On 05.07.2018 13:23, Ulf Hansson wrote: > On 4 July 2018 at 17:07, Stefan Agner <stefan@xxxxxxxx> wrote: >> If pinctrl nodes for 100/200MHz are missing, the controller should >> not select any mode which need signal frequencies 100MHz or higher. >> To prevent such speed modes the driver currently uses the quirk flag >> SDHCI_QUIRK2_NO_1_8_V. This works nicely for SD cards since 1.8V >> signaling is required for all faster modes and slower modes use 3.3V >> signaling only. >> >> However, there are eMMC modes which use 1.8V signaling and run below >> 100MHz, e.g. DDR52 at 1.8V. With using SDHCI_QUIRK2_NO_1_8_V this >> mode is prevented. When using a fixed 1.8V regulator as vqmmc-supply >> the stack has no valid mode to use. In this tenuous situation the >> kernel continuously prints voltage switching errors: >> mmc1: Switching to 3.3V signalling voltage failed >> >> Avoid using SDHCI_QUIRK2_NO_1_8_V and prevent faster modes by >> altering the SDHCI capability register. With that the stack is able >> to select 1.8V modes even if no faster pinctrl states are available: >> # cat /sys/kernel/debug/mmc1/ios >> ... >> timing spec: 8 (mmc DDR52) >> signal voltage: 1 (1.80 V) >> ... >> >> Link: http://lkml.kernel.org/r/20180628081331.13051-1-stefan@xxxxxxxx >> Signed-off-by: Stefan Agner <stefan@xxxxxxxx> > > I am fine with this. Do you want me to apply this for now, to get it tested? > Yes. > I guess its also material for stable and as fix? > I guess. We probably want to wait until it gets some more testing? > In regards to the printed warning, it sounds to me like a different > issue, which we can solve on top. Right? Yes different issue, which we can handle separately. -- Stefan -- 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
