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

[Joakim Tjernlund]

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,
+                                   ((gd->bus_clk / 1000000) * 16/2) / 333);
+       /* 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 news on this ?
I know both T1042 and P2010 has the same setting/formula, a good start :)

 Jocke