Re: [PATCH v2 04/11] ARM: tegra: Set spi-max-frequency property to flash node
From: Stephen Warren
Date: Tue Jan 27 2015 - 11:48:48 EST
On 01/27/2015 04:13 AM, Tomeu Vizoso wrote:
On 15 January 2015 at 18:26, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote:
On 01/15/2015 09:12 AM, Tomeu Vizoso wrote:
To silence a warning on Nyan boards.
Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
---
arch/arm/boot/dts/tegra124-nyan-big.dts | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts
b/arch/arm/boot/dts/tegra124-nyan-big.dts
index 9a9cffe..94c7ba9 100644
--- a/arch/arm/boot/dts/tegra124-nyan-big.dts
+++ b/arch/arm/boot/dts/tegra124-nyan-big.dts
@@ -1660,6 +1660,7 @@
flash@0 {
compatible = "winbond,w25q32dw";
+ spi-max-frequency = <25000000>;
This property already exists in the SPI controller. Isn't the max frequency
supposed to inherit from there? If so, shouldn't the code not warn when such
inheritance happens, i.e. it'd be better to fix the code?
I don't think it's supposed to fall back to the controller's max freq,
as each device has its own maximum frequency that it can support and
it's not related to what the master supports.
If the controller-specific frequency property isn't ever used, we should
remove it. No point carrying cruft that looks like it does something but
doesn't.
Logically, each device's max frequency certainly should be influenced by
all of the controller, board, and device max frequency. Those should all
impose a cap on the speed used. I'd expect this to be expressed in DT as
a single property in each device where the user has calculated that max
for the device, with the option to have all the devices fall back to the
"default" provided at the controller/bus level if the device imposes a
cap that's no lower.
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