[U-Boot] u-boot on Minnowboard max

[Bin Meng]

Hi,

On Tue, Jun 7, 2016 at 2:09 PM, vinoth eswaran <evinoth1206 at gmail.com> wrote:
> Hello Mr.Bin,
>

Please keep the ML in the loop, also avoid top-posting, and always use
plain text.

>  I have attached the start up logs for your reference, I have added some
> debug messages also and I have disabled the SDIO (0f15) by removing it from
> u-boot , so please ignore that.
>
> bootcmd=fatload mmc 0:1 01000000 bzImage; zboot 01000000
>
> I am not passing any commnd line from u-boot.
>
> Since I have builded a customised Linux kernel I have the command line added
> in one of the .scc files.
>
> Kernel command line: root=/dev/mmcblk0p2 rootwait rootfstype=ext4
> console=ttyS0,115200 console=tty0
>
> My View:
>
> By UEFI SDHCI is on ACPI
>
>  mmc0: SDHCI controller on ACPI [80860F16:00] using ADMA
>
> and by u-boot SDHCI is on PCI
>
>  mmc0: SDHCI controller on PCI [0000:00:12.0] using ADMA
>
> and I think that something is missing in U-boot or Linux , so it is unable
> to initialize SD card. It will be great , if u give me some inputs to fix
> this issue.
>

Just some initial investigation based on your log. It looks Linux kernel prints:

[    1.267312] sdhci-pci 0000:00:12.0: failed to setup card detect gpio

where it calls mmc_gpiod_request_cd() in drivers/mmc/host/sdhci-pci-core.c:

mmc_gpiod_request_cd(host->mmc, slot->cd_con_id, slot->cd_idx,
                                 slot->cd_override_level, 0, NULL)) {
                dev_warn(&pdev->dev, "failed to setup card detect gpio\n");
                slot->cd_idx = -1;
        }

I did not have time to debug this, but based on the API name it looks
to me this mmc_gpiod_request_cd() has something to do with GPIO where
the Linux SDHC driver requests a card detect signal from a GPIO pin.

On BayTrail, GPIO driver in Linux only works with ACPI as it cannot be
discovered via PCI, so U-Boot must ship with an ACPI table, which is
already supported in the latest mainline. Please do the same testing
with the latest U-Boot to see if the problem still exists.

Regards,
Bin