linux-kernel - Re: [PATCH 2/2] PCI: dwc: Add support to handle ZRX-DC Compliant PHYs

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Message-ID: <20191021141714.GT47056@e119886-lin.cambridge.arm.com>
Date:   Mon, 21 Oct 2019 15:17:14 +0100
From:   Andrew Murray <andrew.murray@....com>
To:     Pankaj Dubey <pankaj.dubey@...sung.com>
Cc:     'Anvesh Salveru' <anvesh.s@...sung.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, bhelgaas@...gle.com,
        gustavo.pimentel@...opsys.com, jingoohan1@...il.com,
        lorenzo.pieralisi@....com
Subject: Re: [PATCH 2/2] PCI: dwc: Add support to handle ZRX-DC Compliant PHYs

On Mon, Oct 21, 2019 at 07:44:25PM +0530, Pankaj Dubey wrote:
> 
> 
> > -----Original Message-----
> > From: Andrew Murray <andrew.murray@....com>
> > Sent: Monday, October 21, 2019 7:34 PM
> > To: Anvesh Salveru <anvesh.s@...sung.com>
> > Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org;
> > bhelgaas@...gle.com; gustavo.pimentel@...opsys.com;
> > jingoohan1@...il.com; lorenzo.pieralisi@....com; Pankaj Dubey
> > <pankaj.dubey@...sung.com>
> > Subject: Re: [PATCH 2/2] PCI: dwc: Add support to handle ZRX-DC Compliant
> > PHYs
> > 
> > On Mon, Oct 21, 2019 at 05:59:53PM +0530, Anvesh Salveru wrote:
> > > Many platforms use DesignWare controller but the PHY can be different
> > > in different platforms. If the PHY is compliant is to ZRX-DC
> > > specification
> > 
> > s/is to/to the/
> 
> OK
> 
> > 
> > > it helps in low power consumption during power states.
> > 
> > s/in low/lower/
> > 
> OK
> > >
> > > If current data rate is 8.0 GT/s or higher and PHY is not compliant to
> > > ZRX-DC specification, then after every 100ms link should transition to
> > > recovery state during the low power states.
> > >
> > > DesignWare controller provides GEN3_ZRXDC_NONCOMPL field in
> > > GEN3_RELATED_OFF to specify about ZRX-DC compliant PHY.
> > >
> > > Platforms with ZRX-DC compliant PHY can set "snps,phy-zrxdc-compliant"
> > > property in controller DT node to specify this property to the
> controller.
> > >
> > > Signed-off-by: Anvesh Salveru <anvesh.s@...sung.com>
> > > Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++
> > > drivers/pci/controller/dwc/pcie-designware.h | 3 +++
> > >  2 files changed, 10 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c
> > > b/drivers/pci/controller/dwc/pcie-designware.c
> > > index 820488dfeaed..6560d9f765d7 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > > @@ -556,4 +556,11 @@ void dw_pcie_setup(struct dw_pcie *pci)
> > >  		       PCIE_PL_CHK_REG_CHK_REG_START;
> > >  		dw_pcie_writel_dbi(pci, PCIE_PL_CHK_REG_CONTROL_STATUS,
> > val);
> > >  	}
> > > +
> > > +	if (of_property_read_bool(np, "snps,phy-zrxdc-compliant")) {
> > > +		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
> > > +		val &= ~PORT_LOGIC_GEN3_ZRXDC_NONCOMPL;
> > > +		dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
> > > +	}
> > > +
> > 
> > Given that this duplicates tegra_pcie_prepare_host in pcie-tegra194.c, can
> we
> > update that driver to adopt this new binding?
> > 
> 
> Yes, Thanks for highlighting this. Otherwise I was worried that we have one
> more patch without real user :)

Indeed :|

Though besides Tegra, is there any other reason you are adding this?

> We will update pcie-tegra194.c driver and post the patch to adopt this
> binding.

It's much appreciated.

Andrew Murray

> 
> > Thanks,
> > 
> > Andrew Murray
> > 
> > >  }
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware.h
> > > b/drivers/pci/controller/dwc/pcie-designware.h
> > > index 5a18e94e52c8..427a55ec43c6 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > > @@ -60,6 +60,9 @@
> > >  #define PCIE_MSI_INTR0_MASK		0x82C
> > >  #define PCIE_MSI_INTR0_STATUS		0x830
> > >
> > > +#define PCIE_PORT_GEN3_RELATED		0x890
> > > +#define PORT_LOGIC_GEN3_ZRXDC_NONCOMPL		BIT(0)
> > > +
> > >  #define PCIE_ATU_VIEWPORT		0x900
> > >  #define PCIE_ATU_REGION_INBOUND		BIT(31)
> > >  #define PCIE_ATU_REGION_OUTBOUND	0
> > > --
> > > 2.17.1
> > >
>