[U-Boot] [PATCH 14/15] RFC: x86: minnowmax: Add interrupt routing setup

[Bin Meng]

Hi Simon,

On Wed, Jul 29, 2015 at 9:08 AM, Bin Meng <bmeng.cn at gmail.com> wrote:
> Hi Simon,
>
> On Wed, Jul 29, 2015 at 8:48 AM, Simon Glass <sjg at chromium.org> wrote:
>> Hi Bin,
>>
>> On 28 July 2015 at 18:46, Bin Meng <bmeng.cn at gmail.com> wrote:
>>> Hi Simon,
>>>
>>> On Wed, Jul 29, 2015 at 8:42 AM, Simon Glass <sjg at chromium.org> wrote:
>>>> Hi Bin,
>>>>
>>>> On 28 July 2015 at 18:40, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>> Hi Simon,
>>>>>
>>>>> On Tue, Jul 28, 2015 at 7:58 PM, Simon Glass <sjg at chromium.org> wrote:
>>>>>> Hi Bin,
>>>>>>
>>>>>> On 28 July 2015 at 01:50, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>>>>
>>>>>>> Hi Simon,
>>>>>>>
>>>>>>> On Tue, Jul 28, 2015 at 5:47 AM, Simon Glass <sjg at chromium.org> wrote:
>>>>>>> > At present minnowmax does not correct set up PCI interrupts. This should be
>>>>>>> > done in U-Boot so that devices work correctly in Linux.
>>>>>>> >
>>>>>>> > Note: This code needs to make use of the recent pirq_routing work. It does
>>>>>>> > not seem to support all the required features, so this RFC will hopefully
>>>>>>>
>>>>>>> What features are missing in the existing PIRQ codes? When I did the
>>>>>>> PIRQ support, I checked both TunnelCreek and BayTrail chipset
>>>>>>> datasheet, and found the only difference seems to be the pci
>>>>>>> configuration space vs. memory-mapped IBASE where the pci irq routing
>>>>>>> registers reside.
>>>>>>
>>>>>> I see that each PCI device can be assigned four routes, making up a
>>>>>> 16-bit register. But the code I see in pirq_assign_req() only assigns
>>>>>> a single one, using a byte register.
>>>>>>
>>>>>
>>>>> No, the pci irq routing register is still a 8-bit register on
>>>>> BayTrail, where pirq_assign_irq() programs. The 16-bit register you
>>>>> mentioned should be done in the platform codes. See
>>>>> arch/x86/cpu/queensbay/tnc.c::cpu_irq_init(). By the way actually we
>>>>> can leave those register programmed as they have the optimized default
>>>>> values for all pci devices after power up, unless we intentionally
>>>>> want to change them.
>>>>
>>>> What do you mean by 'leave those register programmed'?
>>>>
>>>
>>> I mean their default value is normally OK, like INTA maps PIRQA, INTB
>>> maps PIRQB, INTC maps PIRQC and INTD maps PIRQD.
>>
>> OK, so drop writing to the pirq registers?
>
> You might need check if BayTrail FSP does any programming on these
> registers. On Intel Crown Bay, I checked those values are the same
> values as documented in the TunnelCreek datasheet.
>
>> Should I program the 16-bit registers? If so, I will need to extend
>> the device tree binding, won't I?
>
> When I did the device tree binding changes, I did not convert these
> registers to use device tree, because their offsets, not like the
> routing registers as programmed in pirq_assign_irq(), is really
> platform specific thing and does not seem to have a good formula to
> calculate its offset (it varies from platform to platform). I
> previously wanted to create some device bindings like below, but I
> think they are really ugly so I did not go that way:
>
> irq-router at 1f,0 {
>     reg = <0x0000f800 0 0 0 0>;
>     compatible = "intel,irq-router";
> ......
>     dev0-intx-offset = <0x2040>;
>     dev0-intx-value = <PIRQA PIRQB PIRQC PIRQD>;
>     dev2-intx-offset = <0x2048>;
>     dev2-intx-value = <PIRQA PIRQB PIRQC PIRQD>;
>     dev4-intx-offset = <0x2060>;
>     dev4-intx-value = <PIRQA PIRQB PIRQC PIRQD>;
>     dev26-intx-offset = <0x20a0>;
>     dev26-intx-value = <PIRQA PIRQB PIRQC PIRQD>;
>     dev31-intx-offset = <0x20c0>;
>     dev31-intx-value = <PIRQA PIRQB PIRQC PIRQD>;
> ......
>
> Sorry I cannot find a better way to describe this in device tree, so I
> chose to implement directly in the cpu_irq_init() to program these
> registers.
>
>>
>> Sorry my understanding is limited on this - and I'd like to use your
>> generic code if possible.
>>
>
> Yes, let's try to use the existing codes. If needed, we can have some
> patches to support new platforms.
>

I just managed to get a BayTrail board (not MinnowMax) and will try to
first port U-Boot (assume it won't take much time) then see how PIRQ
looks like on this platform.

Regards,
Bin