[RFC 1/2] rockchip: sdram: Allow board/soc specific RAM bank logic

[Chris Morgan]

On Sat, Mar 30, 2024 at 12:00:46PM +0100, Jonas Karlman wrote:
> Hi Chris,
> 
> On 2024-03-30 06:05, Chris Morgan wrote:
> > From: Chris Morgan <macromorgan at hotmail.com>
> > 
> > Allow individual boards or SoCs to alter the RAM bank addition logic
> > by defining a __weak function that these boards can then override
> > if needed. In the event this function fails, fallback to the default
> > detection logic.
> > 
> > Signed-off-by: Chris Morgan <macromorgan at hotmail.com>
> > ---
> >  arch/arm/mach-rockchip/sdram.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/arch/arm/mach-rockchip/sdram.c b/arch/arm/mach-rockchip/sdram.c
> > index 0d9a0aef6f..53aa19feca 100644
> > --- a/arch/arm/mach-rockchip/sdram.c
> > +++ b/arch/arm/mach-rockchip/sdram.c
> > @@ -35,11 +35,18 @@ struct tos_parameter_t {
> >  	s64 reserve[8];
> >  };
> >  
> > +__weak int rk_get_ram_banks(void)
> 
> I would call this rockchip_dram_init_banksize()
> 
> > +{
> > +	return -EINVAL;
> 
> and return 0 in default implementation,
> 
> > +}
> > +
> >  int dram_init_banksize(void)
> >  {
> >  	size_t ram_top = (unsigned long)(gd->ram_size + CFG_SYS_SDRAM_BASE);
> >  	size_t top = min((unsigned long)ram_top, (unsigned long)(gd->ram_top));
> >  
> > +	if (!rk_get_ram_banks())
> > +		return 0;
> 
> and something like:
> 
> ret = rockchip_dram_init_banksize();
> if (ret)
> 	return ret;
> 
> is probably a better pattern when allowing board specific weak
> implementations.

Thank you for the input, I'll find a way to refactor it where we
return 0 on success, return < 0 on failure, and return > 0 on
success. Then we can just check for values > 0 to skip the
fallback code.

Chris

> 
> Regards,
> Jonas
> 
> >  #ifdef CONFIG_ARM64
> >  	/* Reserve 0x200000 for ATF bl31 */
> >  	gd->bd->bi_dram[0].start = 0x200000;
>