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SubjectRe: [PATCH v2 1/2] PCI: mediatek: Use resource_size function on resource object
On Thu, Jan 31, 2019 at 04:01:52PM +0800, honghui.zhang@mediatek.com wrote:
> From: Honghui Zhang <honghui.zhang@mediatek.com>
>
> scripts/coccinelle/api/resource_size.cocci complain about the
> following warning:
>
> pcie-mediatek.c:720:13-16: WARNING: Suspicious code. resource_size is maybe missing with mem
>
> Use resource_size(mem) instead of mem->end - mem->start to eliminate the
> complain. Since the MMIO window size for both MT2712 and MT7622 are all
> 0x1000_0000, this change also fix the AHB2PCIe window size smaller than
> HW MMIO window size issue by change the values of fls(size) from
> fls(0xfff_ffff) to fls(0x1000_0000).

Good, I'm glad this actually fixes a bug. The warning was actually
useful!

Since that's the case, the *bug* is the important thing (not the
warning), and the subject line should be about the bug fix. The fact
that it also happens to remove a warning is really just incidental.

You say "the AHB2PCIe window size smaller than HW MMIO window size
issue" as though it should be familiar to us. But it's not :)

So the changelog needs to start by explaining what the AHB2PCIe window
size issue is, mention what user-visible problem that causes, then
explain how you're fixing it by using resource_size().

Then you can mention that this also incidentally removes a coccinelle
warning.

Bjorn

> Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
> ---
> drivers/pci/controller/pcie-mediatek.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
> index 55e471c..01126b8 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 +705,8 @@ 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)));

Nit: I think it's more typical to put the "|" on the first line.

> writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
>
> val = upper_32_bits(mem->start);
> --
> 2.6.4
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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