[U-Boot] [PATCH 1/4] mmc: meson-gx: Fix tx phase in the tuning process

[Anand Moon]

Hi Jerome / Neil,

[...]
>
> I'm not quite sure I get what I should understand from this log.
>
> I can comment on the original patch though.
>
> I think you should keep the phase settings aligned with Linux.
>

Thanks for this inputs.
> A) Among the exchange I had with amlogic, I got that there should always
> be a phase shift of 180 degree between the core and Tx phase.
>
> B) So far, Core=180, Tx=0, Rx=0 has proven to be quite stable for all
> the devices. I spent significant amount of time testing that.
>

I feel you are referring below in mainline kernel

#define   CLK_CORE_PHASE_MASK GENMASK(9, 8)
#define   CLK_TX_PHASE_MASK GENMASK(11, 10)
#define   CLK_RX_PHASE_MASK GENMASK(13, 12)

        /* init SD_EMMC_CLOCK to sane defaults w/min clock rate */
        clk_reg = CLK_ALWAYS_ON(host);
        clk_reg |= CLK_DIV_MASK;
        clk_reg |= FIELD_PREP(CLK_CORE_PHASE_MASK, CLK_PHASE_180);
        clk_reg |= FIELD_PREP(CLK_TX_PHASE_MASK, CLK_PHASE_0);
        clk_reg |= FIELD_PREP(CLK_RX_PHASE_MASK, CLK_PHASE_0);
        writel(clk_reg, host->regs + SD_EMMC_CLOCK);

So in the current u-boot host we are not setting the correct bits for
clock tuning

I have modified with above changes and was able to boot into my Odorid
N2 on emmc.
I will check this out on my Odroid C2 and sdcard and then submit the
next version.

> If that's not the case for the N2 under linux, please report it to the
> related ML. If these settings works under Linux, then it is not the
> problem and I don't think you should change them in u-boot.

----
clock is enabled (380953Hz)
clock is enabled (25000000Hz)
clock is enabled (52000000Hz)
switch to partitions #0, OK
mmc2(part 0) is current device
Scanning mmc 2:1...
Found U-Boot script /boot/boot.scr
745 bytes read in 1 ms (727.5 KiB/s)
## Executing script at 08000000
27445760 bytes read in 605 ms (43.3 MiB/s)
65829 bytes read in 3 ms (20.9 MiB/s)
7404738 bytes read in 164 ms (43.1 MiB/s)
## Flattened Device Tree blob at 08008000

-Anand