Re: [PATCH 3/3] PCI: imx: Add support for i.MX8MQ

[Andrey Smirnov <andrew.smirnov@gmail.com>]

On Tue, Nov 27, 2018 at 2:46 AM Leonard Crestez <leonard.crestez@nxp.com> wrote:
>
> On 11/27/18 12:06 PM, Lucas Stach wrote:
> > Hi Andrey,
> >
> > Am Montag, den 26.11.2018, 10:24 -0800 schrieb Andrey Smirnov:
> >> On Tue, Nov 20, 2018 at 2:49 AM Leonard Crestez <leonard.crestez@nxp.com> wrote:
> >>>
> >>> On Sat, 2018-11-17 at 10:12 -0800, Andrey Smirnov wrote:
> >>>> @@ -921,7 +1004,28 @@ static int imx6_pcie_probe(struct platform_device *pdev)
> >>>> -     case IMX7D:
> >>>> +     case IMX8MQ:
> >>>> +             if (of_property_read_u32(node, "fsl,iomux-gpr1x",
> >>>> +                                      &imx6_pcie->gpr1x)) {
> >>>> +                     dev_err(dev, "Failed to get GPR1x address\n");
> >>>> +                     return -EINVAL;
> >>>> +             }
> >>>
> >>> This is for distinguishing multiple controllers on the SOC but other
> >>> registers and bits might differ. Isn't it preferable to have a property
> >>> for controller id instead of adding many registers to DT?
> >>
> >> I liked encoding necessary info in DT directly slightly better than
> >> encoding abstract ID and then decoding it further in the driver code.
> >> OTOH, I am not really attached to that path. Lucas, can you comment on
> >> this please?
> >
> > Yes, after rereading the patch with this in mind I agree that having
> > the GPR offset on DT directly is IMO the better approach than an
> > abstract ID.
>
> But it's not a single offset, for example the device_type (EP/RC) has
> bits for the two controllers side-by-side in GPR12.
>

Playing devil's advocate for a bit:

More specifically, currently the following per-controller bits need to
be configured:

- Location of the "device type" field within GPR12
- GPR register to use to control PCIn_CLKREQ_B_OVERRIDE_EN and
PCIn_CLKREQ_B_OVERRIDE_EN (GPR14 vs GPR16)
- Now that Philip spoke against PCIE_CTRL_APPS_CLK_REQ being exposed
via reset controller driver, we need to know which SRC register to use
to control that bit (SRC_PCIEPHY_RCR vs. SRC_PCIE2_RCR)

Thanks,
Andrey Smirnov