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SubjectRe: [PATCH v2 9/9] PCI: rockchip: Add parameter check for RK3399 PCIe endpoint core set_msi()
On Tue, Feb 21, 2023 at 2:19 PM Rick Wertenbroek
<rick.wertenbroek@gmail.com> wrote:
>
> On Tue, Feb 21, 2023 at 11:55 AM Damien Le Moal
> <damien.lemoal@opensource.wdc.com> wrote:
> >
> > On 2/21/23 19:47, Rick Wertenbroek wrote:
> > > On Wed, Feb 15, 2023 at 2:39 AM Damien Le Moal
> > > <damien.lemoal@opensource.wdc.com> wrote:
> > >>
> > >> On 2/14/23 23:08, Rick Wertenbroek wrote:
> > >>> The RK3399 PCIe endpoint core supports only a single PCIe physcial
> > >>> function (function number 0), therefore return -EINVAL if set_msi() is
> > >>> called with a function number greater than 0.
> > >>> The PCIe standard only allows the multi message capability (MMC) value
> > >>> to be up to 0x5 (32 messages), therefore return -EINVAL if set_msi() is
> > >>> called with a MMC value of over 0x5.
> > >>>
> > >>> Signed-off-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
> > >>> ---
> > >>> drivers/pci/controller/pcie-rockchip-ep.c | 10 ++++++++++
> > >>> 1 file changed, 10 insertions(+)
> > >>>
> > >>> diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
> > >>> index b7865a94e..80634b690 100644
> > >>> --- a/drivers/pci/controller/pcie-rockchip-ep.c
> > >>> +++ b/drivers/pci/controller/pcie-rockchip-ep.c
> > >>> @@ -294,6 +294,16 @@ static int rockchip_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn,
> > >>> struct rockchip_pcie *rockchip = &ep->rockchip;
> > >>> u32 flags;
> > >>>
> > >>> + if (fn) {
> > >>> + dev_err(&epc->dev, "This endpoint controller only supports a single physical function\n");
> > >>> + return -EINVAL;
> > >>> + }
> > >>
> > >> Checking this here is late... Given that at most only one physical
> > >> function is supported, the check should be in rockchip_pcie_parse_ep_dt().
> > >> Something like:
> > >>
> > >> err = of_property_read_u8(dev->of_node, "max-functions",
> > >> &ep->epc->max_functions);
> > >>
> > >> if (err < 0 || ep->epc->max_functions > 1)
> > >>
> > >> ep->epc->max_functions = 1;
> > >>
> > >
> > > Yes, this could be moved to the probe, thanks.
> > >
> > >> And all the macros with the (fn) argument could also be simplified
> > >> (argument fn removed) since fn will always be 0.
> > >
> > > These functions cannot be simplified because they have to follow the signature
> > > given by "pci_epc_ops" (include/linux/pci-epc.h). And this signature has the
> > > function number as a parameter. If we change the function signature we won't
> > > be able to assign these functions to the pc_epc_ops structure
> >
> > I was not suggesting to change the functions signature. I was suggesting
> > dropping the fn argument for the *macros*, e.g.
> >
> > ROCKCHIP_PCIE_EP_FUNC_BASE(fn) -> ROCKCHIP_PCIE_EP_FUNC_BASE
> >
> > since fn is always 0.
> >
> > That said, I am not entirely sure if the limit really is 1 function at most. The
> > TRM seems to be suggesting that up to 4 functions can be supported...
> >
> > [...]
> >
> > >> Another nice cleanup: define ROCKCHIP_PCIE_EP_MSI_CTRL_REG to include the
> > >> ROCKCHIP_PCIE_EP_FUNC_BASE(fn) addition so that we do not have to do it
> > >> here all the time.
> > >
> > > Yes, this could be an improvement but this is the way it is written
> > > everywhere in this
> > > driver, I chose to keep it so as to remain coherent with the rest of the driver.
> > > Cleaning this is not so important since this code will not be
> > > rewritten / changed so
> > > often. But I agree that it might be nicer. But, on the other side if
> > > at some point
> > > support for virtual functions would be added, the offsets would need
> > > to be computed
> > > based on the virtual function number and the code would be written
> > > like it is now,
> > > so I suggest keeping this the way it is for now.
> >
> > Yes, sure, this can be cleaned later.
> >
> > A more pressing problem is the lack of support for MSIX despite the fact that
> > the controller supports that *and* advertize it as a capability. That is what
> > was causing my problem with the Linux nvme driver and my prototype nvme epf
> > function driver: the host driver was seeing MSIX support (1 vector supported by
> > default), and so was allocating one MSIX for the device probe. But on the EP
> > end, it is MSI or INTX only... Working on adding that to solve this issue.
> >
>
> I have seen this too, the controller advertises the capability. However, the TRM
> (section 17.5.9) says that MSI-X is not supported (MSI / INTx only as you said).
> So the solution should be to modify the probe function of the endpoint
> controller
> so that the MSI-X capability would not be advertised, this should fix
> your problem.
>
> I wonder if one could still implement MSI-X because from the endpoint we would
> just need to implement it as a message (TLP) over PCIe (because the space for
> the vectors is allocated and written, so that part should be ok). I am
> not an expert
> on MSI-X, but the reason the endpoint cannot send them could be because MSI-X
> requires some fields in the PCIe header descriptor to be filled with values that
> cannot be set through the "desc0-3" registers of the RK3399 PCIe endpoint core.
>
> Anyways, the endpoint should not advertise the MSI-X capabilities when it cannot
> send such interrupts. Once this is fixed you should be able to have your NVMe
> function running.
>
> Regards.
> Rick
>

