AM5728: Slow PCIe access to SSD

Hi Koichiro-san,

I am not sure what causes this, but please first let me try to reproduce the issue on my evm. It might take a little longer, our office is closed due to recent tornado damage, but started the recovery process since this week. I will update as soon as I made progress.

Hi Koichiro-san,

Sorry for the late response. I don't have a MVME PCIe x1 device, so I tested your script with a USB thumb drive on a PCIE-USB card FL1100, with SDK6.0 RT Linux, but I don't see the issue, your script takes about 1 second.

Do you have other PCIe device to test?

Hi,

Customer is using PCIe to M.2 adapter board, like this:
https://images-na.ssl-images-amazon.com/images/I/31MlZfJgETL.jpg

Do you have similar device somewhere in your office?

Thanks and regards,
Koichiro Tashiro

Hi Koichiro,

I don't, but I just ordered a similar adapter card, I should receive it in a couple weeks. I will let you know the test result once I receive it.

Hi Koichiro-san,

I got a M.2 on a PCIe adapter card, and I can reproduce the issue with v4.4 RT and non-RT kernels, but I don't see the issue with v4.19 kernel in the Processor SDK, it took only a second to finish the test. Can you please ask the customer to test with the latest Processor SDK Linux v6.1?

Hi Bin,

Thanks for reproducing the issue on your side.

Unfortunately, customer cannot update Kernel version as this will impact to their product a lot.
Could you provide updated PCIe driver work with Kernel v4.4.41-rt50?

Thanks and regards,
Koichiro Tashiro

Hi Bin,

As I said customer cannot migrate to the latest SDK, so they will try to port PCIe driver from SDK v6.1 to kernel 4.4.
If they see troubles in porting, I will open other thread.

Thanks and regards,
Koichiro Tashiro

Hi Koichiro-san,

Just porting the PCIe driver without knowing the root cause might not be a good idea. The problem might not be in the PCIe driver, it could be in the NVME driver, SCSI driver, or somewhere in the filessystem driver as well.

Porting to a different kernel shouldn't cause more effort then porting PCIe drivers. Anyway, opening a new thread regarding the same issue on kernel 4.4 won't help, as the answer would be the same - kernel 4.4 is no longer supported and the issue is solved in TI v4.19 kernel.