[U-Boot] [PATCH 1/9] mmc: sdhci: Clear SDHCI_CLOCK_CONTROL before configuring the new value

[Jaehoon Chung]

On 01/19/2017 04:39 PM, Stefan Roese wrote:
> This patch completely clears the SDHCI_CLOCK_CONTROL register before the
> new value is configured instead of just clearing the 2 bits
> SDHCI_CLOCK_CARD_EN and SDHCI_CLOCK_INT_EN. Without this change, some
> clock configurations will lead to the "Internal clock never stabilised."
> error message on the Xenon SDHCI controller used on the Marvell Armada
> 3700 and 7k/8k ARM64 SoCs.
> 
> The Linux SDHCI core driver also writes 0 to this register before
> the new value is configured. So this patch simplifies the driver a bit
> and brings the U-Boot driver more in-line with the Linux one.
> 
> Signed-off-by: Stefan Roese <sr at denx.de>
> Cc: Jaehoon Chung <jh80.chung at samsung.com>
> Cc: Siva Durga Prasad Paladugu <sivadur at xilinx.com>
> Cc: Michal Simek <michal.simek at xilinx.com>

Reviewed-by: Jaehoon Chung <jh80.chung at samsung.com>

> ---
>  drivers/mmc/sdhci.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mmc/sdhci.c b/drivers/mmc/sdhci.c
> index 5b404ff4a3..081b014a17 100644
> --- a/drivers/mmc/sdhci.c
> +++ b/drivers/mmc/sdhci.c
> @@ -295,7 +295,7 @@ static int sdhci_send_command(struct mmc *mmc, struct mmc_cmd *cmd,
>  static int sdhci_set_clock(struct mmc *mmc, unsigned int clock)
>  {
>  	struct sdhci_host *host = mmc->priv;
> -	unsigned int div, clk = 0, timeout, reg;
> +	unsigned int div, clk = 0, timeout;
>  
>  	/* Wait max 20 ms */
>  	timeout = 200;
> @@ -311,9 +311,7 @@ static int sdhci_set_clock(struct mmc *mmc, unsigned int clock)
>  		udelay(100);
>  	}
>  
> -	reg = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> -	reg &= ~(SDHCI_CLOCK_CARD_EN | SDHCI_CLOCK_INT_EN);
> -	sdhci_writew(host, reg, SDHCI_CLOCK_CONTROL);
> +	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>  
>  	if (clock == 0)
>  		return 0;
>