Hi Nadeem,
On 19/10/20 10:48 pm, Athani Nadeem Ladkhan wrote:
> Hi Kishon,
>
>> -----Original Message-----
>> From: Kishon Vijay Abraham I <kishon@xxxxxx>
>> Sent: Monday, October 19, 2020 10:59 AM
>> To: Athani Nadeem Ladkhan <nadeem@xxxxxxxxxxx>;
>> lorenzo.pieralisi@xxxxxxx; robh@xxxxxxxxxx; bhelgaas@xxxxxxxxxx; linux-
>> pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Tom Joseph
>> <tjoseph@xxxxxxxxxxx>
>> Cc: Swapnil Kashinath Jakhade <sjakhade@xxxxxxxxxxx>; Milind Parab
>> <mparab@xxxxxxxxxxx>
>> Subject: Re: [PATCH v3] PCI: cadence: Retrain Link to work around Gen2
>> training defect.
>>
>> EXTERNAL MAIL
>>
>>
>> Hi Nadeem,
>>
>> On 30/09/20 11:51 pm, Nadeem Athani wrote:
>>> Cadence controller will not initiate autonomous speed change if
>>> strapped as Gen2. The Retrain Link bit is set as quirk to enable this speed
>> change.
>>>
>>> Signed-off-by: Nadeem Athani <nadeem@xxxxxxxxxxx>
>>> ---
>>> Changes in v3:
>>> - To set retrain link bit,checking device capability & link status.
>>> - 32bit read in place of 8bit.
>>> - Minor correction in patch comment.
>>> - Change in variable & macro name.
>>> Changes in v2:
>>> - 16bit read in place of 8bit.
>>> drivers/pci/controller/cadence/pcie-cadence-host.c | 31
>> ++++++++++++++++++++++
>>> drivers/pci/controller/cadence/pcie-cadence.h | 9 ++++++-
>>> 2 files changed, 39 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c
>>> b/drivers/pci/controller/cadence/pcie-cadence-host.c
>>> index 4550e0d469ca..2b2ae4e18032 100644
>>> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
>>> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
>>> @@ -77,6 +77,36 @@ static struct pci_ops cdns_pcie_host_ops = {
>>> .write = pci_generic_config_write,
>>> };
>>>
>>> +static void cdns_pcie_retrain(struct cdns_pcie *pcie) {
>>> + u32 lnk_cap_sls, pcie_cap_off = CDNS_PCIE_RP_CAP_OFFSET;
>>> + u16 lnk_stat, lnk_ctl;
>>> +
>>> + if (!cdns_pcie_link_up(pcie))
>>> + return;
>>> +
>>
>> Is there a IP version that can be used to check if that quirk is applicable?
> There is no such provision.
hmm okay. Can we add a DT property to indicate the quirk then since
AFAIK this is not required in future revisions of IP.
>>> + /*
>>> + * Set retrain bit if current speed is 2.5 GB/s,
>>> + * but the PCIe root port support is > 2.5 GB/s.
>>> + */
>>> +
>>> + lnk_cap_sls = cdns_pcie_readl(pcie, (CDNS_PCIE_RP_BASE +
>> pcie_cap_off +
>>> + PCI_EXP_LNKCAP));
>>> + if ((lnk_cap_sls & PCI_EXP_LNKCAP_SLS) <=
>> PCI_EXP_LNKCAP_SLS_2_5GB)
>>> + return;
>>> +
>>> + lnk_stat = cdns_pcie_rp_readw(pcie, pcie_cap_off +
>> PCI_EXP_LNKSTA);
>>> + if ((lnk_stat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB)
>> {
>>> + lnk_ctl = cdns_pcie_rp_readw(pcie,
>>> + pcie_cap_off + PCI_EXP_LNKCTL);
>>> + lnk_ctl |= PCI_EXP_LNKCTL_RL;
>>> + cdns_pcie_rp_writew(pcie, pcie_cap_off + PCI_EXP_LNKCTL,
>>> + lnk_ctl);
>>> +
>>> + if (!cdns_pcie_link_up(pcie))
>>
>> Should this rather be a cdns_pcie_host_wait_for_link()?
> The use of this api cdns_pcie_link_up was mentioned in earlier reviews.
> The mentioned api cdns_pcie_host_wait_for_link is a wrapper in which there are multiple checks.
> If insist, will replace with it.
yeah, I think we should give some time for the link up to succeed after
re-training.
Thanks
Kishon
