Re: [PATCH v7 2/3] mtd: rawnand: Enable monolithic read when reading subpages

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Keguang Zhang via B4 Relay <devnull+keguang.zhang.gmail.com@kernel.org>
Cc: keguang.zhang@gmail.com, Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-mips@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH v7 2/3] mtd: rawnand: Enable monolithic read when reading subpages
Date: Mon, 6 May 2024 09:17:48 +0200	[thread overview]
Message-ID: <20240506091748.18c120d5@xps-13> (raw)
In-Reply-To: <20240430-loongson1-nand-v7-2-60787c314fa4@gmail.com>

Hi,

devnull+keguang.zhang.gmail.com@kernel.org wrote on Tue, 30 Apr 2024
19:11:11 +0800:

> From: Keguang Zhang <keguang.zhang@gmail.com>
> 
> nand_read_subpage() reads data and ECC data by two separate
> operations.
> This patch allows the NAND controllers who support
> monolithic page read to do subpage read by a single operation,
> which is more effective than nand_read_subpage().

I am a bit puzzled by this change. Usually nand_read_subpage is used
for optimizations (when less data than a full page must be retrieved).
I know it may be used in other cases (because it's easier for the core
in order to support a wide range of controllers). Can you please show a
speed test showing the results before I consider merging this patch?

The monolithic thing was not supposed to improve throughput but to help
with very limited controllers.

Thanks,
Miquèl