On 28/06/2022 10:13, Marek Szyprowski wrote: > Hi Krzysztof, > > On 27.06.2022 12:47, Krzysztof Kozlowski wrote: >> On 27/06/2022 12:30, Marek Szyprowski wrote: >>> On 24.06.2022 20:07, Krzysztof Kozlowski wrote: >>>> On 24/06/2022 19:35, Bjorn Helgaas wrote: >>>>> In exynos_pcie_host_init() [1], we call: >>>>> >>>>> phy_reset(ep->phy); >>>>> phy_power_on(ep->phy); >>>>> phy_init(ep->phy); >>>>> >>>>> The phy_init() function comment [2] says it must be called before >>>>> phy_power_on(). Is exynos doing this backwards? >>>> Looks like. I don't have Exynos hardware with a PCI, so cannot >>>> test/fix/verify. >>>> >>>> Luckily for Exynos ;-) it's not alone in this pattern: >>>> drivers/net/ethernet/marvell/sky2.c >>>> drivers/usb/dwc2/platform.c >>> I've checked that on the real hardware. Swapping the order of >>> phy_power_on and phy_init breaks driver operation. >>> >>> However pci-exynos is the only driver that uses the phy-exynos-pcie, so >>> we can simply swap the content of the init and power_on in the phy >>> driver to adjust the code to the right order. power_on/init and >>> exit/power_off are also called one after the other in pci-exynos, >>> without any activity between them, so we can also simply move all >>> operation to one pair of the callback, like power_on/off. >>> >>> Krzysztof, which solution would you prefer? >> I think the real problem is that the Exynos PCIe phy init >> (exynos5433_pcie_phy_init) performs parts of power on procedure, so the >> code is mixed. Probably also the phy init could not happen earlier due >> to gated clocks (ungated in exynos5433_pcie_phy_power_on). >> >> I would prefer to clean it up while ordering init+power_on, so figure >> out more or less correct procedure. >> >> You can also look at Artpec-8 PHY - it seems using correct order >> (init+reset): >> https://lore.kernel.org/all/20220614011616epcms2p7dcaa67c53b7df5802dd7a697e2d472d7@epcms2p7/ > > I've played a bit with those register writes in exynos_pcie_phy and > frankly speaking the currenly used (power_on + init) is the only > sequence that works properly. I'm leaning to move everything to > phy_init/exit. I really don't see how to split it into init + power_on > callbacks. I was afraid it will be like this. I imagine that certain (not explicitly documented) init operations cannot even happen before power on, so this would be a lot of tries. I am fine with it. Thanks for doing it. > > While touching this - I would also remove the phy_reset() call in the > exynos-pcie driver. It is a left over from the old, obsoleted exynos5440 > pcie code, not implemented in the current phy driver, also only a few > drivers use or implement it. IMHO it doesn't make sense to keep such > dead code. Sure, looks ok. Best regards, Krzysztof
