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

[Andrew Murray <andrew.murray@arm.com>]

On Mon, Oct 21, 2019 at 07:56:55PM +0530, Pankaj Dubey wrote:
> 
> 
> > -----Original Message-----
> > From: Andrew Murray <andrew.murray@arm.com>
> > Sent: Monday, October 21, 2019 7:47 PM
> > To: Pankaj Dubey <pankaj.dubey@samsung.com>
> > Cc: 'Anvesh Salveru' <anvesh.s@samsung.com>; linux-pci@vger.kernel.org;
> > linux-kernel@vger.kernel.org; bhelgaas@google.com;
> > gustavo.pimentel@synopsys.com; jingoohan1@gmail.com;
> > lorenzo.pieralisi@arm.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@arm.com>
> > > > Sent: Monday, October 21, 2019 7:34 PM
> > > > To: Anvesh Salveru <anvesh.s@samsung.com>
> > > > Cc: linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org;
> > > > bhelgaas@google.com; gustavo.pimentel@synopsys.com;
> > > > jingoohan1@gmail.com; lorenzo.pieralisi@arm.com; Pankaj Dubey
> > > > <pankaj.dubey@samsung.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@samsung.com>
> > > > > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.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?
> > 
> 
> Yes. We have one internal PCIe RC driver (which we can't disclose/upstream
> right now) has this issue and currently we are handling it using this DT
> binding. So we would like to upstream common code, so other platform's
> driver can use this.

Ah, I understand.

Thanks,

Andrew Murray

> 
> > > 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
> > > > >
> > >
>