[RFT PATCH 2/2] mmc: meson-gx: set 270 core phase during the identification

[Viacheslav]

After running some tests, I've noticed inconsistent behavior with the eMMC:
 On a cold boot (following a shutdown), the eMMC operates as expected within U-Boot.
 On a hot reboot (via the kernel's reboot command), the eMMC sometimes (not always, but if
fit in error, next need to do poweroff) does not work:
    U-Boot is able to read the dtb file but won't boot kernel completely, or
    U-Boot might fail to read from the eMMC altogether.

This behavior had not occurred before (when the phase was set to 270 on axg).

On Fri, 2023-09-15 at 18:01 +0200, Jerome Brunet wrote:
> It has been reported that some devices have problems with a 180 degree
> core phase. Setting 270 helped some of these devices. Other continue to
> struggle (while it works fine with 180 in Linux ... :sigh:)
> 
> Poking around the HW, it seems that setting a 270 core phase during the
> identification, then using 180 for the rest of the operations, helps the
> device operate correctly.
> 
> Signed-off-by: Jerome Brunet <jbrunet at baylibre.com>
> ---
>  drivers/mmc/meson_gx_mmc.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/meson_gx_mmc.c b/drivers/mmc/meson_gx_mmc.c
> index c6168792cbae..284be2b9dca4 100644
> --- a/drivers/mmc/meson_gx_mmc.c
> +++ b/drivers/mmc/meson_gx_mmc.c
> @@ -54,9 +54,14 @@ static void meson_mmc_config_clock(struct mmc *mmc)
>  
>  	/* Clk always on */
>  	meson_mmc_clk |= pdata->version->clk_always_on;
> -	meson_mmc_clk |= CLK_CO_PHASE_180;
>  	meson_mmc_clk |= CLK_TX_PHASE_000;
>  
> +	/* Core phase according to mode */
> +	if (mmc->selected_mode == MMC_LEGACY)
> +		meson_mmc_clk |= CLK_CO_PHASE_270;
> +	else
> +		meson_mmc_clk |= CLK_CO_PHASE_180;
> +
>  	/* 1GHz / CLK_MAX_DIV = 15,9 MHz */
>  	if (mmc->clock > 16000000) {
>  		clk = SD_EMMC_CLKSRC_DIV2;