linux-kernel - Re: [PATCH] PCI: Mediatek: Use resource

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Date:   Wed, 30 Jan 2019 10:03:29 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     honghui.zhang@...iatek.com
Cc:     lorenzo.pieralisi@....com, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, ryder.lee@...iatek.com,
        youlin.pei@...iatek.com, jianjun.wang@...iatek.com
Subject: Re: [PATCH] PCI: Mediatek: Use resource_size function on resource
 object

On Wed, Jan 02, 2019 at 02:03:53PM +0800, honghui.zhang@...iatek.com wrote:
> From: Honghui Zhang <honghui.zhang@...iatek.com>
> 
> drivers/pci/pcie-mediatek.c:720:13-16: WARNING: Suspicious code. resource_size is maybe missing with mem
> 
> Generated by: scripts/coccinelle/api/resource_size.cocci
> 
> Signed-off-by: Honghui Zhang <honghui.zhang@...iatek.com>
> ---
>  drivers/pci/controller/pcie-mediatek.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
> index e307166..0168376 100644
> --- a/drivers/pci/controller/pcie-mediatek.c
> +++ b/drivers/pci/controller/pcie-mediatek.c
> @@ -654,7 +654,6 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
>  	struct resource *mem = &pcie->mem;
>  	const struct mtk_pcie_soc *soc = port->pcie->soc;
>  	u32 val;
> -	size_t size;
>  	int err;
>  
>  	/* MT7622 platforms need to enable LTSSM and ASPM from PCIe subsys */
> @@ -706,8 +705,7 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
>  		mtk_pcie_enable_msi(port);
>  
>  	/* Set AHB to PCIe translation windows */
> -	size = mem->end - mem->start;
> -	val = lower_32_bits(mem->start) | AHB2PCIE_SIZE(fls(size));
> +	val = lower_32_bits(mem->start) | AHB2PCIE_SIZE(fls(resource_size(mem)));
>  	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
>  
>  	val = upper_32_bits(mem->start);

Unrelated to this patch, but just below this:

        /* Set PCIe to AXI translation memory space.*/
        val = fls(0xffffffff) | WIN_ENABLE;
        writel(val, port->base + PCIE_AXI_WINDOW0);

Can you double-check the use of "fls(0xffffffff)"?  That expression is
a constant and I think evaluates to 31 (0x1f), i.e.,

        val = 0x1f | WIN_ENABLE;

I don't know the hardware, so this might be correct, but
"fls(0xffffffff)" looks funny because I think it's the same as
"fls(0x80000000)".

Bjorn