It is possible to disable MSI-X by skipping the MSI-X capability
structure in the PCIe
capabilities structures linked-list.
The current linked list is MSI cap (0x90) -> MSI-X cap (0xb0) -> PCIe
Device cap (0xc0)
So we want to set MSI (0x90) -> PCIe Device cap (0xc0)

This can be done by writing 0xc0 to bits 15-8 of 0xFDA0'0090 (MSI cap).
I tested this quickly through devmem2 before loading the endpoint
function driver
and it fixes the issue of MSI-X capabilities being advertised to the host.

In the driver the changes would look like this;
In the probe function you can disable MSI-X as follows:

@@ -631,6 +618,28 @@ static int rockchip_pcie_ep_probe(struct
platform_device *pdev)

ep->irq_pci_addr = ROCKCHIP_PCIE_EP_DUMMY_IRQ_ADDR;

+ /*
+ * Disable MSI-X because the controller is not capable of MSI-X
+ * This requires to skip the MSI-X capabilities entry in the
+ * chain of PCIe capabilities, we get the next pointer from the
+ * MSI-X entry and set that in the MSI capability entry, this way
+ * the MSI-X entry is skipped (left out of the linked-list)
+ */
+ cfg_msi = rockchip_pcie_read(rockchip, PCIE_EP_CONFIG_BASE +
+ ROCKCHIP_PCIE_EP_MSI_CTRL_REG);
+
+ cfg_msi &= ~ROCKCHIP_PCIE_EP_MSI_CP1_MASK;
+
+ cfg_msix_cp = rockchip_pcie_read(rockchip, PCIE_EP_CONFIG_BASE +
+ ROCKCHIP_PCIE_EP_MSIX_CAP_REG) &
ROCKCHIP_PCIE_EP_MSIX_CAP_CP_MASK;
+
+ cfg_msi |= cfg_msix_cp;
+
+ rockchip_pcie_write(rockchip, cfg_msi,
+ PCIE_EP_CONFIG_BASE + ROCKCHIP_PCIE_EP_MSI_CTRL_REG);
+
rockchip_pcie_write(rockchip, PCIE_CLIENT_CONF_ENABLE,
PCIE_CLIENT_CONFIG);

return 0;
err_epc_mem_exit:
pci_epc_mem_exit(epc);

In the pcie-rockchip.h add the following #defines:

@@ -216,21 +227,28 @@
#define ROCKCHIP_PCIE_EP_CMD_STATUS 0x4
#define ROCKCHIP_PCIE_EP_CMD_STATUS_IS BIT(19)
#define ROCKCHIP_PCIE_EP_MSI_CTRL_REG 0x90
+#define ROCKCHIP_PCIE_EP_MSI_CP1_OFFSET 8
+#define ROCKCHIP_PCIE_EP_MSI_CP1_MASK GENMASK(15, 8)
+#define ROCKCHIP_PCIE_EP_MSI_FLAGS_OFFSET 16
#define ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_OFFSET 17
#define ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_MASK GENMASK(19, 17)
#define ROCKCHIP_PCIE_EP_MSI_CTRL_MME_OFFSET 20
#define ROCKCHIP_PCIE_EP_MSI_CTRL_MME_MASK GENMASK(22, 20)
#define ROCKCHIP_PCIE_EP_MSI_CTRL_ME BIT(16)
#define ROCKCHIP_PCIE_EP_MSI_CTRL_MASK_MSI_CAP BIT(24)
+#define ROCKCHIP_PCIE_EP_MSIX_CAP_REG 0xb0
+#define ROCKCHIP_PCIE_EP_MSIX_CAP_CP_OFFSET 8
+#define ROCKCHIP_PCIE_EP_MSIX_CAP_CP_MASK GENMASK(15, 8)
#define ROCKCHIP_PCIE_EP_DUMMY_IRQ_ADDR 0x1
#define ROCKCHIP_PCIE_EP_PCI_LEGACY_IRQ_ADDR 0x3

I will add this to the next version of the patch set.
Thank you Damien for pointing this out ! This should solve the issues
you have with
your NVMe endpoint function regarding MSI-X interrupts.

Regards
Rick

>
> > --
> > Damien Le Moal
> > Western Digital Research
> >

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