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SubjectRe: [PATCH V5 5/5] PCI: tegra: Disable LTSSM during L2 entry
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On 12/8/2020 2:07 AM, Bjorn Helgaas wrote:
> External email: Use caution opening links or attachments
>
>
> [+cc Jingoo, Gustavo]
>
> On Thu, Dec 03, 2020 at 07:04:51PM +0530, Vidya Sagar wrote:
>> PCIe cards like Marvell SATA controller and some of the Samsung NVMe
>> drives don't support taking the link to L2 state. When the link doesn't
>> go to L2 state, Tegra194 requires the LTSSM to be disabled to allow PHY
>> to start the next link up process cleanly during suspend/resume sequence.
>> Failing to disable LTSSM results in the PCIe link not coming up in the
>> next resume cycle.
>
> Is this a Tegra194-specific issue, or will other DWC-based controllers
> need a similar change?
This is a Tegra194 specific issue.

Thanks,
Vidya Sagar
>
>> Tested-by: Thierry Reding <treding@nvidia.com>
>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
>> Acked-by: Thierry Reding <treding@nvidia.com>
>> ---
>> V5:
>> * Added Tested-by and Acked-by from Thierry Reding
>>
>> V4:
>> * New patch in this series
>>
>> drivers/pci/controller/dwc/pcie-tegra194.c | 16 +++++++++-------
>> 1 file changed, 9 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
>> index f4109d71f20b..5597b2a49598 100644
>> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
>> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
>> @@ -1506,6 +1506,14 @@ static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
>> data &= ~APPL_PINMUX_PEX_RST;
>> appl_writel(pcie, data, APPL_PINMUX);
>>
>> + /*
>> + * Some cards do not go to detect state even after de-asserting
>> + * PERST#. So, de-assert LTSSM to bring link to detect state.
>> + */
>> + data = readl(pcie->appl_base + APPL_CTRL);
>> + data &= ~APPL_CTRL_LTSSM_EN;
>> + writel(data, pcie->appl_base + APPL_CTRL);
>> +
>> err = readl_poll_timeout_atomic(pcie->appl_base + APPL_DEBUG,
>> data,
>> ((data &
>> @@ -1513,14 +1521,8 @@ static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
>> APPL_DEBUG_LTSSM_STATE_SHIFT) ==
>> LTSSM_STATE_PRE_DETECT,
>> 1, LTSSM_TIMEOUT);
>> - if (err) {
>> + if (err)
>> dev_info(pcie->dev, "Link didn't go to detect state\n");
>> - } else {
>> - /* Disable LTSSM after link is in detect state */
>> - data = appl_readl(pcie, APPL_CTRL);
>> - data &= ~APPL_CTRL_LTSSM_EN;
>> - appl_writel(pcie, data, APPL_CTRL);
>> - }
>> }
>> /*
>> * DBI registers may not be accessible after this as PLL-E would be
>> --
>> 2.17.1
>>

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