RAM access from PCIe device
by ranshalit from LinuxQuestions.org on (#4VSKD)
Hello,
I have a simple kernel module which allocates continuous physical memory (using dma_alloc_coherent) and provide it to PCIe connected FPGA device for DMA access, 64-bit addressing PCIe.
But on when FPGA tries to access the cpu RAM (using FPGA's dma), it can't access and fails. This is in our lenovo computer.
So, I suspected centos8 and kernel 4.18, but using same OS, kernel, same kernel module, and FPGA works perfectly if I just move them into older computer !
So now, I started suspecting the lenovo machine, but installing windows on same machine, we get that FPGA can do DMA without any issues.
Is there any idea what can cause such strange behavior ?
Thanks
I have a simple kernel module which allocates continuous physical memory (using dma_alloc_coherent) and provide it to PCIe connected FPGA device for DMA access, 64-bit addressing PCIe.
But on when FPGA tries to access the cpu RAM (using FPGA's dma), it can't access and fails. This is in our lenovo computer.
So, I suspected centos8 and kernel 4.18, but using same OS, kernel, same kernel module, and FPGA works perfectly if I just move them into older computer !
So now, I started suspecting the lenovo machine, but installing windows on same machine, we get that FPGA can do DMA without any issues.
Is there any idea what can cause such strange behavior ?
Thanks