From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 04/11] ARM: tegra: Set spi-max-frequency property to flash node
Date: Tue, 27 Jan 2015 09:48:43 -0700 [thread overview]
Message-ID: <54C7C16B.2080003@wwwdotorg.org> (raw)
In-Reply-To: <CAAObsKDx_W23OTL2RE4xxgXL-rtp3npkBtx6qMHV1j8ZXmo1rw@mail.gmail.com>
On 01/27/2015 04:13 AM, Tomeu Vizoso wrote:
> On 15 January 2015 at 18:26, Stephen Warren <swarren@wwwdotorg•org> 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@collabora•com>
>>> ---
>>> 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 at 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.
next prev parent reply other threads:[~2015-01-27 16:48 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1421338359-27467-1-git-send-email-tomeu.vizoso@collabora.com>
2015-01-15 16:12 ` [PATCH v2 01/11] ARM: tegra: Add node for trackpad in Nyan boards Tomeu Vizoso
2015-01-15 16:12 ` [PATCH v2 02/11] ARM: tegra: Use the generated pinmux data Tomeu Vizoso
2015-01-15 17:25 ` Stephen Warren
2015-01-20 13:59 ` Tomeu Vizoso
2015-01-20 16:20 ` Stephen Warren
2015-01-15 16:12 ` [PATCH v2 03/11] ARM: tegra: Set the sound card model that alsaucm expects Tomeu Vizoso
2015-01-15 17:22 ` Stephen Warren
2015-01-16 8:50 ` Tomeu Vizoso
2015-01-16 9:01 ` Tomeu Vizoso
2015-01-19 17:10 ` Stephen Warren
2015-01-19 17:11 ` Tomeu Vizoso
2015-01-20 17:01 ` Dylan Reid
2015-01-15 16:12 ` [PATCH v2 04/11] ARM: tegra: Set spi-max-frequency property to flash node Tomeu Vizoso
2015-01-15 17:26 ` Stephen Warren
2015-01-27 11:13 ` Tomeu Vizoso
2015-01-27 16:48 ` Stephen Warren [this message]
2015-01-28 10:24 ` Tomeu Vizoso
2015-01-15 16:12 ` [PATCH v2 06/11] ARM: tegra: Move out nyan-generic parts out from the nyan-big DT Tomeu Vizoso
2015-01-15 17:28 ` Stephen Warren
2015-01-27 12:57 ` Tomeu Vizoso
2015-01-15 16:12 ` [PATCH v2 07/11] ARM: tegra: Add DTS for the nyan-blaze board Tomeu Vizoso
2015-01-15 16:12 ` [PATCH v2 09/11] ARM: tegra: Use pwrseq-simple for the wifi in Nyan Tomeu Vizoso
2015-01-15 17:34 ` Stephen Warren
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