linux-kernel - Re: [PATCH 1/2] spi/rockchip: fix bug that case spi can't go as fast as slave request

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Message-ID: <20141016102636.GE2200@sirena.org.uk>
Date:	Thu, 16 Oct 2014 12:26:36 +0200
From:	Mark Brown <broonie@...nel.org>
To:	addy ke <addy.ke@...k-chips.com>
Cc:	heiko@...ech.de, dianders@...omium.org, grant.likely@...aro.org,
	robh+dt@...nel.org, amstan@...gle.com, sonnyrao@...gle.com,
	linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
	olof@...om.net, hj@...k-chips.com, kever.yang@...k-chips.com,
	xjq@...k-chips.com, huangtao@...k-chips.com, zyw@...k-chips.com,
	yzq@...k-chips.com, zhenfu.fang@...k-chips.com, cf@...k-chips.com,
	zhangqing@...k-chips.com, hl@...k-chips.com, wei.luo@...k-chips.com
Subject: Re: [PATCH 1/2] spi/rockchip: fix bug that case spi can't go as fast
 as slave request

On Thu, Oct 16, 2014 at 05:58:51PM +0800, addy ke wrote:

Please fix your mailer to word wrap within paragraphs.

> On 2014/10/16 17:34, Mark Brown wrote:

> >> If we set the rate unconditionally here, clk_set_rate() will be executed in each spi transfer.

> > Is that really such a high cost?

> Not high cost, but  I think if the default spi_clk is enough, we do not need to set spi_clk again.

> Maybe we can only set spi_clk as (2 * MAX_SCLK_OUT) in probe().

It's not too bad to do it where it is, it just seems better to be
simpler.

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