Re: [coreboot] Wired problems with Intel skylake based board

[Naresh G. Solanki]

Hi,

There are two things here.
1.  System fails to boot i.e., hangs
2.  FPGA's connected to root port are not detected in FW/OS

For problem 1, can you give data on where exactly it hangs?, Is it in
OS or FW ?, Can you provide kernel/coreboot log, port 80 dump when it
hangs.
For problem 2, Can you try setting UPD PcieRpHotPlug, & check the
behaviour. reference:
https://review.coreboot.org/cgit/coreboot.git/tree/src/soc/intel/skylake/chi...

Can you please check FPGA datasheet & check for frequency tolerance of
PCIE_CLK_REF signal from FPGA.
Also can you re-verify board layout for any PDG(Platform Design Guide)
violations like impedance, length matching, limits for  differential
PCIE_CLK_REF, PCIe Lanes.
Sometimes noise generated within board can generate huge EMI. I assume
high noisy circuits(power supply, backlight driver etc) are kept away
from high speed PCIe signals.

Regards,
Naresh G Solanki
On Mon, Oct 15, 2018 at 5:37 PM Christian Gmeiner
 wrote:
> Am Fr., 12. Okt. 2018 um 10:15 Uhr schrieb Nico Huber :
> > On 10/11/18 11:29 AM, Christian Gmeiner wrote:
> > > During the last weeks I found the root cause of my problem - PCIe
> > > spread spectrum
> > >
> > > Our FPGAs need a stable 100MHz PCIE clock to work. The used FSP config
> > > thing looked
> > > like this:
> > >
> > > void mainboard_memory_init_params(FSPM_UPD *mupd)
> > > {
> > >     FSP_M_CONFIG *mem_cfg;
> > >     struct spd_block blk = {
> > >         .addr_map = { 0x50 },
> > >     };
> > > mem_cfg = &mupd->FspmConfig;
> > >
> > > mem_cfg->PegDisableSpreadSpectrumClocking = 1;
> > > mem_cfg->PchPmPciePllSsc = 0;
> > >
> > > ...
> > >
> > > }
> > >
> > > With this configuration the PCIe reference clock was off more then 8% which
> > > caused the system to hang during cold and warm boots.
> > >
> > > In the next step I removed assignment of PchPmPciePllSsc as it is documented
> > > as 'No BIOS override'. With this change I got more then 1000 soft and
> > > 2000 hard reboots
> > > without any problem. Keep in mind we started with only 10 successful reboots.
> >
> > Please be more specific about the final setting of this UPD. `No BIOS
> > override` is the documentation for the default value of 0xff. But is
> > this set to the default in the binary? who knows...
>
> void mainboard_memory_init_params(FSPM_UPD *mupd)
> {
>     FSP_M_CONFIG *mem_cfg;
>     struct spd_block blk = {
>         .addr_map = { 0x50 },
>     };
> mem_cfg = &mupd->FspmConfig;
>
> /* Disable PCIe Spread Spectrum Clocking */
> printk(BIOS_ERR, "PegDisableSpreadSpectrumClocking: %x\n",
>
> mem_cfg->PegDisableSpreadSpectrumClocking);
>     printk(BIOS_ERR, "PchPmPciePllSsc: %x\n", mem_cfg->PchPmPciePllSsc);
>     mem_cfg->PegDisableSpreadSpectrumClocking = 1;
> get_spd_smbus(&blk);
> dump_spd_info(&blk);
> assert(blk.spd_array[0][0] != 0);
>
> mainboard_fill_dq_map_data(&mem_cfg->DqByteMapCh0);
> mainboard_fill_dqs_map_data(&mem_cfg->DqsMapCpu2DramCh0);
> mainboard_fill_rcomp_res_data(&mem_cfg->RcompResistor);
> mainboard_fill_rcomp_strength_data(&mem_cfg->RcompTarget);
>
> mem_cfg->DqPinsInterleaved = TRUE;
> mem_cfg->MemorySpdDataLen = blk.len;
> mem_cfg->MemorySpdPtr00 = (uintptr_t) blk.spd_array[0];
>
> }
>
> And here is the output taken from cbmem -1:
>
> ..
> FMAP: base = ff000000 size = 1000000 #areas = 4
> FMAP: area RW_MRC_CACHE found @ a50000 (65536 bytes)
> MRC: no data in 'RW_MRC_CACHE'
> PegDisableSpreadSpectrumClocking: 0
> PchPmPciePllSsc: ff
> SPD @ 0x50
> SPD: module type is DDR4
> ..
> > > The big problem is that PegDisableSpreadSpectrumClocking has no effect
> > > at all. I measured
> > > the freq it is not the 100MHz as expected. And I need to have a stable
> > > 100MHz this clock source
> > > is used internally by the FPGA to drive internal clocks. The end
> > > results is that EtherCAT is not
> > > able to sync.
> >
> > This setting is about a different clock, I guess. Can you please clarify
> > what is connected to which clock on your board.
>
> Our FPGAs are using the 100 MHz PCIe clock as input to drive internal
> clocks etc. One
> of these clock is used for EtherCAT. If spread spectrum is active we
> are around 100 MHz
> (worst measured freq was ~92 MHz) and as a result the internal FPGA clock is not
> stable/reliable --> EtherCAT sync fails.
>
> If I use the following pattern:
> mem_cfg->PegDisableSpreadSpectrumClocking = 1;
> mem_cfg->PchPmPciePllSsc = 0;
>
> I get a stable 100 MHz PCIe clock signal and everything works - except
> the device hangs
> after < 10 warm reboots. Looks like PCIe link training fails
> uncountable times (seen with protocol
> analyzer).
>
> https://christian-gmeiner.info