On Thu, Feb 29, 2024 at 10:24:49AM +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);
Wouldn't this power off the shared PHY? Or will the PHY driver make this
NO-OP if the PHY is shared, in which case the above two statements could
be combined with the other statements in the:
if (is_suspend && suspend_reset_supported)
condition to get a single block of code that also combines the
reset_control_assert(pcie->phy_reset)
present below.
> - reset_control_assert(pcie->phy_reset);
> + if (is_suspend && suspend_reset_supported)
> + reset_control_assert(pcie->phy_reset);
> }
>
...
Regards,
Siddharth.
