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

[York Sun]

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