linux-kernel - Re: [PATCH v3 1/3] PCI: qcom: Enable cache coherency for SA8775P RC

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Date:   Fri, 17 Nov 2023 13:40:25 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Mrinmay Sarkar <quic_msarkar@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, konrad.dybcio@...aro.org, robh+dt@...nel.org,
        quic_shazhuss@...cinc.com, quic_nitegupt@...cinc.com,
        quic_ramkri@...cinc.com, quic_nayiluri@...cinc.com,
        robh@...nel.org, quic_krichai@...cinc.com,
        quic_vbadigan@...cinc.com, quic_parass@...cinc.com,
        quic_schintav@...cinc.com, quic_shijjose@...cinc.com,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v3 1/3] PCI: qcom: Enable cache coherency for SA8775P RC

On Wed, Nov 15, 2023 at 03:21:26PM +0200, Dmitry Baryshkov wrote:
> On Wed, 15 Nov 2023 at 15:18, Dmitry Baryshkov
> <dmitry.baryshkov@...aro.org> wrote:
> >
> > On Wed, 15 Nov 2023 at 14:37, Mrinmay Sarkar <quic_msarkar@...cinc.com> wrote:
> > >
> > > This change will enable cache snooping logic to support
> > > cache coherency for 8775 RC platform.
> > >
> > > Signed-off-by: Mrinmay Sarkar <quic_msarkar@...cinc.com>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-qcom.c | 13 +++++++++++++
> > >  1 file changed, 13 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index 6902e97..b82ccd1 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -51,6 +51,7 @@
> > >  #define PARF_SID_OFFSET                                0x234
> > >  #define PARF_BDF_TRANSLATE_CFG                 0x24c
> > >  #define PARF_SLV_ADDR_SPACE_SIZE               0x358
> > > +#define PCIE_PARF_NO_SNOOP_OVERIDE             0x3d4
> > >  #define PARF_DEVICE_TYPE                       0x1000
> > >  #define PARF_BDF_TO_SID_TABLE_N                        0x2000
> > >
> > > @@ -117,6 +118,10 @@
> > >  /* PARF_LTSSM register fields */
> > >  #define LTSSM_EN                               BIT(8)
> > >
> > > +/* PARF_NO_SNOOP_OVERIDE register fields */
> > > +#define WR_NO_SNOOP_OVERIDE_EN                 BIT(1)
> > > +#define RD_NO_SNOOP_OVERIDE_EN                 BIT(3)
> > > +
> > >  /* PARF_DEVICE_TYPE register fields */
> > >  #define DEVICE_TYPE_RC                         0x4
> > >
> > > @@ -961,6 +966,14 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
> > >
> > >  static int qcom_pcie_post_init_2_7_0(struct qcom_pcie *pcie)
> > >  {
> > > +       struct dw_pcie *pci = pcie->pci;
> > > +       struct device *dev = pci->dev;
> > > +
> > > +       /* Enable cache snooping for SA8775P */
> > > +       if (of_device_is_compatible(dev->of_node, "qcom,pcie-sa8775p"))
> >
> > Quoting my feedback from v1:
> >
> > Obviously: please populate a flag in the data structures instead of
> > doing of_device_is_compatible(). Same applies to the patch 2.
> 
> Mani, I saw your response for the v1, but I forgot to respond. In my
> opinion, it's better to have the flag now, even if it is just for a
> single platform. It allows us to follow the logic of the driver and
> saves few string ops.
> 

Ok, I do not have a strong opinion on this.

- Mani

> >
> >
> > > +               writel(WR_NO_SNOOP_OVERIDE_EN | RD_NO_SNOOP_OVERIDE_EN,
> > > +                               pcie->parf + PCIE_PARF_NO_SNOOP_OVERIDE);
> > > +
> > >         qcom_pcie_clear_hpc(pcie->pci);
> > >
> > >         return 0;
> > > --
> > > 2.7.4
> > >
> >
> >
> > --
> > With best wishes
> > Dmitry
> 
> 
> 
> -- 
> With best wishes
> Dmitry

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