linux-kernel - Re: [PATCH 1/2] dt-bindings: spi: Add Spreadtrum ADI controller documentation

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Date:   Thu, 7 Sep 2017 10:54:35 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Baolin Wang <baolin.wang@...eadtrum.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-spi@...r.kernel.org,
        devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: spi: Add Spreadtrum ADI controller
 documentation

On Thu, Sep 07, 2017 at 11:29:05AM +0800, Baolin Wang wrote:
> On 6 September 2017 at 22:59, Mark Brown <broonie@...nel.org> wrote:
> > On Wed, Sep 06, 2017 at 02:10:43PM +0800, Baolin Wang wrote:

> >> +- hwlocks: Reference to a phandle of a hwlock provider node.
> >> +- hwlock-names: Reference to hwlock name strings defined in the same order
> >> +     as the hwlocks.

> > What are these hwlocks protecting, and what names are expected?

> I made one explanation in above sentence, I assume it is not clear.
> Since we have multi-subsystems will use ADI to access analog chip,
> when one system is reading/writing data by ADI, which should be under
> one hardware spinlock protection to prevent other systems from
> reading/writing data by ADI at the same time, or two parallel routine
> of setting ADI registers will get incorrect results.

> The hwspinlock name should be "adi", and I will make it clear in next version.

So there's other drivers that might also be accessing this IP block?

> >> +Optional properties:
> >> +- sprd,hw-channels: Specify the hardware channel number and mapped address
> >> +     for hardware channel accessing.

> > What do these mean and how are the numbers and how will the binding be
> > interpreted?

> I also gave one explanation in above sentence, is it not clear? I try again.

It says what they are, it doesn't say for example what a hardware
channel is or how those numbers map onto the actual hardware.

> ADI controller has 50 channels including 2 software read/write
> channels and 48 hardware channels to access analog chip. For 2
> software read/write channels, which means we should set ADI registers
> to access analog chip. But For hardware channels, we can just mapped
> one analog chip address to one hardware channel, then user can access
> analog chip by hardware channel without setting ADI registers.

> For this "sprd,hw-channels" property, the first value specifies the
> channel id, and the second value specifies the address which is mapped
> into analog chip space.

So does this driver control all the channels or are there other drivers
(or hardware components) that control some of the other channels?

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