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SubjectRE: [PATCH v2] mmc: sdhci-esdhc-imx: allow 1.8V modes without 100/200MHz pinctrl states
Date
> -----Original Message-----
> From: Stefan Agner [mailto:stefan@agner.ch]
> Sent: Wednesday, July 4, 2018 11:08 PM
> To: adrian.hunter@intel.com; ulf.hansson@linaro.org
> Cc: Fabio Estevam <fabio.estevam@nxp.com>; Bough Chen
> <haibo.chen@nxp.com>; A.s. Dong <aisheng.dong@nxp.com>;
> michael@amarulasolutions.com; rmk+kernel@armlinux.org.uk; linux-
> mmc@vger.kernel.org; linux-kernel@vger.kernel.org; Stefan Agner
> <stefan@agner.ch>
> 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&amp;data=02%7C01%7Caisheng.dong%40nxp.com%7Ca
> 32bdbdb4e854ed1a49008d5e1bfeae2%7C686ea1d3bc2b4c6fa92cd99c5c30163
> 5%7C0%7C0%7C636663136759720275&amp;sdata=%2F2gJ%2BA0fHCzzUehD7
> 9knsfy3WMj4Okp%2BcxXB70MI5y8%3D&amp;reserved=0
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
> 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

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