Re: [PATCH] PCI: designware: comment the condition of programming ATU in host init

From: Bjorn Helgaas
Date: Thu Feb 04 2016 - 15:38:03 EST


On Thu, Jan 07, 2016 at 02:12:38PM +0800, Jisheng Zhang wrote:
> Some platforms don't support ATU, e.g pci-keystone.c, these platforms
> use their own address translation component rather than ATU, and they
> provide the rd_other_conf and wr_other_conf to programming the
> translation component then do the required access, so we ignore the ATU
> programming for these platforms. Add the comment to explain the reason.
>
> As Bjorn pointed out,
>
> "these definitions:
>
> #define PCIE_ATU_TYPE_MEM
> #define PCIE_ATU_TYPE_IO
> #define PCIE_ATU_TYPE_CFG0
> #define PCIE_ATU_TYPE_CFG1
>
> and these uses:
>
> - In dw_pcie_host_init(), set PCIE_ATU_TYPE_MEM for unit 1
> (but only if rd_other_conf is not overridden)
>
> - In dw_pcie_rd_other_conf() and dw_pcie_wr_other_conf(),
> set PCIE_ATU_TYPE_CFG0 before config access to own bus;
> set PCIE_ATU_TYPE_CFG1 before config access to other bus;
> set PCIE_ATU_TYPE_IO after completion
>
> Why is that initialization related to rd_other_conf? Shouldn't that
> be set up always? A comment here would be nice..."
>
> To be honest, I can't answer this question immediately until I read the
> code carefully again. So indeed, the comment is really necessary.
>
> Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxxx>

Applied to pci/host-designware for v4.6, thanks, Jisheng!

> ---
> drivers/pci/host/pcie-designware.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/pci/host/pcie-designware.c b/drivers/pci/host/pcie-designware.c
> index 02a7452..b795b20 100644
> --- a/drivers/pci/host/pcie-designware.c
> +++ b/drivers/pci/host/pcie-designware.c
> @@ -517,6 +517,12 @@ int dw_pcie_host_init(struct pcie_port *pp)
> if (pp->ops->host_init)
> pp->ops->host_init(pp);
>
> + /*
> + * If the platform provides ->rd_other_conf, it means the platform
> + * doesn't support ATU, it uses its own address translation component
> + * rather than ATU, so we should ignore ATU programming for this
> + * kind of platform.
> + */
> if (!pp->ops->rd_other_conf)
> dw_pcie_prog_outbound_atu(pp, PCIE_ATU_REGION_INDEX1,
> PCIE_ATU_TYPE_MEM, pp->mem_base,
> --
> 2.7.0.rc3
>
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