Re: [PATCH] mmc: tegra: Disable UHS-I modes for tegra30

Stephen Warren
2016-05-10T17:49:52Z

On 05/10/2016 11:16 AM, Jon Hunter wrote:
>
> On 10/05/16 17:34, Stephen Warren wrote:
>> On 05/10/2016 10:13 AM, Jon Hunter wrote:
>
> [snip]
>
>>> Stephen, for your u-boot testing, do you are set the bit in the vendor
>>> misc register to enable version 3.0 support for sdhci on tegra30? This
>>> is what the above quirk is doing (and has done so for a very long time).
>>
>> I don't see anything in the U-Boot driver that is equivalent to the
>> kernel's NVQUIRK_ENABLE_SDHCI_SPEC_300. I assume that means the
>> controller advertises an early spec version when in U-Boot, which simply
>> means U-Boot doesn't know to take advantage of any faster transfer modes
>> enabled by later specification versions, but I'm not entirely sure what
>> effect the following kernel code has on the HW:
>>
>>> /* Erratum: Enable SDHCI spec v3.00 support */
>>> if (soc_data->nvquirks & NVQUIRK_ENABLE_SDHCI_SPEC_300)
>>> misc_ctrl |= SDHCI_MISC_CTRL_ENABLE_SDHCI_SPEC_300;
>
> Do you see it touch the SDHCI_TEGRA_VENDOR_MISC_CTRL register?

Not at all. For reference, the register is defined in
arch/arm/include/asm/arch-tegra/tegra_mmc.h as venmiscctl, and that
symbol isn't referenced anywhere.