Hi Ulf, On Tue, Jun 16, 2015 at 6:31 AM, Ulf Hansson <ulf.hans...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
