[U-Boot] setup of PEX_GCLK_RATIO in E500 CPUs(P2010) missing ?

Wed Sep 6 09:36:51 UTC 2017

> -----Original Message-----
> From: Joakim Tjernlund [mailto:Joakim.Tjernlund at infinera.com]
> Sent: Tuesday, September 05, 2017 8:45 PM
> To: Mingkai Hu <mingkai.hu at nxp.com>; Roy Zang <roy.zang at nxp.com>;
> York Sun <york.sun at nxp.com>
> Cc: u-boot at lists.denx.de
> Subject: Re: setup of PEX_GCLK_RATIO in E500 CPUs(P2010) missing ?
> 
> On Wed, 2017-08-30 at 15:25 +0000, York Sun wrote:
> > On 08/30/2017 06:05 AM, Joakim Tjernlund wrote:
> > > On Tue, 2017-08-29 at 17:33 +0000, York Sun wrote:
> > > > +Roy Zang to comment on PCIe clock source
> > > >
> > > > On 08/29/2017 10:06 AM, Joakim Tjernlund wrote:
> > > > > On Tue, 2017-08-29 at 15:43 +0000, York Sun wrote:
> > > > > > On 08/29/2017 06:21 AM, Joakim Tjernlund wrote:
> > > > > > > On Tue, 2017-08-29 at 12:47 +0200, Joakim Tjernlund wrote:
> > > > > > > > As we are looking at PCI stuff ATM I would like to ask
> > > > > > > > about PEX_GCLK_RATIO in E500 CPUs. I cannot find this is
> > > > > > > > setup at all for E500 but I THINK this is required.
> > > > > > > >
> > > > > > > > In 83xx one do:
> > > > > > > > get_clocks();
> > > > > > > > /* Configure the PCIE controller core clock ratio */
> > > > > > > > out_le32(hose_cfg_base + PEX_GCLK_RATIO,
> > > > > > >
> > > > > > > A bit strange with out_le32 instead of out_be32 ?
> > > > > > >
> > > > > > > > (((bus ? gd->arch.pciexp2_clk : gd->arch.pciexp1_clk) /
> > > > > > > > 1000000) * 16) / 333); udelay(1000000);
> > > > > > > >
> > > > > > > > Any clues?
> > > > > > > >
> > > > > > > >     Jocke
> > > > > > >
> > > > > > > Seems like only 83xx is setting this parameter.
> > > > > > >
> > > > > > > Anyhow, I put together this patch:
> > > > > > >
> > > > > > > --- a/drivers/pci/fsl_pci_init.c
> > > > > > > +++ b/drivers/pci/fsl_pci_init.c
> > > > > > > @@ -322,6 +322,10 @@ void fsl_pci_init(struct pci_controller
> > > > > > > *hose, struct fsl_pci_info *pci_info)
> > > > > > >
> > > > > > >            pci_setup_indirect(hose, cfg_addr, cfg_data);
> > > > > > >
> > > > > > > +       /* Configure the PCIE controller core clock ratio */
> > > > > > > +       pci_hose_write_config_dword(hose, dev, 0x440, (gd-
> >bus_clk / 333333333) * 16);
> > > > > > > +       /* udelay(1000000) needed here ?*/
> > > > > > > +
> > > > > > >            block_rev = in_be32(&pci->block_rev1);
> > > > > > >            if (PEX_IP_BLK_REV_2_2 <= block_rev) {
> > > > > > >                    pi = &pci->pit[2];      /* 0xDC0 */
> > > > > > >
> > > > > > > Any chance this will work for all supported FSL PCIe controllers?
> > > > > > >
> > > > > >
> > > > > > Jocke,
> > > > > >
> > > > > > You don't need to program this register if the actual PCIe
> > > > > > clock is the same as default. Since SerDes reference clock has
> > > > > > to be 100MHz for PCIe protocol, my guess is the PCIe clock is
> > > > > > always correct. The bus_clk you are referring is not the PCIe
> > > > > > clock. Again, I am not a PCIe expert, I could be wrong. Since
> > > > > > PCIe (SerDes) has been working on multiple platforms, I guess the
> clock is correct.
> > > > >
> > > > > I don't think so. Here is what T1042 says about this:
> > > > >
> > > > > The PCI Express controller clock frequency is one-half the platform
> clock frequency.
> > > > >
