+linux-mmc On Mon, 1 Jun 2020 at 09:34, 冯锐 <rui_feng@xxxxxxxxxxxxxx> wrote: > > > > > On Tue, 19 May 2020 at 11:18, 冯锐 <rui_feng@xxxxxxxxxxxxxx> wrote: > > > > > > > On Tue, 28 Apr 2020 at 05:44, 冯锐 <rui_feng@xxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > > On Mon, Apr 27, 2020 at 11:41 AM 冯锐 <rui_feng@xxxxxxxxxxxxxx> > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > On Sun, Apr 26, 2020 at 09:25:46AM +0800, > > > > > > > > rui_feng@xxxxxxxxxxxxxx > > > > > > wrote: > > > > > > > > > From: Rui Feng <rui_feng@xxxxxxxxxxxxxx> > > > > > > > > > > > > > > > > > > RTS5261 support legacy SD mode and SD Express mode. > > > > > > > > > In SD7.x, SD association introduce SD Express as a new mode. > > > > > > > > > SD Express mode is distinguished by CMD8. > > > > > > > > > Therefore, CMD8 has new bit for SD Express. > > > > > > > > > SD Express is based on PCIe/NVMe. > > > > > > > > > RTS5261 uses CMD8 to switch to SD Express mode. > > > > > > > > > > > > > > > > So how does this bit work? They way I imagined SD Express > > > > > > > > to work is that the actual SD Card just shows up as a real > > > > > > > > PCIe device, similar to say Thunderbolt. > > > > > > > > > > > > > > New SD Express card has dual mode. One is SD mode and another > > > > > > > is PCIe > > > > > > mode. > > > > > > > In PCIe mode, it act as a PCIe device and use PCIe protocol > > > > > > > not Thunderbolt > > > > > > protocol. > > > > > > > > > > > > I think what Christoph was asking about is why you need to issue > > > > > > any commands at all in SD mode when you want to use PCIe mode > > instead. > > > > > > What happens if you load the NVMe dthriver before loading the > > > > > > rts5261 > > > > driver? > > > > > > > > > > > > Arnd > > > > > > > > > > > > ------Please consider the environment before printing this e-mail. > > > > > > > > > > RTS5261 support SD mode and PCIe/NVMe mode. The workflow is as > > follows. > > > > > 1.RTS5261 work in SD mode. > > > > > 2.If card is plugged in, Host send CMD8 to ask card's PCIe availability. > > > > > > > > This sounds like the card insert/removal needs to be managed by the > > > > rtsx_pci_sdmmc driver (mmc). > > > > > > > > > 3.If the card has PCIe availability, RTS5261 switch to PCIe/NVMe mode. > > > > > > > > This switch is done by the mmc driver, but how does the PCIe/NVMe > > > > driver know when to take over? Isn't there a synchronization point needed? > > > > > > > > > 4.Mmc driver exit and NVMe driver start working. > > > > > > > > Having the mmc driver to exit seems wrong to me. Else how would you > > > > handle a card being removed and inserted again? > > > > > > > > In principle you want the mmc core to fail to detect the card and > > > > then do a handover, somehow. No? > > > > > > > > Although, to make this work there are a couple of problems you need > > > > to deal with. > > > > > > > > 1. If the mmc core doesn't successfully detect a card, it will > > > > request the mmc host to power off the card. In this situation, you > > > > want to keep the power to the card, but leave it to be managed by the > > PCIe/NVMe driver in some way. > > > > > > > > 2. During system resume, the mmc core may try to restore power for a > > > > card, especially if it's a removable slot, as to make sure it gets > > > > detected if someone inserted a card while the system was suspended. > > > > Not sure if this plays well with the PCIe/NVMe driver's behaviour. > > > > Again, I think some kind of synchronization is needed. > > > > > > > > > 5.If card is unplugged, RTS5261 will switch to SD mode. > > > > > > > > Alright, clearly the mmc driver is needed to manage card insert/removal. > > > > > > > > > We should send CMD8 in SD mode to ask card's PCIe availability, > > > > > and the > > > > order of NVMe driver and rts5261 driver doesn't matter. > > > > > > > > That assumes there's another synchronization mechanism. Maybe there > > > > is, but I don't understand how. > > > > > > > If no card in RTS5261, RTS5261 works in SD mode. If you run command lspci, > > you can see the RTS5261 device. > > > > Right. > > > > The rtsx_pci_driver (drivers/misc/cardreader/rtsx_pcr.c) has registered itself > > as a pci driver and been probed successfully, I assume. Then during > > rtsx_pci_probe() an mfd device is added via mfd_add_devices(), which > > corresponds to the rtsx_pci_sdmmc > > (drivers/mmc/host/rtsx_pci_sdmmc.c) platform driver. > > > > > When insert a SD Express card, Mmc driver will send CMD8 to ask the > > > card's PCIe availability, because