Hi All Looking at par 3.13 of "Synopsis DesignWare Cores PCI Express Controller Databook" v4.20a (pag 159) I've found: <<Speed Changing When you set the default of the Directed Speed Change field of the Link Width and Speed Change Control register (GEN2_CTRL_OFF . DIRECT_SPEED_CHANGE) using the DEFAULT_GEN2_SPEED_CHANGE configuration parameter to "1", then the speed change is initiated automatically after link up, and the core clears the contents of GEN2_CTRL_OFF . DIRECT_SPEED_CHANGE. If you want to prevent this automatic speed change, then write a lower speed value to the Target Link Speed field of the Link Control 2 register (LINK_CONTROL2_LINK_STATUS2_REG . PCIE_CAP_TARGET_LINK_SPEED) through the DBI before link up.>> So my interpretation would be that at init phase it would be correct to trigger the DIRECT_SPPED_CHANGE before the link is up; that is it seems correct to me to move that part of the code before link up. Does anybody have any idea about this? Many Thanks Gab > -----Original Message----- > From: Wangzhou (B) > Sent: Tuesday, April 14, 2015 8:21 AM > To: linux-pci@xxxxxxxxxxxxxxx > Cc: zhangjukuo; Gabriele Paoloni; Liguozhu (Kenneth) > Subject: [Query] PORT_LOGIC_SPEED_CHANGE set in PCIe designware driver > > Hi All, > > In pcie-designware.c, it sets the PORT_LOGIC_SPEED_CHANGE bit after > linkup > finished: > > dw_pcie_rd_own_conf(pp, PCIE_LINK_WIDTH_SPEED_CONTROL, 4, &val); val |= > PORT_LOGIC_SPEED_CHANGE; dw_pcie_wr_own_conf(pp, > PCIE_LINK_WIDTH_SPEED_CONTROL, 4, val); > > As far as I know, it will try to use 5G/8G to communicate after setting > this bit. When I used LSI SAS2208 PCIe-RAID card to test PCIe host > driver, PCIe3.0 link was unstable and can not read/write PCIe-RAID BAR. > When I moved above code before linkup, the process of enumeration was > successful. > > I wonder if anyone who also use the pcie-designware had met the same > problem. > Could we move the PORT_LOGIC_SPEED_CHANGE before linkup? > > It will be very appreciate if anyone can offer some information. > > Thanks, > Zhou -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
