space" resource setup into common code")
> > Signed-off-by: Robert Marko <robimarko@...il.com>
> > ---
> > Changes in v2:
> > * Rebase onto next-20220621
> > ---
> > drivers/pci/controller/dwc/pcie-qcom.c | 48 +++++++++++++++-----------
> > 1 file changed, 28 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index 51fed83484af..da6d79d61397 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -1061,9 +1061,7 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
> > struct qcom_pcie_resources_2_3_3 *res = &pcie->res.v2_3_3;
> > struct dw_pcie *pci = pcie->pci;
> > struct device *dev = pci->dev;
> > - u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> > int i, ret;
> > - u32 val;
> >
> > for (i = 0; i < ARRAY_SIZE(res->rst); i++) {
> > ret = reset_control_assert(res->rst[i]);
> > @@ -1120,6 +1118,33 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
> > goto err_clk_aux;
> > }
> >
> > + return 0;
> > +
> > +err_clk_aux:
> > + clk_disable_unprepare(res->ahb_clk);
> > +err_clk_ahb:
> > + clk_disable_unprepare(res->axi_s_clk);
> > +err_clk_axi_s:
> > + clk_disable_unprepare(res->axi_m_clk);
> > +err_clk_axi_m:
> > + clk_disable_unprepare(res->iface);
> > +err_clk_iface:
> > + /*
> > + * Not checking for failure, will anyway return
> > + * the original failure in 'ret'.
> > + */
> > + for (i = 0; i < ARRAY_SIZE(res->rst); i++)
> > + reset_control_assert(res->rst[i]);
> > +
> > + return ret;
> > +}
> > +
> > +static int qcom_pcie_post_init_2_3_3(struct qcom_pcie *pcie)
> > +{
> > + struct dw_pcie *pci = pcie->pci;
> > + u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> > + u32 val;
> > +
> > writel(SLV_ADDR_SPACE_SZ,
> > pcie->parf + PCIE20_v3_PARF_SLV_ADDR_SPACE_SIZE);
> >
> > @@ -1147,24 +1172,6 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
> > PCI_EXP_DEVCTL2);
> >
> > return 0;
> > -
> > -err_clk_aux:
> > - clk_disable_unprepare(res->ahb_clk);
> > -err_clk_ahb:
> > - clk_disable_unprepare(res->axi_s_clk);
> > -err_clk_axi_s:
> > - clk_disable_unprepare(res->axi_m_clk);
> > -err_clk_axi_m:
> > - clk_disable_unprepare(res->iface);
> > -err_clk_iface:
> > - /*
> > - * Not checking for failure, will anyway return
> > - * the original failure in 'ret'.
> > - */
> > - for (i = 0; i < ARRAY_SIZE(res->rst); i++)
> > - reset_control_assert(res->rst[i]);
> > -
> > - return ret;
> > }
> >
> > static int qcom_pcie_get_resources_2_7_0(struct qcom_pcie *pcie)
> > @@ -1598,6 +1605,7 @@ static const struct qcom_pcie_ops ops_2_4_0 = {
> > static const struct qcom_pcie_ops ops_2_3_3 = {
> > .get_resources = qcom_pcie_get_resources_2_3_3,
> > .init = qcom_pcie_init_2_3_3,
> > + .post_init = qcom_pcie_post_init_2_3_3,
> > .deinit = qcom_pcie_deinit_2_3_3,
> > .ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
> > };
> > --
> > 2.36.1
> >
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