From: Fabio Estevam <festevam@gmail.com>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Dong Aisheng <aisheng.dong@freescale.com>,
Kevin Lemoi <kevin.lemoi@savant.com>,
Otavio Salvador <otavio@ossystems.com.br>,
Sascha Hauer <kernel@pengutronix.de>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
"Dong, Chuanxiao" <chuanxiao.dong@intel.com>,
linux-mmc <linux-mmc@vger.kernel.org>,
Fabio Estevam <fabio.estevam@freescale.com>
Subject: Re: [PATCH v2] mmc: core: Do not set mmc voltage to 1.8V when 'no-1-8-v' is present
Date: Wed, 17 Jun 2015 13:25:21 -0300 [thread overview]
Message-ID: <CAOMZO5Aq-aTjQ1rddBJcrJ56jRV1Q=dLgK5j4TasKdykiWLniQ@mail.gmail.com> (raw)
In-Reply-To: <CAPDyKFotVdm5vDwjqUw=cD9jmRU86ZBbq1c-qmiFa4Yj2JivxQ@mail.gmail.com>
Hi Ulf,
On Tue, Jun 16, 2015 at 6:31 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> I had a closer look, should have done that before.
>
> I think we need to decide what "no-1-8-v" should be used for.
> Currently the DT documentation is unclear and depending on what SDHCI
> variant, the binding has different purpose. It's a mess!
Thanks for your feedback.
>
> sdhci-pltfm + sdhci-esdhc-imx use the "no-1-8-v" DT binding to enable
> the SDHCI_QUIRK2_NO_1_8_V. The sdhci driver uses this quirk to mask
> the bus speed modes for SD UHS cards.
>
> In this regards, consider the two below options.
>
> 1) We have DT bindings for SD UHS speed modes, which somehow makes the
> "no-1-8-v" binding redundant (or deprecated).
>
> 2) If you can model the VCCQ power supply as as a regulator, you could
> use regulator_is_supported_voltage() API to find out similar
> information used to set SDHCI_QUIRK2_NO_1_8_V. In fact, sdhci already
> does that to mask MMC_CAP2_HSX00_1_2V, unless 1.2V is supported.
>
> In a third case, sdhci-pxav3 use the "no-1-8-v" DT binding to mask
> SDHCI_CAN_VDD_180/SDHCI_CAN_VDD_330, which seems wrong, as it has
> nothing to do with the power to the card (VMMC). It's also used it to
> mask MMC_CAP_1_8V_DDR.
>
> The summary, is that I would rather see us to move away from using the
> "no-1-8-v" DT binding and use the proper SD UHS bus speed modes
> binding instead.
Makes sense indeed.
The challenge here is that we still need to keep the old dtb's working.
Motivation for this patch was a custom mx6sl board that works fine
with 3.14, but after upgrading the kernel to 4.0 the eMMC no longer
can mount the rootfs. This is a regression caused by commit
312449efd16bb06, which applies 1.8V to the eMMC card that can only
operate at 3.3V.
Same thing happens on imx6q-sabresd: we have 3.3V voltage being
supplied to the eMMC, but now we are operating it at 1.8V, even though
if we have 'no-1-8-v' property in the device tree.
While I understand the need for improvement that you clearly
described, I would also like that the old dtb's could still work
'as-is' with a modern kernel.
The path I propose here was the minimal invasive method I could come
up to allow the old dtb compatibility.
Thanks,
Fabio Estevam
next prev parent reply other threads:[~2015-06-17 16:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-13 20:24 [PATCH v2] mmc: core: Do not set mmc voltage to 1.8V when 'no-1-8-v' is present Fabio Estevam
2015-06-15 11:44 ` Otavio Salvador
2015-06-15 12:08 ` Ulf Hansson
2015-06-15 12:23 ` Fabio Estevam
2015-06-15 12:49 ` Fabio Estevam
2015-06-16 9:31 ` Ulf Hansson
2015-06-17 16:25 ` Fabio Estevam [this message]
2015-06-18 7:58 ` Ulf Hansson
2015-06-18 14:25 ` Dong Aisheng
2015-06-18 14:03 ` Dong Aisheng
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