linux-kernel - Re: [PATCH v2 2/5] spi: spi-ti-qspi: add mmap mode read support

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Date:	Wed, 4 Nov 2015 14:41:12 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Vignesh R <vigneshr@...com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Michal Suchanek <hramrach@...il.com>,
	Russell King <linux@....linux.org.uk>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org
Subject: Re: [PATCH v2 2/5] spi: spi-ti-qspi: add mmap mode read support

On Tue, Nov 03, 2015 at 03:36:11PM +0530, Vignesh R wrote:

> +	ti_qspi_enable_memory_map(spi);
> +	ti_qspi_setup_mmap_read(spi, read_opcode, addr_width,
> +				dummy_bytes);
> +	memcpy_fromio(buf, qspi->mmap_base + from, len);
> +	*retlen = len;
> +	ti_qspi_disable_memory_map(spi);

We'll be constantly enabling and disabling memory mapping with this.
I'm not sure that's a meaningful cost given that it doesn't actually
remap anything but rather just switches hardware modes, we can always
optimise it later if it is.

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