Hi Bjorn,
> From: Bjorn Helgaas, Sent: Saturday, April 15, 2023 4:43 AM
>
> On Fri, Apr 14, 2023 at 03:16:14PM +0900, Yoshihiro Shimoda wrote:
> > Add support for triggering legacy IRQs by using outbound iATU.
> > Outbound iATU is utilized to send assert and de-assert INTx TLPs.
> > The message is generated based on the payloadless Msg TLP with type
> > 0x14, where 0x4 is the routing code implying the terminated at
> > Receiver message. The message code is specified as b1000xx for
> > the INTx assertion and b1001xx for the INTx de-assertion.
>
> s/terminated at Receiver/Terminate at Receiver/, since I assume this
> refers to the Message Routing mechanisms in Table 2-20 in sec 2.2.8.
I'll revise the description on v13.
> I have a slight preference for using "INTx" instead of "legacy IRQ" in
> subject, commit log, function names, etc because it's more specific.
> "Legacy" is clear now, but tends to become obscure over time as more
> and more features are added. Eventually it just means "something old
> that we don't like anymore."
I got it. I'll use "INTx" instead of "legacy" on v13.
> > +static int __dw_pcie_ep_raise_legacy_irq(struct dw_pcie_ep *ep, u8 func_no,
> > + int intx)
> > +{
> > + int ret;
> > +
> > + ret = dw_pcie_ep_send_msg(ep, func_no, PCI_CODE_ASSERT_INTA + intx,
> > + PCI_MSG_ROUTING_LOCAL);
> > + if (ret)
> > + return ret;
> > +
> > + usleep_range(1000, 2000);
>
> Where do these values (1000, 2000) come from? Spec reference would be
> good if there is one.
I referred the values from drivers/pci/controller/pcie-rcar-ep.c, but modified
the second value:
usleep_range(1000, 1001);
Today I checked the documents of PCIe and this controller, but I could not
find any specification about the period. So, I tried some cases a little.
No sleep: Always "NOT OKAY"
udelay(10): Sometimes "NOT OKAY"
usleep_range(50, 100): Always "OKAY"
usleep_range(100, 200): Always "OKAY"
usleep_range(1000, 2000): Always "OKAY"
So, using (1000, 2000) seems too long. So, I'll change the values
as (50, 100) and add comment like below:
/*
* The documents of PCIe and the controller don't mention
* how long the INTx should be asserted. If 10 usec, sometimes
* it failed. So, asserted for 50 usec.
*/
usleep_range(50, 100);
Best regards,
Yoshihiro Shimoda
> Bjorn