> > > > > The PCI Express controller core clock ratio register is used to
> > > > > program the ratio of the actual PCI Express controller clock
> > > > > frequency to the default controller core frequency ( 333 MHz ).
> > > > > This is required only when a PCI Express controller clock frequency
> other than the default 333 MHz has to be used.
> > > > > As an example of programming PEX_GCLK_RATIO, consider the case
> > > > > where the actual PCI Express controller clock is 250 MHz, the
> > > > > ratio of the actual clock to the default clock ( 333 MHz) is
> > > > > 3:4. that is, the default core clock has to be multiplied by the
> > > > > ratio (3/4, which is equivalent to 12/16). So the register has to be
> programmed with the decimal numerator value 12 or 0x0000_000C.
> > > > >
> > > > > Our CCB is 250 MHz so this should be set to 0xc.
> > > > >
> > > > > I found this on Google too:
> > > > > The PEX controller hardware requires for timing tuning in order
> > > > > to operate properly at given CCB/2 clock frequency.
> > > > > PEX_GCLK_RATIO register controls this tuning with 333MHz/16
> > > > > granularities. So for given CCB frequency Fccb [MHz] we must write to
> PEX_GCLK_RATIO nearest integer of ((Fccb/2)/(333/16)). So for Fccb=375 we
> have to write 18.
> > > >
> > > > Jocke,
> > > >
> > > > Basically I agree with you, if the clock is different from
> > > > default, you need to set the ratio. T104x indeed uses 1/2 platform
> > > > clock as PCIe clock. I am not sure if P2010 uses the same way. Let
> > > > me add Roy to this thread.
> > > >
> > > > Roy, how do we get PCIe clock for P1/T1 (and other mpc85xx) SoCs?
> > > > Don't we need to set PEX_GCLK_RATIO register? It is not even in the
> header file.
> > >
> > > Patch was off, this works:
> > > diff --git a/drivers/pci/fsl_pci_init.c b/drivers/pci/fsl_pci_init.c
> > > index 52792dcd59..e7f2499784 100644
> > > --- a/drivers/pci/fsl_pci_init.c
> > > +++ b/drivers/pci/fsl_pci_init.c
> > > @@ -322,6 +322,11 @@ void fsl_pci_init(struct pci_controller *hose,
> > > struct fsl_pci_info *pci_info)
> > >
> > >          pci_setup_indirect(hose, cfg_addr, cfg_data);
> > >
> > > +       /* Configure the PCIE controller core clock ratio */
> > > +       pci_hose_write_config_dword(hose, dev, 0x440,
> >
> > pci_hose_write_config_dword() writes to config space, doesn't it?
> > 0x440 is not in config space.
> >
> > > +                                   ((gd->bus_clk / 1000000) * 16/2) / 333);
> > > +       /* udelay(1000000) needed here ?*/
> >
> > Let us not to add delay if we don't know yet.
> >
> > > +
> > >          block_rev = in_be32(&pci->block_rev1);
> > >          if (PEX_IP_BLK_REV_2_2 <= block_rev) {
> > >                  pi = &pci->pit[2];      /* 0xDC0 */
> > >
> > >
> > > Any news on this ?
> > > I know both T1042 and P2010 has the same setting/formula, a good
> > > start :)
> >
> > +Mingkai to comment on PCIe clock
> >
> > York
> 

This is the clock to PCIe controller which is not different from the clock to PCIe SerDes lane.
My understanding is that it should be configured according to the platform frequency.
But there is no specific and consistent description for all the platforms. I am checking with
the design team to see if there is hardware fixed clock to PCIe controller for the platforms
which don't have clear description. Will keep you all updated.

Regards,
Mingkai