RE: [PATCH v2] PCI: dwc: Add support to add GEN3 related equalization quirks

["Pankaj Dubey" <pankaj.dubey@samsung.com>]

> -----Original Message-----
> From: Andrew Murray <andrew.murray@arm.com>
> Sent: Monday, September 16, 2019 3:46 PM
> To: Pankaj Dubey <pankaj.dubey@samsung.com>
> Cc: linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org;
> jingoohan1@gmail.com; gustavo.pimentel@synopsys.com;
> lorenzo.pieralisi@arm.com; bhelgaas@google.com; Anvesh Salveru
> <anvesh.s@samsung.com>
> Subject: Re: [PATCH v2] PCI: dwc: Add support to add GEN3 related
equalization
> quirks
> 
> On Fri, Sep 13, 2019 at 04:09:50PM +0530, Pankaj Dubey wrote:
> > From: Anvesh Salveru <anvesh.s@samsung.com>
> >
> > In some platforms, PCIe PHY may have issues which will prevent linkup
> > to happen in GEN3 or higher speed. In case equalization fails, link
> > will fallback to GEN1.
> >
> > DesignWare controller gives flexibility to disable GEN3 equalization
> > completely or only phase 2 and 3 of equalization.
> >
> > This patch enables the DesignWare driver to disable the PCIe GEN3
> > equalization by enabling one of the following quirks:
> >  - DWC_EQUALIZATION_DISABLE: To disable GEN3 equalization all phases
> >  - DWC_EQ_PHASE_2_3_DISABLE: To disable GEN3 equalization phase 2 & 3
> >
> > Platform drivers can set these quirks via "quirk" variable of "dw_pcie"
> > struct.
> >
> > Signed-off-by: Anvesh Salveru <anvesh.s@samsung.com>
> > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > ---
> > Patchset v1 can be found at:
> >  - 1/2: https://lkml.org/lkml/2019/9/10/443
> >  - 2/2: https://lkml.org/lkml/2019/9/10/444
> >
> > Changes w.r.t v1:
> >  - Squashed two patches from v1 into one as suggested by Gustavo
> >  - Addressed review comments from Andrew
> >
> >  drivers/pci/controller/dwc/pcie-designware.c | 12 ++++++++++++
> > drivers/pci/controller/dwc/pcie-designware.h |  9 +++++++++
> >  2 files changed, 21 insertions(+)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.c
> > b/drivers/pci/controller/dwc/pcie-designware.c
> > index 7d25102..97fb18d 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > @@ -466,4 +466,16 @@ void dw_pcie_setup(struct dw_pcie *pci)
> >  		break;
> >  	}
> >  	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
> > +
> > +	if (pci->quirk & DWC_EQUALIZATION_DISABLE) {
> > +		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > +		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > +		dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > +	}
> > +
> > +	if (pci->quirk & DWC_EQ_PHASE_2_3_DISABLE) {
> > +		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > +		val |= PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE;
> > +		dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > +	}
> >  }
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.h
> > b/drivers/pci/controller/dwc/pcie-designware.h
> > index ffed084..e428b62 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > @@ -29,6 +29,10 @@
> >  #define LINK_WAIT_MAX_IATU_RETRIES	5
> >  #define LINK_WAIT_IATU			9
> >
> > +/* Parameters for GEN3 related quirks */
> > +#define DWC_EQUALIZATION_DISABLE	BIT(1)
> > +#define DWC_EQ_PHASE_2_3_DISABLE	BIT(2)
> > +
> >  /* Synopsys-specific PCIe configuration registers */
> >  #define PCIE_PORT_LINK_CONTROL		0x710
> >  #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
> > @@ -60,6 +64,10 @@
> >  #define PCIE_MSI_INTR0_MASK		0x82C
> >  #define PCIE_MSI_INTR0_STATUS		0x830
> >
> > +#define PCIE_PORT_GEN3_RELATED		0x890
> 
> I hadn't noticed this in the previous version - what is the proper name
for this
> register? Does it end in _RELATED?

As per SNPS databook the name of the register is "GEN3_RELATED_OFF". It is
port logic register so, to keep similarity with other port logic registers
in this file we named it as "PCIE_PORT_GEN3_RELATED". 

> 
> Thanks,
> 
> Andrew Murray
> 
> > +#define PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE	BIT(9)
> > +#define PORT_LOGIC_GEN3_EQ_DISABLE		BIT(16)
> > +
> >  #define PCIE_ATU_VIEWPORT		0x900
> >  #define PCIE_ATU_REGION_INBOUND		BIT(31)
> >  #define PCIE_ATU_REGION_OUTBOUND	0
> > @@ -244,6 +252,7 @@ struct dw_pcie {
> >  	struct dw_pcie_ep	ep;
> >  	const struct dw_pcie_ops *ops;
> >  	unsigned int		version;
> > +	unsigned int		quirk;
> >  };
> >
> >  #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie,
> > pp)
> > --
> > 2.7.4
> >