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SubjectRe: Possible issue at the kirin-pcie driver
Hi Mauro,

On Tue, Jul 06, 2021 at 11:35:03AM +0200, Mauro Carvalho Chehab wrote:
> Hi,
>
> I was asked by Rob Herring to convert the kiring-pcie driver on two parts,
> splitting the PHY logic from it, in order to be able to add PHY support
> for Hikey 970 at drivers/pci/controller/dwc/pcie-kirin.c.
>
> While doing so, I noticed something weird issue at the driver, with regards
> to a certain register (PCIE_APB_PHY_STATUS0), as shown below:
>
> ...
>
> #define PCIE_APB_PHY_STATUS0 0x400
> ...
> static inline u32 kirin_apb_ctrl_readl(struct kirin_pcie *kirin_pcie, u32 reg)
> {
> return readl(kirin_pcie->apb_base + reg);
> }
> ...
> static inline u32 kirin_apb_phy_readl(struct kirin_pcie *kirin_pcie, u32 reg)
> {
> return readl(kirin_pcie->phy_base + reg);
> }
> ...
> static int kirin_pcie_phy_init(struct kirin_pcie *kirin_pcie)
> {
> ...
> reg_val = kirin_apb_phy_readl(kirin_pcie, PCIE_APB_PHY_STATUS0);
> if (reg_val & PIPE_CLK_STABLE) {
> dev_err(dev, "PIPE clk is not stable\n");
> return -EINVAL;
> }
> }
> ...
> static int kirin_pcie_link_up(struct dw_pcie *pci)
> {
> struct kirin_pcie *kirin_pcie = to_kirin_pcie(pci);
> u32 val = kirin_apb_ctrl_readl(kirin_pcie, PCIE_APB_PHY_STATUS0);
>
> if ((val & PCIE_LINKUP_ENABLE) == PCIE_LINKUP_ENABLE)
> return 1;
>
> return 0;
>
> u32 val = kirin_apb_ctrl_readl(kirin_pcie, PCIE_APB_PHY_STATUS0);
>
> if ((val & PCIE_LINKUP_ENABLE) == PCIE_LINKUP_ENABLE)
> return 1;
>
> Basically, the code at kirin_pcie_phy_init() use this register as if it is
> part of the PHY memory region (0xf3f20000 + 0x400), while the code at
> kirin_pcie_link_up() considers is as belonging to the APB memory
> region (0xff3fe000 + 0x400).
>
> It sounds to me that there's a mistake somewhere. I mean, either:
>
> 1. there is a cut-and-paste error, caused it to access the wrong memory
> region, e.g. at kirin_pcie_link_up() the logic should be:
>
> u32 val = kirin_apb_phy_readl(kirin_pcie, PCIE_APB_PHY_STATUS0);
>
> instead of:
>
> u32 val = kirin_apb_ctrl_readl(kirin_pcie, PCIE_APB_PHY_STATUS0);
>
> (or the reverse)
>
> 2. Both memory regions have a register at address 0x400 with similar
> names that ended being merged into the same macro;
>
> 3. the register for APB PHY status0 is duplicated on both regions and,
> on both, they are at region_base + 0x400.
>

I don't have the datasheet for Kirin970 but...

I think 2 & 3 are the possible ones as I've seen register duplications
across multiple vendors.

> I suspect that it is (1), but, as I don't have any datasheets or
> register map, I can't tell for sure.
>

If it is 1, then I don't think the driver can work reliably.

Anyway, I think you can still move forward with the splitting provided
that you can access this register in both drivers.

Thanks,
Mani

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