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SubjectRe: [PATCH v2] PCI: mediatek-gen3: Assert MAC reset only if PHY reset also present
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Il 01/03/24 03:48, Jianjun Wang (王建军) ha scritto:
> Hi Angelo,
>
> Thanks for your patch.
>
> On Thu, 2024-02-29 at 10:24 +0100, AngeloGioacchino Del Regno wrote:
>> Some SoCs have two PCI-Express controllers: in the case of MT8195,
>> one of them is using a dedicated PHY, but the other uses a combo PHY
>> that is shared with USB and in that case the PHY cannot be reset
>> from the PCIe driver, or USB functionality will be unable to resume.
>>
>> Resetting the PCIe MAC without also resetting the PHY will result in
>> a full system lockup at PCIe resume time and the only option to
>> resume operation is to hard reboot the system (with a PMIC cut-off).
>>
>> To resolve this issue, check if we've got both a PHY and a MAC reset
>> and, if not, never assert resets at PM suspend time: in that case,
>> the link is still getting powered down as both the clocks and the
>> power domains will go down anyway.
>>
>> Fixes: d537dc125f07 ("PCI: mediatek-gen3: Add system PM support")
>> Signed-off-by: AngeloGioacchino Del Regno <
>> angelogioacchino.delregno@collabora.com>
>> ---
>>
>> Changes in v2:
>> - Rebased over next-20240229
>>
>> drivers/pci/controller/pcie-mediatek-gen3.c | 25 ++++++++++++++-----
>> --
>> 1 file changed, 17 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c
>> b/drivers/pci/controller/pcie-mediatek-gen3.c
>> index 975b3024fb08..99b5d7a49be1 100644
>> --- a/drivers/pci/controller/pcie-mediatek-gen3.c
>> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
>> @@ -874,17 +874,26 @@ static int mtk_pcie_power_up(struct
>> mtk_gen3_pcie *pcie)
>> return err;
>> }
>>
>> -static void mtk_pcie_power_down(struct mtk_gen3_pcie *pcie)
>> +static void mtk_pcie_power_down(struct mtk_gen3_pcie *pcie, bool
>> is_suspend)
>> {
>> + bool suspend_reset_supported = pcie->mac_reset && pcie-
>>> phy_reset;
>> +
>> clk_bulk_disable_unprepare(pcie->num_clks, pcie->clks);
>>
>> pm_runtime_put_sync(pcie->dev);
>> pm_runtime_disable(pcie->dev);
>> - reset_control_assert(pcie->mac_reset);
>> +
>> + /*
>> + * Assert MAC reset only if we also got a PHY reset, otherwise
>> + * the system will lockup at PM resume time.
>> + */
>> + if (is_suspend && suspend_reset_supported)
>> + reset_control_assert(pcie->mac_reset);
>>
>> phy_power_off(pcie->phy);
>> phy_exit(pcie->phy);
>> - reset_control_assert(pcie->phy_reset);
>> + if (is_suspend && suspend_reset_supported)
>> + reset_control_assert(pcie->phy_reset);
>> }
>>
>> static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
>> @@ -920,7 +929,7 @@ static int mtk_pcie_setup(struct mtk_gen3_pcie
>> *pcie)
>> return 0;
>>
>> err_setup:
>> - mtk_pcie_power_down(pcie);
>> + mtk_pcie_power_down(pcie, false);
>>
>> return err;
>> }
>> @@ -951,7 +960,7 @@ static int mtk_pcie_probe(struct platform_device
>> *pdev)
>> err = pci_host_probe(host);
>> if (err) {
>> mtk_pcie_irq_teardown(pcie);
>> - mtk_pcie_power_down(pcie);
>> + mtk_pcie_power_down(pcie, false);
>> return err;
>> }
>>
>> @@ -969,7 +978,7 @@ static void mtk_pcie_remove(struct
>> platform_device *pdev)
>> pci_unlock_rescan_remove();
>>
>> mtk_pcie_irq_teardown(pcie);
>> - mtk_pcie_power_down(pcie);
>> + mtk_pcie_power_down(pcie, false);
>
> Is there any reason not to reset the MAC and PHY when probe fails and
> driver removing? Some SoCs may not have MTCMOS to cut off their power,
> we need to assert the reset signal to save power in that case.
>

Sorry for the late reply - yes, there is a reason.

On platforms needing this quirk, resetting at .remove() time will hang the
machine if the module is reinserted later (hence, .probe() called at a later
time).

Regards,
Angelo

> Thanks.
>
>> }
>>
>> static void mtk_pcie_irq_save(struct mtk_gen3_pcie *pcie)
>> @@ -1044,7 +1053,7 @@ static int mtk_pcie_suspend_noirq(struct device
>> *dev)
>> dev_dbg(pcie->dev, "entered L2 states successfully");
>>
>> mtk_pcie_irq_save(pcie);
>> - mtk_pcie_power_down(pcie);
>> + mtk_pcie_power_down(pcie, true);
>>
>> return 0;
>> }
>> @@ -1060,7 +1069,7 @@ static int mtk_pcie_resume_noirq(struct device
>> *dev)
>>
>> err = mtk_pcie_startup_port(pcie);
>> if (err) {
>> - mtk_pcie_power_down(pcie);
>> + mtk_pcie_power_down(pcie, false);
>> return err;
>> }
>>



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