On 30 August 2017 at 14:44, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > Hi, > > > On 21-07-17 16:35, Quentin Schulz wrote: >> >> From: Hans de Goede <hdegoede@xxxxxxxxxx> >> >> Some sdio devices have a multiple stage bring-up process. Specifically >> the esp8089 (for which an out of tree driver is available) loads firmware >> on the first call to its sdio-drivers' probe function and then resets >> the device causing it to reboot from its RAM with the new firmware. >> >> When this sdio device reboots it comes back up in 1 bit 400 KHz mode >> again, and we need to walk through the whole ios negatiation and sdio >> setup >> again. >> >> There are 2 problems with this: >> >> 1) Typically these devices are soldered onto some (ARM) tablet / SBC >> PCB and as such are described in devicetree as "non-removable", which >> causes the mmc-core to scan them only once and not poll for the device >> dropping of the bus. Normally this is the right thing todo but in the >> eso8089 example we need the mmc-core to notice the module has disconnected >> (since it is now in 1 bit mode again it will not talk to the host in 4 bit >> mode). This can be worked around by using "broken-cd" in devicetree >> instead of "non-removable", but that is not a proper fix since the device >> really is non-removable. >> >> 2) When the mmc-core detects the device has disconnected it will poweroff >> the device, causing the RAM loaded firmware to be lost. This can be worked >> around in devicetree by using regulator-always-on (and avoiding the use of >> mmc-pwrseq), but again that is more of a hack then a proper fix. >> >> This commmit fixes 1) by adding a mmc_force_detect_change function which >> will cause scanning for device removal / insertion until a new device is >> detected. 2) Is fixed by a keep_power flag to the mmc_force_detect_change >> function which when set causes the mmc-core to keep the power to the >> device >> on during the rescan. >> >> Cc: Icenowy Zheng <icenowy@xxxxxxxx> >> Cc: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> >> Cc: Chen-Yu Tsai <wens@xxxxxxxx> >> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > > > So when I posted this patch quite a while back, there was some discussion > about this and a consensus that this is not the right solution. > > So first of all lets describe the problem: > > The esp8089 sdio wifi chip is really an ARM core with a wifi phy > connected to it (as many wifi chipsets are). > > But this one comes up in some really generic sdio capable boot-loader > mode and we need to feed it firmware and then reboot it into the > new firmware. > > The reboot is where the problems happens. It seems to fallback > from the negotiated 4 wire sdio mode to single wire spi mode then. > > The out of tree version of the driver deals with this by not setting > the non-removable flag as well as setting the broken_cd flag so that > the mmc core polls the device, after the reboot the poll fails > because the mmc-controller and the esp8089 are using a different > amount of wires so the mmc-cmd the poll uses times out. > > After which the esp8089 drivers remove function gets called, and > the mmc stack re-discovers the esp8089 by restarting the whole > number of wires (and speed) used negotiation. After which the > esp8089 driver's probe function gets called (again) and on > firmware loading is has set a global flag, so now it actually > acts as a wifi driver rather then trying to load the firmware > a second time. > > Since I did not want to rely on broken_cd polling I came up > with the hack which is this patch. > > So when this patch was first discussed we came to the conclusion > that what we really need is some sort of mmc_reprobe_device > function which the driver can call from probe which will > redo the number of wires (and speed) used negotiation, > while keeping the sdio_function device as is so that probe can > simply continue after this and we also don't need the ugly > global flag. > > The idea would be for this function to be some wrapper > around mmc_init_card() which resets the ios settings as is > normally done on remove and then call mmc_init_card() > passing in the existing card the same way as is done > one resume, so that the existing card / sdio_function > devices get reused. > > IIRC Ulf would look into writing this mmc_reprobe_device > function and then I would test it with the esp8089, but > Ulf never got around to writing the function and I ended > up working on other things too. Thanks for summary! Just to let you know, I haven't forgot about this problem. I am planning for a major update of the SDIO for power management support, within a not too far future. The issue described above, is then also one of the things I also plan to look into. However, if there anybody that wants to hack on this, feel free to do it! Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
