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Date: Tue, 2 Jun 2020 12:28:21 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: ansuelsmth@...il.com
Cc: 'Rob Herring' <robh+dt@...nel.org>,
'Sham Muthayyan' <smuthayy@...eaurora.org>,
'Rob Herring' <robh@...nel.org>,
'Andy Gross' <agross@...nel.org>,
'Bjorn Andersson' <bjorn.andersson@...aro.org>,
'Bjorn Helgaas' <bhelgaas@...gle.com>,
'Mark Rutland' <mark.rutland@....com>,
'Stanimir Varbanov' <svarbanov@...sol.com>,
'Lorenzo Pieralisi' <lorenzo.pieralisi@....com>,
'Andrew Murray' <amurray@...goodpenguin.co.uk>,
'Philipp Zabel' <p.zabel@...gutronix.de>,
linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
Varadarajan Narayanan <varada@...eaurora.org>
Subject: Re: R: [PATCH v5 11/11] PCI: qcom: Add Force GEN1 support
[+cc Varada]
On Tue, Jun 02, 2020 at 07:07:27PM +0200, ansuelsmth@...il.com wrote:
> > On Tue, Jun 02, 2020 at 01:53:52PM +0200, Ansuel Smith wrote:
> > > From: Sham Muthayyan <smuthayy@...eaurora.org>
> > >
> > > Add Force GEN1 support needed in some ipq8064 board that needs to
> > limit
> > > some PCIe line to gen1 for some hardware limitation. This is set by the
> > > max-link-speed binding and needed by some soc based on ipq8064. (for
> > > example Netgear R7800 router)
> > >
> > > Signed-off-by: Sham Muthayyan <smuthayy@...eaurora.org>
> > > Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> > > Reviewed-by: Rob Herring <robh@...nel.org>
> > > ---
> > > drivers/pci/controller/dwc/pcie-qcom.c | 13 +++++++++++++
> > > 1 file changed, 13 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c
> > b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index 259b627bf890..0ce15d53c46e 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -27,6 +27,7 @@
> > > #include <linux/slab.h>
> > > #include <linux/types.h>
> > >
> > > +#include "../../pci.h"
> > > #include "pcie-designware.h"
> > >
> > > #define PCIE20_PARF_SYS_CTRL 0x00
> > > @@ -99,6 +100,8 @@
> > > #define PCIE20_v3_PARF_SLV_ADDR_SPACE_SIZE 0x358
> > > #define SLV_ADDR_SPACE_SZ 0x10000000
> > >
> > > +#define PCIE20_LNK_CONTROL2_LINK_STATUS2 0xa0
> > > +
> > > #define DEVICE_TYPE_RC 0x4
> > >
> > > #define QCOM_PCIE_2_1_0_MAX_SUPPLY 3
> > > @@ -195,6 +198,7 @@ struct qcom_pcie {
> > > struct phy *phy;
> > > struct gpio_desc *reset;
> > > const struct qcom_pcie_ops *ops;
> > > + int gen;
> > > };
> > >
> > > #define to_qcom_pcie(x) dev_get_drvdata((x)->dev)
> > > @@ -395,6 +399,11 @@ static int qcom_pcie_init_2_1_0(struct
> > qcom_pcie *pcie)
> > > /* wait for clock acquisition */
> > > usleep_range(1000, 1500);
> > >
> > > + if (pcie->gen == 1) {
> > > + val = readl(pci->dbi_base +
> > PCIE20_LNK_CONTROL2_LINK_STATUS2);
> > > + val |= 1;
> >
> > Is this the same bit that's visible in config space as
> > PCI_EXP_LNKSTA_CLS_2_5GB? Why not use that #define?
> >
> > There are a bunch of other #defines in this file that look like
> > redefinitions of standard things:
> >
> > #define PCIE20_COMMAND_STATUS 0x04
> > Looks like PCI_COMMAND
> >
> > #define CMD_BME_VAL 0x4
> > Looks like PCI_COMMAND_MASTER
> >
> > #define PCIE20_DEVICE_CONTROL2_STATUS2 0x98
> > Looks like (PCIE20_CAP + PCI_EXP_DEVCTL2)
> >
> > #define PCIE_CAP_CPL_TIMEOUT_DISABLE 0x10
> > Looks like PCI_EXP_DEVCTL2_COMP_TMOUT_DIS
> >
> > #define PCIE20_CAP 0x70
> > This one is obviously device-specific
> >
> > #define PCIE20_CAP_LINK_CAPABILITIES (PCIE20_CAP + 0xC)
> > Looks like (PCIE20_CAP + PCI_EXP_LNKCAP)
> >
> > #define PCIE20_CAP_ACTIVE_STATE_LINK_PM_SUPPORT (BIT(10) |
> > BIT(11))
> > Looks like PCI_EXP_LNKCAP_ASPMS
> >
> > #define PCIE20_CAP_LINK_1 (PCIE20_CAP + 0x14)
> > #define PCIE_CAP_LINK1_VAL 0x2FD7F
> > This looks like PCIE20_CAP_LINK_1 should be (PCIE20_CAP +
> > PCI_EXP_SLTCAP), but "CAP_LINK_1" doesn't sound like the Slot
> > Capabilities register, and I don't know what PCIE_CAP_LINK1_VAL
> > means.
>
> The define are used by ipq8074 and I really can't test the changes.
> Anyway it shouldn't make a difference use the define instead of the
> custom value so a patch should not harm anything... Problem is the
> last 2 define that we really don't know what they are about... How
> should I proceed? Change only the value related to
> PCI_EXP_LNKSTA_CLS_2_5GB or change all the other except the last 2?
I personally would change all the ones I mentioned above (in a
separate patch from the one that adds "max-link-speed" support).
Testing isn't a big deal because changing the #defines shouldn't
change the generated code at all.
PCIE20_CAP_LINK_1 / PCIE_CAP_LINK1_VAL looks like a potential bug or
at least a very misleading name. I wouldn't touch it unless we can
figure out what's going on.
Looks like most of this was added by 5d76117f070d ("PCI: qcom: Add
support for IPQ8074 PCIe controller"). Shame on me for not asking
these questions at the time.
Sham, Varada, can you shed any light on PCIE20_CAP_LINK_1 and
PCIE_CAP_LINK1_VAL?
> > > + writel(val, pci->dbi_base +
> > PCIE20_LNK_CONTROL2_LINK_STATUS2);
> > > + }
> > >
> > > /* Set the Max TLP size to 2K, instead of using default of 4K */
> > > writel(CFG_REMOTE_RD_REQ_BRIDGE_SIZE_2K,
> > > @@ -1397,6 +1406,10 @@ static int qcom_pcie_probe(struct
> > platform_device *pdev)
> > > goto err_pm_runtime_put;
> > > }
> > >
> > > + pcie->gen = of_pci_get_max_link_speed(pdev->dev.of_node);
> > > + if (pcie->gen < 0)
> > > + pcie->gen = 2;
> > > +
> > > res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
> > "parf");
> > > pcie->parf = devm_ioremap_resource(dev, res);
> > > if (IS_ERR(pcie->parf)) {
> > > --
> > > 2.25.1
> > >
>
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