On Tue, Dec 07, 2021 at 11:54:16AM -0600, Bjorn Helgaas wrote: > [+cc Marc, Alyssa, Mark, Luca for reset timing questions] > > On Tue, Dec 07, 2021 at 04:41:53PM +0800, qizhong cheng wrote: > > Described in PCIe CEM specification sections 2.2 (PERST# Signal) and > > 2.2.1 (Initial Power-Up (G3 to S0)). The deassertion of PERST# should > > be delayed 100ms (TPVPERL) for the power and clock to become stable. > > > > Signed-off-by: qizhong cheng <qizhong.cheng@xxxxxxxxxxxx> > > Acked-by: Pali Roh�r <pali@xxxxxxxxxx> > > --- > > > > v2: > > - Typo fix. > > - Rewrap into one paragraph. > > 1) If you change something, even in the commit log or comments, it is > a new version, not a "RESEND". A "RESEND" means "I sent this quite a > while ago and didn't hear anything, so I'm sending the exact same > thing again in case the first one got lost." > > 2) I suggested a subject line update, which apparently got missed. > Here's a better one: > > PCI: mediatek: Assert PERST# for 100ms for power and clock to stabilize > > 3) Most importantly, this needs to be reconciled with the similar > change to the apple driver: > > https://lore.kernel.org/r/20211123180636.80558-2-maz@xxxxxxxxxx > > In the apple driver, we're doing: > > - Assert PERST# > - Set up REFCLK > - Sleep 100us (T_perst-clk, CEM r5 2.2, 2.9.2) > - Deassert PERST# > - Sleep 100ms (not sure there's a name? PCIe r5 6.6.1) > > But here in mediatek, we're doing: > > - Assert PERST# > - Sleep 100ms (T_pvperl, CEM r5 2.2, 2.2.1, 2.9.2) > - Deassert PERST# > > My questions: > > - Where does apple enforce T_pvperl? I can't tell where power to > the slot is turned on. > > - Where does mediatek enforce the PCIe sec 6.6.1 delay after > deasserting PERST# and before config requests? > > - Does either apple or mediatek support speeds greater than 5 GT/s, > and if so, shouldn't we start the sec 6.6.1 100ms delay *after* > Link training completes? I dropped this patch from my pci/mediatek branch, waiting for clarification. Thanks, Lorenzo > > drivers/pci/controller/pcie-mediatek.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c > > index 2f3f974977a3..a61ea3940471 100644 > > --- a/drivers/pci/controller/pcie-mediatek.c > > +++ b/drivers/pci/controller/pcie-mediatek.c > > @@ -702,6 +702,13 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port) > > */ > > writel(PCIE_LINKDOWN_RST_EN, port->base + PCIE_RST_CTRL); > > > > + /* > > + * Described in PCIe CEM specification sections 2.2 (PERST# Signal) and > > + * 2.2.1 (Initial Power-Up (G3 to S0)). The deassertion of PERST# should > > + * be delayed 100ms (TPVPERL) for the power and clock to become stable. > > + */ > > + msleep(100); > > + > > /* De-assert PHY, PE, PIPE, MAC and configuration reset */ > > val = readl(port->base + PCIE_RST_CTRL); > > val |= PCIE_PHY_RSTB | PCIE_PERSTB | PCIE_PIPE_SRSTB | > > -- > > 2.25.1 > >
