Re: [PATCH] ARM: rockchip: dmc: fix DRAM for sizes 16+ GiB on rk3588

[Sascha Hauer <s.hauer@pengutronix.de>]

On Fri, Apr 11, 2025 at 05:20:20PM +0200, Michael Tretter wrote:
> RK3588 has two known memory gaps when using 16+ GiB DRAM,
> [0x3fc000000, 0x3fc500000) and [0x3fff00000, 0x400000000).
> 
> Skip both gaps when initializing the DRAM on rk3588 to avoid running
> into an exception when running memtest on an rk3588 board with 16+ GiB
> DRAM.
> 
> The information about the gaps is taken from a patch by Jonas Karlman to
> the U-Boot mailing list [0].
> 
> [0] https://lore.kernel.org/all/20250405153832.1427549-5-jonas@kwiboo.se/
> 
> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
> ---
> The start and end addresses of the gaps probably should be put into of
> rockchip_dmc_drvdata and only set for the rk3588. Any suggestion how to
> implement this more nicely would be very welcome.

Looks like the rk3588 currently is the only SoC that can have that much
memory that it hits the gaps. You could add a comment that the gaps are
only verified on rk3588 and need another look once the next SoC is
added.

Once we are there we can add a function pointer into struct rockchip_dmc_drvdata
doing the right thing, but I think for now it's fine the way you did it.

Sascha

> ---
>  arch/arm/mach-rockchip/dmc.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/mach-rockchip/dmc.c b/arch/arm/mach-rockchip/dmc.c
> index 86e61f311661..cf63fdb5a8bb 100644
> --- a/arch/arm/mach-rockchip/dmc.c
> +++ b/arch/arm/mach-rockchip/dmc.c
> @@ -27,6 +27,12 @@
>  #define RK3568_INT_REG_START		RK3399_INT_REG_START
>  #define RK3588_INT_REG_START		RK3399_INT_REG_START
>  
> +/* RK3588 has two known memory gaps when using 16+ GiB DRAM */
> +#define DRAM_GAP1_START         0x3fc000000
> +#define DRAM_GAP1_END           0x3fc500000
> +#define DRAM_GAP2_START         0x3fff00000
> +#define DRAM_GAP2_END           0x400000000
> +
>  struct rockchip_dmc_drvdata {
>  	unsigned int os_reg2;
>  	unsigned int os_reg3;
> @@ -220,9 +226,19 @@ static int rockchip_dmc_probe(struct device *dev)
>  	arm_add_mem_device("ram0", membase,
>  		min_t(resource_size_t, drvdata->internal_registers_start, memsize) - membase);
>  
> -	/* ram1, remaining RAM beyond 32bit space */
> +	/* ram1, RAM beyond 32bit space up to first gap */
>  	if (memsize > SZ_4G)
> -		arm_add_mem_device("ram1", SZ_4G, memsize - SZ_4G);
> +		arm_add_mem_device("ram1", SZ_4G,
> +			min_t(resource_size_t, DRAM_GAP1_START, memsize) - SZ_4G);
> +
> +	/* ram2, RAM between first and second gap */
> +	if (memsize > DRAM_GAP1_END)
> +		arm_add_mem_device("ram2", DRAM_GAP1_END,
> +			min_t(resource_size_t, DRAM_GAP2_START, memsize) - DRAM_GAP1_END);
> +
> +	/* ram3, remaining RAM after second gap */
> +	if (memsize > DRAM_GAP2_END)
> +		arm_add_mem_device("ram3", DRAM_GAP2_END, memsize - DRAM_GAP2_END);
>  
>  	return 0;
>  }
> -- 
> 2.39.5
> 
> 
> 

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