linux-kernel - Re: [PATCH v2 9/9] PCI: rockchip: Add parameter check for RK3399 PCIe endpoint core set

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Date:   Wed, 15 Feb 2023 10:39:39 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Rick Wertenbroek <rick.wertenbroek@...il.com>,
        alberto.dassatti@...g-vd.ch
Cc:     xxm@...k-chips.com, rick.wertenbroek@...g-vd.ch,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Mikko Kovanen <mikko.kovanen@...amobile.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v2 9/9] PCI: rockchip: Add parameter check for RK3399 PCIe
 endpoint core set_msi()

On 2/14/23 23:08, Rick Wertenbroek wrote:
> The RK3399 PCIe endpoint core supports only a single PCIe physcial
> function (function number 0), therefore return -EINVAL if set_msi() is
> called with a function number greater than 0.
> The PCIe standard only allows the multi message capability (MMC) value
> to be up to 0x5 (32 messages), therefore return -EINVAL if set_msi() is
> called with a MMC value of over 0x5.
> 
> Signed-off-by: Rick Wertenbroek <rick.wertenbroek@...il.com>
> ---
>  drivers/pci/controller/pcie-rockchip-ep.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
> index b7865a94e..80634b690 100644
> --- a/drivers/pci/controller/pcie-rockchip-ep.c
> +++ b/drivers/pci/controller/pcie-rockchip-ep.c
> @@ -294,6 +294,16 @@ static int rockchip_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn,
>  	struct rockchip_pcie *rockchip = &ep->rockchip;
>  	u32 flags;
>  
> +	if (fn) {
> +		dev_err(&epc->dev, "This endpoint controller only supports a single physical function\n");
> +		return -EINVAL;
> +	}

Checking this here is late... Given that at most only one physical
function is supported, the check should be in rockchip_pcie_parse_ep_dt().
Something like:

	err = of_property_read_u8(dev->of_node, "max-functions",
                                  &ep->epc->max_functions);

        if (err < 0 || ep->epc->max_functions > 1)

                ep->epc->max_functions = 1;

And all the macros with the (fn) argument could also be simplified
(argument fn removed) since fn will always be 0.

> +
> +	if (mmc > 0x5) {
> +		dev_err(&epc->dev, "Number of MSI IRQs cannot be more than 32\n");

Long line. Please split it after the comma.

> +		return -EINVAL;
> +	}
> +
>  	flags = rockchip_pcie_read(rockchip,
>  				   ROCKCHIP_PCIE_EP_FUNC_BASE(fn) +
>  				   ROCKCHIP_PCIE_EP_MSI_CTRL_REG);

Another nice cleanup: define ROCKCHIP_PCIE_EP_MSI_CTRL_REG to include the
ROCKCHIP_PCIE_EP_FUNC_BASE(fn) addition so that we do not have to do it
here all the time.

-- 
Damien Le Moal
Western Digital Research