Hello Bjorn, > From: Bjorn Helgaas, Sent: Thursday, October 19, 2023 12:11 PM > > On Wed, Oct 18, 2023 at 05:56:16PM +0900, Yoshihiro Shimoda wrote: > > Add R-Car S4-8 (R-Car Gen4) PCIe controller for both host and endpoint modes. > > To support them, modify PCIe DesignWare common codes. > > > > Changes from v24: > > <snip URL> > > - Based on the latest pci.git / next branch. > > - Reordering the patches. (This is suggested by Bjorn.) > > - Drop "PCI: dwc: Disable two BARs to avoid unnecessary memory assignment" > > because break other platforms. > > Does R-Car Gen4 still work without this patch? Yes, R-Car Gen4 still work without this patch because I added this code into the patch 12/15 again: --- +static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp) +{ ... + /* + * According to the section 3.5.7.2 "RC Mode" in DWC PCIe Dual Mode + * Rev.5.20a and 3.5.6.1 "RC mode" in DWC PCIe RC databook v5.20a, we + * should disable two BARs to avoid unnecessary memory assignment + * during device enumeration. + */ + dw_pcie_writel_dbi2(dw, PCI_BASE_ADDRESS_0, 0x0); + dw_pcie_writel_dbi2(dw, PCI_BASE_ADDRESS_1, 0x0); --- I also mentioned about this on the cover-letter like below, but it may be difficult to understand. I'm sorry about lack explanation... I should have explained one sentence about that... >> - Add specific-setting by using dbi2 again in the patch 12/15. >> - Modify commend of the specific-setting in the patch 12/15. Serge suggested >> this on v23 but I missed to modify this on v24. > The previous commit log said host mode didn't work: > > PCI: dwc: Disable two BARs to avoid unnecessary memory assignment > > According to the section 3.5.7.2 "RC Mode" in DWC PCIe Dual Mode > Rev.5.20a, we should disable two BARs to avoid unnecessary memory > assignment during device enumeration. Otherwise, Renesas R-Car Gen4 > PCIe controllers cannot work correctly in host mode. > > (from https://lore.kernel.org/all/20231011071423.249458-9-yoshihiro.shimoda.uh@xxxxxxxxxxx/) > > I don't think we want to merge the driver unless it actually works. I understood it. Best regards, Yoshihiro Shimoda > Bjorn