Re: [PATCH v11 2/2] mtd: rawnand: Add Loongson-1 NAND Controller Driver

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Keguang Zhang <keguang.zhang@gmail.com>
Cc: Keguang Zhang via B4 Relay
	<devnull+keguang.zhang.gmail.com@kernel.org>,
	Richard Weinberger <richard@nod.at>,
	 Vignesh Raghavendra <vigneshr@ti.com>,
	 Rob Herring <robh@kernel.org>,
	 Krzysztof Kozlowski <krzk+dt@kernel.org>,
	 Conor Dooley <conor+dt@kernel.org>,
	linux-mtd@lists.infradead.org,  linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org,  linux-media@vger.kernel.org
Subject: Re: [PATCH v11 2/2] mtd: rawnand: Add Loongson-1 NAND Controller Driver
Date: Mon, 20 Jan 2025 09:10:04 +0100	[thread overview]
Message-ID: <874j1tykgz.fsf@bootlin.com> (raw)
In-Reply-To: <CAJhJPsVhH=8dKmUgmTSHnG8H1_9G3zvovX9hDv_VM6fSUR5oQw@mail.gmail.com> (Keguang Zhang's message of "Sat, 18 Jan 2025 16:01:19 +0800")

>> >> Don't you need a dma_addr_t here instead? You shall remap the resource.
>> >>
>> > Sorry, I don't quite understand.
>> > 'dma_base' is already of type dma_addr_t.
>>
>> I didn't identify where the dma_base was remapped, but if that's already
>> done then we're good.
>
> Perhaps I misunderstand the usage of dma_map_resource(). dma_base is
> the physical address and will be written to the DMA controller
> register at last.

IIUC, yes and no. It is the remapped address of the physical address you
want to reach, not the physical address itself. The type is dma_addr_t
and not phys_addr_t and you can get a dma address out of a physical
address with a call to dma_map_resource(). The numerical value might be
the same if there is no IO-MMU involved, but the good practice is to
remap anyway.

Thanks,
Miquèl

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