linux-kernel - Re: [PATCH] pcie: ti: Provide patch to force GEN1 PCIe operation

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Date:   Mon, 16 Jan 2017 07:49:27 +0100
From:   Lukasz Majewski <lukma@...x.de>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jingoo Han <jingoohan1@...il.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        <linux-omap@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] pcie: ti: Provide patch to force GEN1 PCIe operation

Hi Kishon,

> Hi,
> 
> On Sunday 15 January 2017 06:49 PM, Lukasz Majewski wrote:
> > Some devices (due to e.g. bad PCIe signal integrity) require to run
> > with forced GEN1 speed on PCIe bus.
> > 
> > This patch changes the speed explicitly on dra7 based devices when
> > proper device tree attribute is defined for the PCIe controller.
> > 
> > Signed-off-by: Lukasz Majewski <lukma@...x.de>
> 
> Bjorn has already queued a patch to do the same thing
> https://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/log/?h=pci/host-dra7xx

It seems like Bjorn only modifies CAP registers.

He also needs to change register with 0x080C offset to actually
( PCIECTRL_PL_WIDTH_SPEED_CTL )

Best regards,
Łukasz

> 
> Thanks
> Kishon
> 
> > ---
> > 
> > Patch applies on newest origin/master
> > SHA1: f4d3935e4f4884ba80561db5549394afb8eef8f7
> > 
> > Tested at AM5728
> > 
> > ---
> >  Documentation/devicetree/bindings/pci/ti-pci.txt |  1 +
> >  drivers/pci/host/pci-dra7xx.c                    | 23
> > +++++++++++++++++++++++
> > drivers/pci/host/pcie-designware.h               |  1 + 3 files
> > changed, 25 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/pci/ti-pci.txt
> > b/Documentation/devicetree/bindings/pci/ti-pci.txt index
> > 60e2516..9f97409 100644 ---
> > a/Documentation/devicetree/bindings/pci/ti-pci.txt +++
> > b/Documentation/devicetree/bindings/pci/ti-pci.txt @@ -25,6 +25,7
> > @@ PCIe Designware Controller 
> >  Optional Property:
> >   - gpios : Should be added if a gpio line is required to drive
> > PERST# line
> > + - to,pcie-is-gen1: Indicates that forced gen1 port operation is
> > needed. 
> >  Example:
> >  axi {
> > diff --git a/drivers/pci/host/pci-dra7xx.c
> > b/drivers/pci/host/pci-dra7xx.c index 9595fad..eec5fae 100644
> > --- a/drivers/pci/host/pci-dra7xx.c
> > +++
> > b/drivers/pci/host/pci-https://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/log/?h=pci/host-dra7xxdra7xx.c
> > @@ -63,6 +63,13 @@ #define
> > LINK_UP						BIT(16)
> > #define
> > DRA7XX_CPU_TO_BUS_ADDR				0x0FFFFFFF
> > +#define         PCIECTRL_EP_DBICS_LNK_CAP
> > 0x007C +#define
> > MAX_LINK_SPEEDS_MASK				GENMASK(3, 0)
> > +#define         MAX_LINK_SPEEDS_GEN1
> > BIT(0) + +#define
> > PCIECTRL_PL_WIDTH_SPEED_CTL                     0x080C
> > +#define         CFG_DIRECTED_SPEED_CHANGE
> > BIT(17) + struct dra7xx_pcie { struct pcie_port	pp;
> >  	void __iomem		*base;		/* DT
> > ti_conf */ @@ -270,6 +277,7 @@ static int __init
> > dra7xx_add_pcie_port(struct dra7xx_pcie *dra7xx, struct pcie_port
> > *pp = &dra7xx->pp; struct device *dev = pp->dev;
> >  	struct resource *res;
> > +	u32 val;
> >  
> >  	pp->irq = platform_get_irq(pdev, 1);
> >  	if (pp->irq < 0) {
> > @@ -296,6 +304,18 @@ static int __init dra7xx_add_pcie_port(struct
> > dra7xx_pcie *dra7xx, if (!pp->dbi_base)
> >  		return -ENOMEM;
> >  
> > +	if (pp->is_gen1) {
> > +		dev_info(dev, "GEN1 forced\n");
> > +
> > +		val = readl(pp->dbi_base +
> > PCIECTRL_EP_DBICS_LNK_CAP);
> > +		set_mask_bits(&val, MAX_LINK_SPEEDS_MASK,
> > MAX_LINK_SPEEDS_GEN1);
> > +		writel(val, pp->dbi_base +
> > PCIECTRL_EP_DBICS_LNK_CAP); +
> > +		val = readl(pp->dbi_base +
> > PCIECTRL_PL_WIDTH_SPEED_CTL);
> > +		val &= ~CFG_DIRECTED_SPEED_CHANGE;
> > +		writel(val, pp->dbi_base +
> > PCIECTRL_PL_WIDTH_SPEED_CTL);
> > +	}
> > +
> >  	ret = dw_pcie_host_init(pp);
> >  	if (ret) {
> >  		dev_err(dev, "failed to initialize host\n");
> > @@ -404,6 +424,9 @@ static int __init dra7xx_pcie_probe(struct
> > platform_device *pdev) goto err_gpio;
> >  	}
> >  
> > +	if (of_property_read_bool(np, "ti,pcie-is-gen1"))
> > +		pp->is_gen1 = true;
> > +
> >  	reg = dra7xx_pcie_readl(dra7xx,
> > PCIECTRL_DRA7XX_CONF_DEVICE_CMD); reg &= ~LTSSM_EN;
> >  	dra7xx_pcie_writel(dra7xx,
> > PCIECTRL_DRA7XX_CONF_DEVICE_CMD, reg); diff --git
> > a/drivers/pci/host/pcie-designware.h
> > b/drivers/pci/host/pcie-designware.h index a567ea2..2fb0b18 100644
> > --- a/drivers/pci/host/pcie-designware.h +++
> > b/drivers/pci/host/pcie-designware.h @@ -50,6 +50,7 @@ struct
> > pcie_port { struct irq_domain	*irq_domain;
> >  	unsigned long		msi_data;
> >  	u8			iatu_unroll_enabled;
> > +	u8                      is_gen1;
> >  	DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS);
> >  };
> >  
> > 




Best regards,

Lukasz Majewski

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