Hi Bjorn, Rob, Lorenzo, Could you please help to take a look at this patch, I'm not sure if this is a good solution, and I really need your suggestions. Thanks. On Fri, 2021-05-14 at 14:59 +0800, Jianjun Wang wrote: > PCIe Gen3 PHY layer cannot work properly when the requested voltage > is lower than a specific level(e.g. 0.55V, it's depends on > the chip manufacturing process). > > When the dvfsrc feature is implemented, the requested voltage > may be reduced to a lower level in suspend mode, hence that > the MAC layer will assert a HW signal to request the dvfsrc > to raise voltage to normal mode, and it will wait the voltage > ready signal which is derived from dvfsrc to determine whether > the LTSSM can start normally. > > When the dvfsrc feature is not implemented, the MAC layer still > assert the voltage request to dvfsrc when exit suspend mode, > but will not receive the voltage ready signal, in this case, > the LTSSM cannot start normally, and the PCIe link will be failed. > > Add support for disable dvfsrc voltage request. If the property of > "disable-dvfsrc-vlt-req" is presented in device node, we assume that > the requested voltage is always higher enough to keep the PCIe Gen3 > PHY active, and the voltage request to dvfsrc should be disabled. > > Signed-off-by: Jianjun Wang <jianjun.wang@xxxxxxxxxxxx> > --- > drivers/pci/controller/pcie-mediatek-gen3.c | 32 +++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c > index 20165e4a75b2..d1864303217e 100644 > --- a/drivers/pci/controller/pcie-mediatek-gen3.c > +++ b/drivers/pci/controller/pcie-mediatek-gen3.c > @@ -68,6 +68,9 @@ > #define PCIE_MSI_SET_ENABLE_REG 0x190 > #define PCIE_MSI_SET_ENABLE GENMASK(PCIE_MSI_SET_NUM - 1, 0) > > +#define PCIE_MISC_CTRL_REG 0x348 > +#define PCIE_DISABLE_DVFSRC_VLT_REQ BIT(1) > + > #define PCIE_MSI_SET_BASE_REG 0xc00 > #define PCIE_MSI_SET_OFFSET 0x10 > #define PCIE_MSI_SET_STATUS_OFFSET 0x04 > @@ -297,6 +300,35 @@ static int mtk_pcie_startup_port(struct mtk_pcie_port *port) > val &= ~PCIE_INTX_ENABLE; > writel_relaxed(val, port->base + PCIE_INT_ENABLE_REG); > > + /* > + * PCIe Gen3 PHY layer can not work properly when the requested voltage > + * is lower than a specific level(e.g. 0.55V, it's depends on > + * the chip manufacturing process). > + * > + * When the dvfsrc feature is implemented, the requested voltage > + * may be reduced to a lower level in suspend mode, hence that > + * the MAC layer will assert a HW signal to request the dvfsrc > + * to raise voltage to normal mode, and it will wait the voltage > + * ready signal which is derived from dvfsrc to determine whether > + * the LTSSM can start normally. > + * > + * When the dvfsrc feature is not implemented, the MAC layer still > + * assert the voltage request to dvfsrc when exit suspend mode, > + * but will not receive the voltage ready signal, in this case, > + * the LTSSM cannot start normally, and the PCIe link will be failed. > + * > + * If the property of "disable-dvfsrc-vlt-req" is presented > + * in device node, we assume that the requested voltage is always > + * higher enough to keep the PCIe Gen3 PHY active, and the voltage > + * request to dvfsrc should be disabled. > + */ > + val = readl_relaxed(port->base + PCIE_MISC_CTRL_REG); > + val &= ~PCIE_DISABLE_DVFSRC_VLT_REQ; > + if (of_property_read_bool(port->dev->of_node, "disable-dvfsrc-vlt-req")) > + val |= PCIE_DISABLE_DVFSRC_VLT_REQ; > + > + writel(val, port->base + PCIE_MISC_CTRL_REG); > + > /* Assert all reset signals */ > val = readl_relaxed(port->base + PCIE_RST_CTRL_REG); > val |= PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB;
