linux-kernel - Re: [PATCH v6 09/13] Add nodes for dsb edge control

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Message-ID: <2023062848-shimmer-variety-c08e@gregkh>
Date:   Wed, 28 Jun 2023 08:13:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Tao Zhang <quic_taozha@...cinc.com>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jinlong Mao <quic_jinlmao@...cinc.com>,
        Leo Yan <leo.yan@...aro.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Hao Zhang <quic_hazha@...cinc.com>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org
Subject: Re: [PATCH v6 09/13] Add nodes for dsb edge control

On Wed, Jun 28, 2023 at 11:11:29AM +0800, Tao Zhang wrote:
> 
> On 6/20/2023 4:49 PM, Greg Kroah-Hartman wrote:
> > On Tue, Jun 20, 2023 at 04:31:59PM +0800, Tao Zhang wrote:
> > > On 6/20/2023 3:37 PM, Greg Kroah-Hartman wrote:
> > > > On Tue, Jun 20, 2023 at 03:32:37PM +0800, Tao Zhang wrote:
> > > > > Add the nodes to set value for DSB edge control and DSB edge
> > > > > control mask. Each DSB subunit TPDM has maximum of n(n<16) EDCR
> > > > > resgisters to configure edge control. DSB edge detection control
> > > > > 00: Rising edge detection
> > > > > 01: Falling edge detection
> > > > > 10: Rising and falling edge detection (toggle detection)
> > > > > And each DSB subunit TPDM has maximum of m(m<8) ECDMR registers to
> > > > > configure mask. Eight 32 bit registers providing DSB interface
> > > > > edge detection mask control.
> > > > > 
> > > > > Signed-off-by: Tao Zhang<quic_taozha@...cinc.com>
> > > > > ---
> > > > >    .../ABI/testing/sysfs-bus-coresight-devices-tpdm   |  32 +++++
> > > > >    drivers/hwtracing/coresight/coresight-tpdm.c       | 143 ++++++++++++++++++++-
> > > > >    drivers/hwtracing/coresight/coresight-tpdm.h       |  22 ++++
> > > > >    3 files changed, 196 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
> > > > > index 2a82cd0..34189e4a 100644
> > > > > --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
> > > > > +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
> > > > > @@ -60,3 +60,35 @@ Description:
> > > > >    		Bit[3] : Set to 0 for low performance mode.
> > > > >    				 Set to 1 for high performance mode.
> > > > >    		Bit[4:8] : Select byte lane for high performance mode.
> > > > > +
> > > > > +What:		/sys/bus/coresight/devices/<tpdm-name>/dsb_edge_ctrl
> > > > > +Date:		March 2023
> > > > > +KernelVersion	6.5
> > > > > +Contact:	Jinlong Mao (QUIC)<quic_jinlmao@...cinc.com>, Tao Zhang (QUIC)<quic_taozha@...cinc.com>
> > > > > +Description:
> > > > > +		Read/Write a set of the edge control registers of the DSB
> > > > > +		in TPDM.
> > > > > +
> > > > > +		Expected format is the following:
> > > > > +		<integer1> <integer2> <integer3>
> > > > sysfs is "one value", not 3.  Please never have to parse a sysfs file.
> > > Do you mean sysfs file can only accept "one value"?
> > Yes.
> 
> Hi Greg,
> 
> 
> I‘d like to clarify the usage of this sysfs file again.
> 
> In the current design, three integers will be written to "dsb_edge_ctrl" to
> configure DSB edge detection.
> 
> Integer #1: The start number of edge detection which needs to be configured.
> 
> Integer #2: The end number of edge detection which needs to be configured.
> 
> Integer #3: The type of the edge detection needs to be configured.

All of this is wrong.  Again, sysfs is "one value per file"

> Below is an example.
> 
> echo 0x3 0x25 0x1 > dsb_edge_ctrl
> 
> It will configure edge detection #3 to #37 as "falling edge detection".
> 
> Since these three integers are interrelated and written to achieve the same
> function, can we use these three integers as "one tuple" here?

Nope!

sorry,

greg k-h