Re: [PATCH v2 04/11] ARM: tegra: Set spi-max-frequency property to flash node

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




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.

--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]
  Powered by Linux