linux-kernel - R: [PATCH v5 11/11] PCI: qcom: Add Force GEN1 support

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Date:   Tue, 2 Jun 2020 19:07:27 +0200
From:   <ansuelsmth@...il.com>
To:     "'Bjorn Helgaas'" <helgaas@...nel.org>
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>
Subject: R: [PATCH v5 11/11] PCI: qcom: Add Force GEN1 support

> 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?


> > +		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
> >