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SubjectRE: [PATCH 2/2] PCI: dwc: Add support to disable equalization phase 2 and 3
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> From: Andrew Murray <andrew.murray@arm.com>
>
> On Tue, Sep 10, 2019 at 09:51:41PM +0530, Pankaj Dubey wrote:
> > On Tue, 10 Sep 2019 at 19:59, Andrew Murray <andrew.murray@arm.com>
> wrote:
> > >
> > > On Tue, Sep 10, 2019 at 05:55:02PM +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 high 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.
> > >
> > > Do some platforms have issues conducting phase 2 and 3 when they
> > > successfully conduct phase 0 and 1?
> > >
> >
> > Yes, it is possible.
> >
> > > >
> > > > Platform drivers can disable equalization phase 2 and 3, by
> > > > setting dwc_pci_quirk flag DWC_EQUALIZATION_DISABLE.
> > > >
> > > > 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 | 3 +++
> > > > drivers/pci/controller/dwc/pcie-designware.h | 2 ++
> > > > 2 files changed, 5 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c
> > > > b/drivers/pci/controller/dwc/pcie-designware.c
> > > > index bf82091..97a8268 100644
> > > > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > > > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > > > @@ -472,5 +472,8 @@ void dw_pcie_setup(struct dw_pcie *pci)
> > > > if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE)
> > > > val |= PORT_LOGIC_GEN3_EQ_DISABLE;
> > > >
> > > > + if (pci->dwc_pci_quirk & DWC_EQ_PHASE_2_3_DISABLE)
> > > > + val |= PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE;
> > > > +
>
> Also is it harmless to set both DWC_EQUALIZATION_DISABLE and
> DWC_EQ_PHASE_2_3_DISABLE? (Which is permitted here).
>

Yes, it will be harmless.

> Thanks,
>
> Andrew Murray
>
> > > > 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 a1453c5..b541508 100644
> > > > --- a/drivers/pci/controller/dwc/pcie-designware.h
> > > > +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > > > @@ -31,6 +31,7 @@
> > > >
> > > > /* Parameters for PCIe Quirks */
> > > > #define DWC_EQUALIZATION_DISABLE 0x1
> > > > +#define DWC_EQ_PHASE_2_3_DISABLE 0x2
> > >
> > > It only makes sense for either DWC_EQUALIZATION_DISABLE or
> > > DWC_EQ_PHASE_2_3_DISABLE to be specified, though if dwc_pci_quirk
> > > intends to hold other quirks should these be numbers and not bit
fields?
> > >
> > Yes, you are right in a given platform it will be either
> > DWC_EQUALIZATION_DISABLE or DWC_EQ_PHASE_2_3_DISABLE.
> >
> > Intention behind making it bit-field was to add other quirks in future.
> >
> > > Thanks,
> > >
> > > Andrew Murray
> > >
> > > >
> > > > /* Synopsys-specific PCIe configuration registers */
> > > > #define PCIE_PORT_LINK_CONTROL 0x710
> > > > @@ -65,6 +66,7 @@
> > > >
> > > > #define PCIE_PORT_GEN3_RELATED 0x890
> > > > #define PORT_LOGIC_GEN3_EQ_DISABLE BIT(16)
> > > > +#define PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE BIT(9)
> > > >
> > > > #define PCIE_ATU_VIEWPORT 0x900
> > > > #define PCIE_ATU_REGION_INBOUND BIT(31)
> > > > --
> > > > 2.7.4
> > > >

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