> -----Original Message----- > From: Stefan Agner [mailto:stefan@xxxxxxxx] > Sent: Wednesday, July 4, 2018 11:08 PM > To: adrian.hunter@xxxxxxxxx; ulf.hansson@xxxxxxxxxx > Cc: Fabio Estevam <fabio.estevam@xxxxxxx>; Bough Chen > <haibo.chen@xxxxxxx>; A.s. Dong <aisheng.dong@xxxxxxx>; > michael@xxxxxxxxxxxxxxxxxxxx; rmk+kernel@xxxxxxxxxxxxxxx; linux- > mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Stefan Agner > <stefan@xxxxxxxx> > Subject: [PATCH v2] mmc: sdhci-esdhc-imx: allow 1.8V modes without > 100/200MHz pinctrl states > > 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 > >From current code, the NO_1_8_V quirk seems like only affect sd card. The 1.8v timing is still allowed for eMMC 1_8V DDR. See below: if ((mmc->caps & (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 | MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 | MMC_CAP_UHS_DDR50 | MMC_CAP_1_8V_DDR)) || (mmc->caps2 & (MMC_CAP2_HS200_1_8V_SDR | MMC_CAP2_HS400_1_8V))) host->flags |= SDHCI_SIGNALING_180; Due to i have no board to try that case, can you please help detail more on how the eMMC DDR52 is blocked due to that quirk? Regards Dong Aisheng > 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: > https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flkml > .kernel.org%2Fr%2F20180628081331.13051-1- > stefan%40agner.ch&data=02%7C01%7Caisheng.dong%40nxp.com%7Ca > 32bdbdb4e854ed1a49008d5e1bfeae2%7C686ea1d3bc2b4c6fa92cd99c5c30163 > 5%7C0%7C0%7C636663136759720275&sdata=%2F2gJ%2BA0fHCzzUehD7 > 9knsfy3WMj4Okp%2BcxXB70MI5y8%3D&reserved=0 > Signed-off-by: Stefan Agner <stefan@xxxxxxxx> > --- > drivers/mmc/host/sdhci-esdhc-imx.c | 21 +++++++++------------ > 1 file changed, 9 insertions(+), 12 deletions(-) > > diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci- > esdhc-imx.c > index 20a420b765b3..e96d969ab2c3 100644 > --- a/drivers/mmc/host/sdhci-esdhc-imx.c > +++ b/drivers/mmc/host/sdhci-esdhc-imx.c > @@ -312,6 +312,15 @@ static u32 esdhc_readl_le(struct sdhci_host *host, > int reg) > > if (imx_data->socdata->flags & ESDHC_FLAG_HS400) > val |= SDHCI_SUPPORT_HS400; > + > + /* > + * Do not advertise faster UHS modes if there are no > + * pinctrl states for 100MHz/200MHz. > + */ > + if (IS_ERR_OR_NULL(imx_data->pins_100mhz) || > + IS_ERR_OR_NULL(imx_data->pins_200mhz)) > + val &= ~(SDHCI_SUPPORT_SDR50 | > SDHCI_SUPPORT_DDR50 > + | SDHCI_SUPPORT_SDR104 | > SDHCI_SUPPORT_HS400); > } > } > > @@ -1157,18 +1166,6 @@ sdhci_esdhc_imx_probe_dt(struct > platform_device *pdev, > > ESDHC_PINCTRL_STATE_100MHZ); > imx_data->pins_200mhz = pinctrl_lookup_state(imx_data- > >pinctrl, > > ESDHC_PINCTRL_STATE_200MHZ); > - if (IS_ERR(imx_data->pins_100mhz) || > - IS_ERR(imx_data->pins_200mhz)) { > - dev_warn(mmc_dev(host->mmc), > - "could not get ultra high speed state, work on > normal mode\n"); > - /* > - * fall back to not supporting uhs by specifying no > - * 1.8v quirk > - */ > - host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V; > - } > - } else { > - host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V; > } > > /* call to generic mmc_of_parse to support additional capabilities */ > -- > 2.18.0 -- 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
