linux-kernel - Re: [PATCH 2/2] spi/rockchip: Add device tree property to configure Rx Sample Delay

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Message-ID: <CAD=FV=VjTK2fvBnZwrLXuqVSMZC4CD3NFEykUxbt1-LV_MgQRA@mail.gmail.com>
Date:	Thu, 26 Mar 2015 17:29:24 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Julius Werner <jwerner@...omium.org>
Cc:	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Heiko Stuebner <heiko@...ech.de>,
	addy ke <addy.ke@...k-chips.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-spi@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] spi/rockchip: Add device tree property to configure
 Rx Sample Delay

Julius,

On Thu, Mar 26, 2015 at 4:30 PM, Julius Werner <jwerner@...omium.org> wrote:
> We have found that we can sometimes see read failures on boards with
> high-capacitance SPI lines. It seems that the controller samples the Rx
> data line too early, and its register interface has an "Rx Sample Delay"
> setting to fine-tune against this issue.
>
> This patch adds a new optional device tree entry that can configure this
> delay in terms of nanoseconds. The kernel will calculate the
> best-fitting amount of parent clock ticks to program the controller with
> based on that.
>
> Signed-off-by: Julius Werner <jwerner@...omium.org>
> ---
>  .../devicetree/bindings/spi/spi-rockchip.txt        |  4 ++++
>  drivers/spi/spi-rockchip.c                          | 21 +++++++++++++++++++++
>  2 files changed, 25 insertions(+)

Reviewed-by: Doug Anderson <dianders@...omium.org>
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