linux-kernel - Re: [PATCH 14/15] PCI: brcmstb: Set bus max burst side by chip type

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Date:   Wed, 20 May 2020 10:27:17 -0400
From:   Jim Quinlan <james.quinlan@...adcom.com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" 
        <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/15] PCI: brcmstb: Set bus max burst side by chip type

On Wed, May 20, 2020 at 9:44 AM Nicolas Saenz Julienne
<nsaenzjulienne@...e.de> wrote:
>
> On Tue, 2020-05-19 at 16:34 -0400, Jim Quinlan wrote:
> > From: Jim Quinlan <jquinlan@...adcom.com>
> >
> > The proper value of the parameter SCB_MAX_BURST_SIZE varies
> > per chip.  The 2711 family requires 128B whereas other devices
> > can employ 512.  The assignment is complicated by the fact
> > that the values for this two-bit field have different meanings;
> >
> >   Value   Type_Generic    Type_7278
> >
> >      00       Reserved         128B
> >      01           128B         256B
> >      10           256B         512B
> >      11           512B     Reserved
> >
> > Signed-off-by: Jim Quinlan <jquinlan@...adcom.com>
> > ---
> >  drivers/pci/controller/pcie-brcmstb.c | 18 +++++++++++++++---
> >  1 file changed, 15 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/controller/pcie-brcmstb.c
> > b/drivers/pci/controller/pcie-brcmstb.c
> > index 7bf945efd71b..0dfa1bbd9764 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -53,7 +53,7 @@
> >  #define  PCIE_MISC_MISC_CTRL_SCB_ACCESS_EN_MASK              0x1000
> >  #define  PCIE_MISC_MISC_CTRL_CFG_READ_UR_MODE_MASK   0x2000
> >  #define  PCIE_MISC_MISC_CTRL_MAX_BURST_SIZE_MASK     0x300000
> > -#define  PCIE_MISC_MISC_CTRL_MAX_BURST_SIZE_128              0x0
> > +
> >  #define  PCIE_MISC_MISC_CTRL_SCB0_SIZE_MASK          0xf8000000
> >  #define  PCIE_MISC_MISC_CTRL_SCB1_SIZE_MASK          0x07c00000
> >  #define  PCIE_MISC_MISC_CTRL_SCB2_SIZE_MASK          0x0000001f
> > @@ -276,6 +276,7 @@ struct brcm_pcie {
> >       int                     num_memc;
> >       u64                     memc_size[PCIE_BRCM_MAX_MEMC];
> >       u32                     hw_rev;
> > +     const struct of_device_id *of_id;
> >  };
> >
> >  /*
> > @@ -841,7 +842,7 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> >       int num_out_wins = 0;
> >       u16 nlw, cls, lnksta;
> >       int i, ret, memc;
> > -     u32 tmp, aspm_support;
> > +     u32 tmp, burst, aspm_support;
> >
> >       /* Reset the bridge */
> >       brcm_pcie_bridge_sw_init_set(pcie, 1);
> > @@ -857,10 +858,20 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> >       /* Wait for SerDes to be stable */
> >       usleep_range(100, 200);
> >
> > +     /*
> > +      * SCB_MAX_BURST_SIZE is a two bit field.  For GENERIC chips it
> > +      * is encoded as 0=128, 1=256, 2=512, 3=Rsvd, for BCM7278 it
> > +      * is encoded as 0=Rsvd, 1=128, 2=256, 3=512.
> > +      */
> > +     if (strcmp(pcie->of_id->compatible, "brcm,bcm2711-pcie") == 0)
>
> Would it make sense to use pcie->type here? I know GENERIC != BCM2711, but we
> could define it and avoid adding redundant info in struct brcm_pcie.
Yes, that would get rid of the need for keeping of_id around.

Thanks,
Jim
>
> Regards,
> Nicolas
>
> > +             burst = 0x0; /* 128B */
> > +     else
> > +             burst = (pcie->type == BCM7278) ? 0x3 : 0x2; /* 512 bytes */
> > +
> >       /* Set SCB_MAX_BURST_SIZE, CFG_READ_UR_MODE, SCB_ACCESS_EN */
> >       u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_SCB_ACCESS_EN_MASK);
> >       u32p_replace_bits(&tmp, 1, PCIE_MISC_MISC_CTRL_CFG_READ_UR_MODE_MASK);
> > -     u32p_replace_bits(&tmp, PCIE_MISC_MISC_CTRL_MAX_BURST_SIZE_128,
> > +     u32p_replace_bits(&tmp, burst,
> >                         PCIE_MISC_MISC_CTRL_MAX_BURST_SIZE_MASK);
> >       writel(tmp, base + PCIE_MISC_MISC_CTRL);
> >
> > @@ -1200,6 +1211,7 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> >       pcie->reg_offsets = data->offsets;
> >       pcie->reg_field_info = data->reg_field_info;
> >       pcie->type = data->type;
> > +     pcie->of_id = of_id;
> >
> >       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >       pcie->base = devm_ioremap_resource(&pdev->dev, res);
>