linux-kernel - Re: [PATCH 2/2] ARM: dts: dra7x: Support QSPI MODE-0 operation at 64MHz

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Message-ID: <20160414171215.GA9860@rob-hp-laptop>
Date:	Thu, 14 Apr 2016 12:12:15 -0500
From:	Rob Herring <robh@...nel.org>
To:	Vignesh R <vigneshr@...com>
Cc:	Tony Lindgren <tony@...mide.com>, nsekhar@...com,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] ARM: dts: dra7x: Support QSPI MODE-0 operation at
 64MHz

On Thu, Apr 14, 2016 at 03:48:21PM +0530, Vignesh R wrote:
> According to Data Manual(SPRS915P) of AM57x, TI QSPI controller on
> DRA74(rev 1.1+)/DRA72 EVM can support up to 64MHz in MODE-0, whereas
> MODE-3 is limited to 48MHz. Hence, switch to MODE-0 for better
> throughput.
> 
> Signed-off-by: Vignesh R <vigneshr@...com>
> ---
>  Documentation/devicetree/bindings/spi/ti_qspi.txt | 7 +++++++
>  arch/arm/boot/dts/dra7-evm.dts                    | 6 ++----
>  arch/arm/boot/dts/dra72-evm.dts                   | 6 ++----
>  3 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/ti_qspi.txt b/Documentation/devicetree/bindings/spi/ti_qspi.txt
> index cc8304aa64ac..50b14f6b53a3 100644
> --- a/Documentation/devicetree/bindings/spi/ti_qspi.txt
> +++ b/Documentation/devicetree/bindings/spi/ti_qspi.txt
> @@ -19,6 +19,13 @@ Optional properties:
>  - syscon-chipselects: Handle to system control region contains QSPI
>  		      chipselect register and offset of that register.
>  
> +NOTE: TI QSPI controller requires different pinmux and IODelay
> +paramaters for Mode-0 and Mode-3 operations, which needs to be set up by
> +the bootloader (U-Boot). Default configuration only supports Mode-0
> +operation. Hence, "spi-cpol" and "spi-cpha" DT properties cannot be
> +specified in the slave nodes of TI QSPI controller without appropriate
> +modification to bootloader.

But these properties are properties of what the slave device supports, 
right? I don't see how you can change them based on the controller.

Rob