linux-kernel - Re: [PATCH 8/8] PCI: aardvark: Add FIXME for code which access PCIE_CORE_CMD_STATUS

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Date:   Wed, 15 Apr 2020 18:18:36 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Jason Cooper <jason@...edaemon.net>, Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Remi Pommarel <repk@...plefau.lt>,
        Marek Behún <marek.behun@....cz>,
        Tomasz Maciej Nowak <tmn505@...il.com>,
        Xogium <contact@...ium.me>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH 8/8] PCI: aardvark: Add FIXME for code which access
 PCIE_CORE_CMD_STATUS_REG

On Wednesday 15 April 2020 18:03:48 Pali Rohár wrote:
> Register PCIE_CORE_CMD_STATUS_REG is applicable only when aardvark
> controller is configured for Endpoint mode. Which is not the case of
> current kernel driver.
> 
> Signed-off-by: Pali Rohár <pali@...nel.org>
> ---
>  drivers/pci/controller/pci-aardvark.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> index 6a97a3838098..a1cebc734f2d 100644
> --- a/drivers/pci/controller/pci-aardvark.c
> +++ b/drivers/pci/controller/pci-aardvark.c
> @@ -423,6 +423,12 @@ static void advk_pcie_setup_hw(struct advk_pcie *pcie)
>  		advk_writel(pcie, reg, PCIE_CORE_LINK_CTRL_STAT_REG);
>  	} while (1);
>  
> +	/*
> +	 * FIXME: Following code which access PCIE_CORE_CMD_STATUS_REG register
> +	 *        is suspicious. This register is applicable only when the PCI
> +	 *        controller is configured for Endpoint mode. And not when it
> +	 *        is configured for Root Complex.
> +	 */
>  	reg = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG);
>  	reg |= PCIE_CORE_CMD_MEM_ACCESS_EN |
>  		PCIE_CORE_CMD_IO_ACCESS_EN |
> -- 
> 2.20.1
> 

Just to note, above code needs to be removed or fixed or properly
commented why is correct and what is doing.

I really do not know, so I'm adding at least FIXME comment to document
suspicious code which may cause unexpected problems.