it's a SD EXPRESS card, > > > > Okay, so this will then be a part of the rtsx_pci_sdmmc driver's probe sequence. > > Or more exactly, when rtsx_pci_sdmmc_drv_probe() completes successfully, a > > mmc rescan work becomes scheduled to try to detect an SD/MMC card. Then > > the CMD8 command is sent... > > > > > RTS5261 will switch to NVMe mode, after switch if you run lspci, you can see > > RTS5261 disappeared and a NVMe device replaces RTS5261. > > > > Can you elaborate more exactly how this managed? > > > > It kind of sounds like the original PCI device is being deleted? How is this > > managed? > > > > In any case, the rtsx_pci_driver's ->remove() callback, rtsx_pci_remove(), > > should be invoked, I assume? > > > > That would then lead to that mfd_remove_devices() gets called, which makes > > the ->remove() callback of the rtsx_pci_sdmmc driver, > > rtsx_pci_sdmmc_drv_remove(), to be invoked. Correct? > > > Yes, after RTS5261 switch to NVMe mode, rtsx_pci_remove() and rtsx_pci_sdmmc_drv_remove() will be invoked. So, the ->remove() callbacks are invoked because the PCI device that corresponds to the rtsx_pci_driver is being deleted. Can you explain who deletes the PCI device and why? I am not a PCI expert, so apologize for my ignorance - but I really want to understand how this is supposed to work. > > > > In NVMe mode, RTS5261 only provide a bridge between SD Express card and > > PCIe. For NVMe driver, just like a new NVMe device is inserted. > > > > I don't understand what that means, but I am also not an expert on PCI/NVMe. > > Care to explain more? > > > In NVMe mode, SD Express card connect the computer via PCIe. > IN SD mode, card connect computer via reader. That didn't make better sense to me, sorry. I do know about the SD spec and the SD-express card protocol parts. Anyway, let's leave this for now. > > > > Mmc core doesn't successfully detect the card and handover to NVMe > > > driver. Because of detect the card failed, > > > > How do you make sure that the rtsx_pci_sdmmc driver is leaving the card in the > > correct state for NVMe? > > > > For example, the mmc core has a loop re-trying with a lower initialization > > frequency for the card (400KHz, 300KHz, 200KHz, 100KHz). This will cause > > additional requests to the rtsx_pci_sdmmc driver. > > > > > Mmc driver will request the RTS5261 to power off the card, but at that time > > power off the card will not succeed. > > > > Yes, assuming no card was found, the mmc core calls mmc_power_off(). > > Ths leads to the rtsx_pci_sdmmc driver's ->set_ios() callback being invoked, > > requesting the card to be powered off. I don't see how you are managing this, > > what am I missing? > > > Before power off card and re-trying initialization, rtsx driver sets RTS5261 0xFF55 bit4=0. > After set 0xFF55 bit4=0, RTS5261 can't receive any CMD from PCIe and prepare for device disappear. > Therefore, MMC driver can't change card status. Okay, so beyond that point - any calls to the interface that is provided from drivers/misc/cardreader/rtsx_pcr will fail, when invoked by the rtsx_pci_sdmmc driver? To me, that sounds a bit fragile and it's also relying on a specific behaviour of the RTS5261 card reader interface. I wonder if this could be considered as a common behaviour...?? Perhaps it's better to teach the mmc core *more* about SD express cards. Maybe add a new host ops for dealing with the specific CMD8 command and make the mmc core to "bail out", rather than keep retrying the initialization. In principle I think the core should accept that it may have found an SD express card, then abort further communication with it. At least until the mmc host indicates that a re-initialization of the card can be done, which could be through a remove/re-probe, for example. > > > As stated above, I assume you the corresponding platform device for > > rtsx_pci_sdmmc being deleted and thus triggering the > > rtsx_pci_sdmmc_drv_remove() being called. Correct? If not, how does the > > driver manage this? > > > Yes. > > > > When the card is unplugged, RTS5261 will switch to SD mode by itself > > > and don't need mmc driver to do anything, > > > > Okay. > > > > So that means the rtsx_pci_sdmmc driver is being probed again? > > > Yes. > > > > If you run lspci, you can see NVMe device disappeared and RTS5261 appeared > > again. > > > > I see. > > If you need some help on the mmc core parts, I am willing to help out. However, first, I would like to get some better understanding of who and why the PCI device is deleted. Kind regards Uffe
