[PATCH] ARM64: dts: marvell: armada-cp110: Add registers clock for SPI nodes

From: gregory.clement@free-electrons.com (Gregory CLEMENT)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM64: dts: marvell: armada-cp110: Add registers clock for SPI nodes
Date: Tue, 30 Jan 2018 14:03:24 +0100	[thread overview]
Message-ID: <87372n1otf.fsf@free-electrons.com> (raw)
In-Reply-To: <20180130135320.39899ef5@windsurf.lan> (Thomas Petazzoni's message of "Tue, 30 Jan 2018 13:53:20 +0100")

Hi Thomas,

 On mar., janv. 30 2018, Thomas Petazzoni <thomas.petazzoni@free-electrons.com> wrote:

> Hello,
>
> On Tue, 30 Jan 2018 13:42:41 +0100, Gregory CLEMENT wrote:
>
>> > On Tue, Jan 30, 2018 at 01:21:38PM +0200, Baruch Siach wrote:  
>> >> On Tue, Jan 30, 2018 at 12:14:55PM +0100, Gregory CLEMENT wrote:  
>> >> > This extra clock is needed to access the registers of the SPI controller
>> >> > used on Armada 7K/8K SoCs.  
>> >> 
>> >> Don't we need this also for I2C and UART?  
>> >
>> > So you posted a patch for I2C as well.
>> >
>> > Looking at the cp110-system-controller.c driver (cp110_syscon_common_probe()), 
>> > I see that clock gate #17 (CP110_GATE_MAIN) is automatically enabled when #21 
>> > (CP110_GATE_SLOW_IO) is enabled. So this additional clock specifier should not 
>> > be needed.  
>> 
>> Actually this is the reason of these changes. The clock driver is wrong,
>> now that we got new documentation about the clocks, we saw that the
>> clock tree descried in this driver was not correct. There is no relation
>> between clock 17 and clock 21 for instance. But in order to be able to
>> fix the clock driver, first we have to make sure that all the driver of
>> the peripherals really select their own clocks.
>> 
>> I have already the patch fixing the clock ready and once I will have
>> converted the remaining peripheral I will be able to submit it.
>
> Of course I do agree with Gr?gory here, since we discussed this at
> length. However, I think Baruch has a point in that this should be
> explained in the commit log.

It was explained in the series modifying the drivers. But here it is
only about correctly describing the hardware ressource in the device
tree, the fact that the linux clock driver may or not automatically
select some of the clock should not be taking into account.

Gregory

>
> Thomas
> -- 
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com
>
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-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com