Re: [PATCH v2 3/3] dwc: PCI: intel: Intel PCIe RC controller driver

From: Dilip Kota
Date: Tue Aug 27 2019 - 04:47:39 EST

Hi Martin,

On 8/27/2019 11:09 AM, Chuan Hua, Lei wrote:

now I am wondering:
- if we don't have to disable the interrupt line (once it is enabled),
why can't we enable all of these interrupts at initialization time
(instead of doing it on-demand)?
Good point! we even can remote map_irq patch, directly call

of_irq_parse_and_map_pci as other drivers do.

Irrespective of disabling, imo interrupts(A/B/C/D) should be enabled when they are requested; which happens during map_irq() call.

- if the interrupts do have to be disabled again (that is what I
assumed so far) then where is this supposed to happen? (my solution
for this was to implement a simple interrupt controller within the
PCIe driver which only supports enable/disable. disclaimer: I didn't
ask the PCI or interrupt maintainers for feedback on this yet)


We can implement one interrupt controller, but personally, it has too

much overhead. If we follow this way, almost all modules of all old

lantiq SoCs can implement one interrupt controller. Maybe you can check

with PCI maintainer for their comments.

This is needed. In the old driver, we fixed this by fixup. The original
comment as follows,

ÂÂ * The root complex has a hardwired class of PCI_CLASS_NETWORK_OTHER or
ÂÂ * PCI_CLASS_BRIDGE_HOST, when it is operating as a root complex this
ÂÂ * needs to be switched to * PCI_CLASS_BRIDGE_PCI
ÂÂ */
that would be a good comment to add if you really need it
can you please look at dw_pcie_setup_rc (from pcie-designware-host.c), it does:
ÂÂ /* Enable write permission for the DBI read-only register */
ÂÂ dw_pcie_dbi_ro_wr_en(pci);
ÂÂ /* Program correct class for RC */
ÂÂ dw_pcie_wr_own_conf(pp, PCI_CLASS_DEVICE, 2, PCI_CLASS_BRIDGE_PCI);
ÂÂ /* Better disable write permission right after the update */
ÂÂ dw_pcie_dbi_ro_wr_dis(pci);

so my understanding is that there is a functional requirement to set
however, that requirement is already covered by pcie-designware-host.c
I will task Dilip to check if we can use dwc one.
dw_pcie_setup_rc () cannot be called here because, it is not doing PCI_CLASS_BRIDGE_PCI set alone, it is configuring many other things.