linux-kernel - Re: [PATCH] PCI: tegra: Use PCI_CONF1_EXT

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Date:   Tue, 11 Oct 2022 16:42:34 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Pali Rohár <pali@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Vidya Sagar <vidyas@...dia.com>
Cc:     linux-tegra@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: tegra: Use PCI_CONF1_EXT_ADDRESS() macro


On 28/09/2022 13:19, Pali Rohár wrote:
> Simplify pci-tegra.c driver code and use new PCI_CONF1_EXT_ADDRESS() macro
> for accessing PCI config space.
> 
> Signed-off-by: Pali Rohár <pali@...nel.org>
> ---
> Please look also at this related patch:
> https://patchwork.kernel.org/project/linux-pci/patch/20220911113216.14892-1-pali@kernel.org/
> ---
>   drivers/pci/controller/pci-tegra.c | 11 +++--------
>   1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
> index 5df90d183526..c9924e75e597 100644
> --- a/drivers/pci/controller/pci-tegra.c
> +++ b/drivers/pci/controller/pci-tegra.c
> @@ -417,13 +417,6 @@ static inline u32 pads_readl(struct tegra_pcie *pcie, unsigned long offset)
>    * address (access to which generates correct config transaction) falls in
>    * this 4 KiB region.
>    */
> -static unsigned int tegra_pcie_conf_offset(u8 bus, unsigned int devfn,
> -					   unsigned int where)
> -{
> -	return ((where & 0xf00) << 16) | (bus << 16) | (PCI_SLOT(devfn) << 11) |
> -	       (PCI_FUNC(devfn) << 8) | (where & 0xff);
> -}
> -
>   static void __iomem *tegra_pcie_map_bus(struct pci_bus *bus,
>   					unsigned int devfn,
>   					int where)
> @@ -445,7 +438,9 @@ static void __iomem *tegra_pcie_map_bus(struct pci_bus *bus,
>   		unsigned int offset;
>   		u32 base;
>   
> -		offset = tegra_pcie_conf_offset(bus->number, devfn, where);
> +		offset = PCI_CONF1_EXT_ADDRESS(bus->number, PCI_SLOT(devfn),
> +					       PCI_FUNC(devfn), where) &
> +			 ~PCI_CONF1_ENABLE;
>   
>   		/* move 4 KiB window to offset within the FPCI region */
>   		base = 0xfe100000 + ((offset & ~(SZ_4K - 1)) >> 8);


Our PCIe test on Tegra124 Jetson TK1 is currently failing on -next and 
bisect points to this commit. Looking at bit closer, the problem appears 
to be the PCI_CONF1_REG_MASK which has a value of 0xfc. Before this 
patch was applied a mask of 0xff was applied to the lower 8-bits of 
'where' and now it is 0xfc. So this does not work for Tegra as it is.

Let me know if you have any thoughts?

Jon

-- 
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