[PATCH v2 1/2] Actions: OWL: Calculate SDRAM size

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

Hi Amit,

On Fri, May 08, 2020 at 03:53:45PM +0530, Amit Singh Tomar wrote:
> Calculate the SDRAM size from DDR capacity register registers instead
> of using hard-coded value. This is quite useful to get correct size
> on differnt boards based on Actions OWL family of SoCs (S700 and S900).
> 
> There is no documentation available that talks about DDR registers, and
> this is very much taken from vendor source.
> 
> This commit lets Linux boot on Cubieboard7-lite(based on S700).
> 
> Signed-off-by: Amit Singh Tomar <amittomer25@gmail.com>
> ---
> Changes since v1:
> 	* added support for S900
> 	* updated the commit message to reflect common OWL
> 	  support.
> ---
>  arch/arm/mach-owl/soc.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-owl/soc.c b/arch/arm/mach-owl/soc.c
> index 409cbd319f20..2ae357e3672a 100644
> --- a/arch/arm/mach-owl/soc.c
> +++ b/arch/arm/mach-owl/soc.c
> @@ -13,15 +13,40 @@
>  #include <asm/mach-types.h>
>  #include <asm/psci.h>
>  
> +#define DMM_INTERLEAVE_BASE             (0xe0290020)
> +#define DMM_INTERLEAVE_PER_CH_CFG       (DMM_INTERLEAVE_BASE +  0x08)
> +#define DMM_MASTER_READ_TO              (DMM_INTERLEAVE_BASE +  0x48)
> +
>  DECLARE_GLOBAL_DATA_PTR;
>  
> +unsigned int get_owl_ram_size(void)
> +{
> +	__maybe_unused unsigned int val, cap, channel, channel_num;
> +
> +	/* ddr capacity register initialized by ddr driver
> +	 * in early bootloader
> +	 */
> +#if defined(CONFIG_MACH_S700)
> +	val = (readl(DMM_INTERLEAVE_PER_CH_CFG) >> 8) & 0x7;
> +	cap =  (val + 1) * 256;
> +#elif defined(CONFIG_MACH_S900)
> +	chennel_num = (readl(DMM_INTERLEAVE_BASE) >> 24) & 0xf;
> +	channel = (ch_num >= 3) ? 1 : 0;
> +	val = (readl(DMM_MASTER_READ_TO)) & 0xf;
> +	cap = ((val + 1) << channel) * 256;

This doesn't work on Bubblegum96. But poking into the vendor tree, I'm able
to come up with below working code:

        val = (readl(DMM_INTERLEAVE_PER_CH_CFG) >> 8) & 0xf;
        cap =  64 * (1 << val);

So, you can use this and remove other stuffs. Also this function should be named
as owl_get_ddr_cap().

Thanks,
Mani

> +#endif
> +
> +	return cap;
> +}
> +
>  /*
>   * dram_init - sets uboots idea of sdram size
>   */
>  int dram_init(void)
>  {
> -	gd->ram_size = CONFIG_SYS_SDRAM_SIZE;
> +	gd->ram_size = get_owl_ram_size() * 1024 * 1024;
>  	return 0;
> +
>  }
>  
>  /* This is called after dram_init() so use get_ram_size result */
> -- 
> 2.7.4
>