On Tue, Oct 10, 2023 at 06:42:07PM +0200, Frank Wunderlich wrote: > Am 10. Oktober 2023 18:04:23 MESZ schrieb Bjorn Helgaas <helgaas@xxxxxxxxxx>: > >On Fri, Oct 06, 2023 at 09:45:58AM +0200, Daniel Golle wrote: > >> The driver for MediaTek gen3 PCIe hosts de-asserts all reset > >> signals at the same time using a single register write operation. > >> Delay the de-assertion of the #PERST signal by 100ms as required by > >> PCIe CEM clause 2.2, some PCIe devices fail to come up otherwise. > >> > >> Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx> > >> --- > >> drivers/pci/controller/pcie-mediatek-gen3.c | 8 +++++++- > >> 1 file changed, 7 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c > >> index e0e27645fdf4..ba8cfce03aad 100644 > >> --- a/drivers/pci/controller/pcie-mediatek-gen3.c > >> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c > >> @@ -350,7 +350,13 @@ static int mtk_pcie_startup_port(struct mtk_gen3_pcie *pcie) > > > >I feel like I'm missing something because this patch seems to be > >adding a delay for T_PVPERL, but the comment before the existing > >msleep() claims *it* is the T_PVPERL delay: > > > > * 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 reset signals */ > >> - val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB | PCIE_PE_RSTB); > >> + val &= ~(PCIE_MAC_RSTB | PCIE_PHY_RSTB | PCIE_BRG_RSTB); > >> + writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG); > >> + > >> + msleep(100); > > > >So I'm confused about these two sleeps. Are they for different > >parameters? > > > >T_PVPERL is defined from "Power stable to PERST# inactive". Do we > >have any actual indication of when to start that delay, i.e., do we > >have a clue about when power became stable? > > > >> + /* De-assert PERST# signals */ > >> + val &= ~(PCIE_PE_RSTB); > >> writel_relaxed(val, pcie->base + PCIE_RST_CTRL_REG); > >> > >> /* Check if the link is up or not */ > >> -- > >> 2.42.0 > >> > >> > >> _______________________________________________ > >> linux-arm-kernel mailing list > >> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > Hi > > Seems it is same as the patch i've sent some time ago and which was rejected because of the additional delay... > > https://patchwork.kernel.org/project/linux-mediatek/patch/20230402131347.99268-1-linux@xxxxxxxxx/ > > Or am i wrong? > regards Frank Reading the other series, I smell this can only be handled by a quirk... This might be a defect or the board not following PCIE hw specs. Thing is that the bug/limitation is there and we have enough info to find way to fix this and lots of tester. Eventually even a fixup based on a specific compatible. -- Ansuel
