A question on endpoint_test code in the linux source by Kishon Vijay Abraham I.

A question on endpoint_test code in the linux source by Kishon Vijay Abraham I.

[Chan Kim]

Hello linux experts,

I was analyzing drivers/misc/pci_endpoint_test.c (linux-5.15.68)
It uses a miscdev and when the driver receives PCITEST_WRITE command using
ioctl(line 726 in the link below) from the user, the driver sets registers
of the endpoint device and writes COMMAND_READ at register
PCI_ENDPOINT_TEST_COMMAND
(https://elixir.bootlin.com/linux/v5.15.68/source/drivers/misc/pci_endpoint_
test.c#L553 ). This seems to be setting DMA paramaters (source DMA address
and size) and triggering DMA. The driver then waits for completion and I can
see the interrupt service routine completes the
completion(test->irq_raised). I guess the endpoint device should actually do
the DMA-read (when told to use DMA) or read the data to itself(I don't know
where it is) and send interrupt to the host(using msix or msi or intx).

The code was written by "Kishon Vijay Abraham I" and I know it is supposed
to be run with drivers/pci/endpoint/functions/pci-epf-test.c
(https://elixir.bootlin.com/linux/v5.15.68/source/drivers/pci/endpoint/funct
ions/pci-epf-test.c)  in the endpoint side. And how to use this endpoint
framework test is shown in
https://docs.kernel.org/PCI/endpoint/pci-test-howto.html . But I cannot find
where the actual DMA and sending interrupt is occurring in the endpoint side
source code when the registers at set. Am I supposed to be running this code
with some real hardware?(as listed in the pci_device_id in the hostside
pci_endpoint_test.c driver?) Where can I find the corresponding (acting on
the register triggering above) action in the endpoint side?

If you have once seen these codes and send me any hint or suggestion, I'll
be grateful.
Thank you.

Best regards,
Chan Kim





_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

RE: A question on endpoint_test code in the linux source by Kishon Vijay Abraham I.

[Chan Kim]

Oh, I right after I sent my previous email, I realized how it's working.
The endpoint test driver (drivers/pci/endpoint/functions/pci-epf-test.c)
queues delayed work after linkup or binding (binding epc and epf), or after
processing the delayed work (re-queues). And in the delayed work performs
the function "pci_epf_test_cmd_handler" and there it reads the command
register and performs various actions including DMA read for the 'write test
from the RC' that I mentioned in my previous email. After it performs the
command, it sends interrupt to the host using rais_irq function. I had
analyzed this pci-epf-test.c before and right after sending my question I
realized how it's working after searching 'raise_irq' in the endpoint test
code.

Thank you.
Best regards,

Chan Kim

>-----Original Message-----
>From: Chan Kim <ckim@etri.re.kr>
>Sent: Thursday, September 14, 2023 2:39 PM
>To: kernelnewbies@kernelnewbies.org
>Subject: A question on endpoint_test code in the linux source by Kishon
>Vijay Abraham I.
>
>Hello linux experts,
>
>I was analyzing drivers/misc/pci_endpoint_test.c (linux-5.15.68) It uses a
>miscdev and when the driver receives PCITEST_WRITE command using ioctl(line
>726 in the link below) from the user, the driver sets registers of the
>endpoint device and writes COMMAND_READ at register
>PCI_ENDPOINT_TEST_COMMAND
>(https://elixir.bootlin.com/linux/v5.15.68/source/drivers/misc/pci_endpoin
>t_
>test.c#L553 ). This seems to be setting DMA paramaters (source DMA address
>and size) and triggering DMA. The driver then waits for completion and I
can
>see the interrupt service routine completes the
completion(test->irq_raised).
>I guess the endpoint device should actually do the DMA-read (when told to
>use DMA) or read the data to itself(I don't know where it is) and send
>interrupt to the host(using msix or msi or intx).
>
>The code was written by "Kishon Vijay Abraham I" and I know it is supposed
>to be run with drivers/pci/endpoint/functions/pci-epf-test.c
>(https://elixir.bootlin.com/linux/v5.15.68/source/drivers/pci/endpoint/fun
>ct
>ions/pci-epf-test.c)  in the endpoint side. And how to use this endpoint
>framework test is shown in https://docs.kernel.org/PCI/endpoint/pci-test-
>howto.html . But I cannot find where the actual DMA and sending interrupt
is
>occurring in the endpoint side source code when the registers at set. Am I
>supposed to be running this code with some real hardware?(as listed in the
>pci_device_id in the hostside pci_endpoint_test.c driver?) Where can I find
>the corresponding (acting on the register triggering above) action in the
>endpoint side?
>
>If you have once seen these codes and send me any hint or suggestion, I'll
>be grateful.
>Thank you.
>
>Best regards,
>Chan Kim
>
>
>
>
>
>_______________________________________________
>Kernelnewbies mailing list
>Kernelnewbies@kernelnewbies.org
>https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies





_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies