On Fri, 2024-03-08 at 14:02 +0100, AngeloGioacchino Del Regno wrote:
> Il 08/03/24 10:44, Jianjun Wang (王建军) ha scritto:
> > On Wed, 2024-03-06 at 09:50 +0100, AngeloGioacchino Del Regno
> > wrote:
> > > 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@xxxxxxxxxxxxx>
> > > > > ---
> > > > >
> > > > > 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).
> >
> > Does this only happen when the PCIe MAC is reset without resetting
> > the
> > PHY? Is it related to the reset framework?
> >
>
> Happens only when MAC is reset without resetting the PHY after
> calling
> phy_power_off(); phy_exit();
>
> It's not a reset framework issue, that's for sure.
Thanks for the explanation.
In that case, why do we only reset during suspend? Can we also reset
them when probe fails and driver removing, if both the PHY and MAC
resets are present?
Thanks.
>
> Angelo
>
> > Thanks.
> > >
> > > 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;
> > > > > }
> > > > >
> > >
> > >
> > >
>
>
