Re: [PATCH v8 07/20] mailbox: mtk-cmdq: Add mminfra_offset configuration for DRAM transaction

[AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>]

Il 17/10/25 08:44, Jason-JH Lin ha scritto:
> The GCE in MT8196 is placed in MMINFRA and requires all addresses
> in GCE instructions for DRAM transactions to be IOVA.
> 
> Due to MMIO, if the GCE needs to access a hardware register at
> 0x1000_0000, but the SMMU is also mapping a DRAM block at 0x1000_0000,
> the MMINFRA will not know whether to write to the hardware register or
> the DRAM.
> To solve this, MMINFRA treats addresses greater than 2G as data paths
> and those less than 2G as config paths because the DRAM start address
> is currently at 2G (0x8000_0000). On the data path, MMINFRA remaps
> DRAM addresses by subtracting 2G, allowing SMMU to map DRAM addresses
> less than 2G.
> For example, if the DRAM start address 0x8000_0000 is mapped to
> IOVA=0x0, when GCE accesses IOVA=0x0, it must add a 2G offset to
> the address in the GCE instruction. MMINFRA will then see it as a
> data path (IOVA >= 2G) and subtract 2G, allowing GCE to access IOVA=0x0.
> 
> Since the MMINFRA remap subtracting 2G is done in hardware and cannot
> be configured by software, the address of DRAM in GCE instruction must
> always add 2G to ensure proper access. After that, the shift functions
> do more than just shift addresses, so the APIs were renamed to
> cmdq_convert_gce_addr() and cmdq_revert_gce_addr().
> 
> This 2G adjustment is referred to as mminfra_offset in the CMDQ driver.
> CMDQ helper can get the mminfra_offset from the cmdq_mbox_priv of
> cmdq_pkt and add the mminfra_offset to the DRAM address in GCE
> instructions.
> 
> Signed-off-by: Jason-JH Lin <jason-jh.lin@mediatek.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>