Re: [PATCH RESEND v2] PCI: imx6: Enable ASPM L1 only iff CLKREQ# is supported

[Michal Gorlas]

On Thu Aug 27, 2026 at 7:10 PM CEST, Frank Li wrote:
> On Thu, Aug 27, 2026 at 06:51:00PM +0200, Michal Gorlas wrote:
>> Since commit f3ac2ff14834 ("PCI/ASPM: Enable all ClockPM and ASPM
>> states for devicetree platforms"), ASPM states are force enabled
>> on all devicetree platforms. This causes PCI devices on some i.MX SoCs
>> (for e.g. i.MX 8M Plus Kontron SMARC eval carrier) to enter L1 even
>> though CLKREQ# is not supported (and consequently supports-clkreq is
>> not set in pcie controller node of their DT), which causes the device to
>> never wake up from L1.
>>
>> Hence, disable L1 capability in the LNKCAP register if supports-clkreq
>> is not set in the DT explicitly. For devices that set
>> IMX_PCIE_FLAG_BROKEN_SUSPEND, disable L1 on resume as well, as these
>> skip imx_pcie_host_init().
>>
>> Note, the logic here is very similar to 613f3255a35a, only difference
>> is that leaving L0s enabled does not cause issues (at least
>> I never encountered them myself when testing on the device) as its
>> not dependent on CLKREQ# being physically there.
>> Since there is already a way of specifying its presence in the DT,
>> the driver should be aware and disable L1.
>>
>> Fixes: f3ac2ff14834 ("PCI/ASPM: Enable all ClockPM and ASPM states for devicetree platforms")
>> Signed-off-by: Michal Gorlas <michal.gorlas@xxxxxxxxxxxxx>
>> Tested-by: Richard Zhu <hongxing.zhu@xxxxxxx>
>> Reviewed-by: Richard Zhu <hongxing.zhu@xxxxxxx>
>> ---
>> Changes in v2:
>> - disable L1 unconditionally on resume for platforms advertising
>> IMX_PCIE_FLAG_BROKEN_SUSPEND (Sashiko)
>> - typos in the commit message
>> - Link to v1: https://patch.msgid.link/20260719-l1-conditional-imx-v1-1-a55a57915c68@xxxxxxxxxxxxx
>> ---
>>  drivers/pci/controller/dwc/pci-imx6.c | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
>> index 98e1db751132..1fdcbcd2422e 100644
>> --- a/drivers/pci/controller/dwc/pci-imx6.c
>> +++ b/drivers/pci/controller/dwc/pci-imx6.c
>> @@ -1318,6 +1318,22 @@ static void imx_pcie_assert_perst(struct imx_pcie *imx_pcie, bool assert)
>>  	}
>>  }
>>
>> +static void imx_pcie_disable_l1(struct dw_pcie *pci)
>> +{
>> +	u32 val;
>> +	u8 offset;
>> +
>> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>> +
>> +	dw_pcie_dbi_ro_wr_en(pci);
>> +
>> +	val = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
>> +	val &= ~PCI_EXP_LNKCAP_ASPM_L1;
>> +	dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, val);
>> +
>> +	dw_pcie_dbi_ro_wr_dis(pci);
>> +}
>> +
>>  static int imx_pcie_host_init(struct dw_pcie_rp *pp)
>>  {
>>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>> @@ -1442,6 +1458,9 @@ static int imx_pcie_host_init(struct dw_pcie_rp *pp)
>>
>>  	imx_setup_phy_mpll(imx_pcie);
>>
>> +	if (!imx_pcie->supports_clkreq)
>> +		imx_pcie_disable_l1(pci);
>> +
>>  	return 0;
>>
>>  err_phy_off:
>> @@ -1748,6 +1767,7 @@ static int imx_pcie_resume_noirq(struct device *dev)
>>  			return ret;
>>  		imx_pcie_deassert_core_reset(imx_pcie);
>>  		imx_pcie_assert_perst(imx_pcie, false);
>> +		imx_pcie_disable_l1(imx_pcie->pci);
>
> Does l1 disable permanent after resume? should it be
>
> 	if (!imx_pcie->supports_clkreq)
> 		mx_pcie_disable_l1(imx_pcie->pci);

It would be unnecessary, the imx_pcie_disable_l1() there is already
guarded by IMX_PCIE_FLAG_BROKEN_SUSPEND, so we know that only iMX6Q
ends up there on resume. And none of iMX6Q DT's sets supports-clkreq.

Best,
Michal
>
> Frank
>
>>
>>  		/*
>>  		 * Using PCIE_TEST_PD seems to disable MSI and powers down the
>>
>> ---
>> base-commit: a13c140cc289c0b7b3770bce5b3ad42ab35074aa
>> change-id: 20260713-l1-conditional-imx-c2bfd20ae085
>>
>> Best regards,
>> --
>> Michal Gorlas <michal.gorlas@xxxxxxxxxxxxx>
>>