linux-kernel - Re: [PATCH] PCI: fu740: RFC: force gen1 and get devices probing

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Date:   Fri, 4 Feb 2022 21:12:19 +0200
From:   David Abdurachmanov <david.abdurachmanov@...il.com>
To:     Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Greentime Hu <greentime.hu@...ive.com>,
        lorenzo.pieralisi@....com, robh@...nel.org, kw@...ux.com,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>, macro@...am.me.uk
Subject: Re: [PATCH] PCI: fu740: RFC: force gen1 and get devices probing

On Fri, Feb 4, 2022 at 8:35 PM Ben Dooks <ben.dooks@...ethink.co.uk> wrote:
>
> The dw pcie core does not probe devices unless this fix
> from u-boot is applied. The link must be changed to gen1
> and then the system will see all the other pcie devices
> behind the unmatched board's bridge.
>
> This is a quick PoC to try and get our test farm working
> when a system does not have the pcie initialised by a
> u-boot script.
>
> I will look at a proper patch when I am back in the office

Hi,

Have you looked into the patches posted for Linux and U-Boot from
Maciej W. Rozycki?

On the Linux side (not reviewed yet):
[PATCH v3] pci: Work around ASMedia ASM2824 PCIe link training failures
https://www.spinics.net/lists/linux-pci/msg120112.html

The U-Boot fix was merged a few days ago.

david

> ---
>  drivers/pci/controller/dwc/pcie-fu740.c | 37 +++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-fu740.c b/drivers/pci/controller/dwc/pcie-fu740.c
> index 960e58ead5f2..44f792764e45 100644
> --- a/drivers/pci/controller/dwc/pcie-fu740.c
> +++ b/drivers/pci/controller/dwc/pcie-fu740.c
> @@ -181,11 +181,48 @@ static void fu740_pcie_init_phy(struct fu740_pcie *afp)
>         fu740_phyregwrite(1, PCIEX8MGMT_PHY_LANE3_BASE, PCIEX8MGMT_PHY_INIT_VAL, afp);
>  }
>
> +/* u-boot forces system to gen1 otherwise nothing probes... */
> +static void pcie_sifive_force_gen1(struct dw_pcie *dw, struct fu740_pcie *afp )
> +{
> +       unsigned val;
> +
> +#if 0
> +       /* u-boot code */
> +        /* ctrl_ro_wr_enable */
> +        val = readl(sv->dw.dbi_base + PCIE_MISC_CONTROL_1);
> +        val |= DBI_RO_WR_EN;
> +        writel(val, sv->dw.dbi_base + PCIE_MISC_CONTROL_1);
> +
> +        /* configure link cap */
> +        linkcap = readl(sv->dw.dbi_base + PF0_PCIE_CAP_LINK_CAP);
> +        linkcap |= PCIE_LINK_CAP_MAX_SPEED_MASK;
> +        writel(linkcap, sv->dw.dbi_base + PF0_PCIE_CAP_LINK_CAP);
> +
> +        /* ctrl_ro_wr_disable */
> +        val &= ~DBI_RO_WR_EN;
> +        writel(val, sv->dw.dbi_base + PCIE_MISC_CONTROL_1);
> +#endif
> +
> +       val = readl_relaxed(dw->dbi_base +  PCIE_MISC_CONTROL_1_OFF);
> +       val |= PCIE_DBI_RO_WR_EN;
> +       writel_relaxed(val, dw->dbi_base +  PCIE_MISC_CONTROL_1_OFF);
> +
> +       val = readl(dw->dbi_base + 0x70 + 0x0c);
> +       val |= 0xf;
> +       writel(val, dw->dbi_base + 0x70 + 0x0c);
> +
> +       val = readl_relaxed(dw->dbi_base +  PCIE_MISC_CONTROL_1_OFF);
> +       val &= ~PCIE_DBI_RO_WR_EN;
> +       writel_relaxed(val, dw->dbi_base +  PCIE_MISC_CONTROL_1_OFF);
> +}
> +
>  static int fu740_pcie_start_link(struct dw_pcie *pci)
>  {
>         struct device *dev = pci->dev;
>         struct fu740_pcie *afp = dev_get_drvdata(dev);
>
> +       pcie_sifive_force_gen1(pci, afp);
> +
>         /* Enable LTSSM */
>         writel_relaxed(0x1, afp->mgmt_base + PCIEX8MGMT_APP_LTSSM_ENABLE);
>         return 0;
> --
> 2.34.1
>
>
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> linux-riscv@...ts.infradead.org
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