linux-kernel - Re: [PATCH V8 2/7] interconnect: core: Add dynamic id allocation support

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Message-ID: <6j576swreyqcyu7ryxtyojjmo7clfwb7fibw2aeuvif5vzexpq@du2farsldpti>
Date: Mon, 17 Feb 2025 03:02:28 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>
Cc: Georgi Djakov <djakov@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Odelu Kukatla <quic_okukatla@...cinc.com>, Mike Tipton <quic_mdtipton@...cinc.com>, 
	Jeff Johnson <quic_jjohnson@...cinc.com>, Andrew Halaney <ahalaney@...hat.com>, 
	Sibi Sankar <quic_sibis@...cinc.com>, linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 2/7] interconnect: core: Add dynamic id allocation
 support

On Sun, Feb 16, 2025 at 10:08:51PM +0530, Raviteja Laggyshetty wrote:
> 
> 
> On 2/10/2025 4:20 PM, Dmitry Baryshkov wrote:
> > On Wed, Feb 05, 2025 at 06:27:38PM +0000, Raviteja Laggyshetty wrote:
> >> The current interconnect framework relies on static IDs for node
> >> creation and registration, which limits topologies with multiple
> >> instances of the same interconnect provider. To address this, update
> >> the interconnect framework APIs icc_node_create() and icc_link_create()
> >> APIs to dynamically allocate IDs for interconnect nodes during creation.
> >> This change removes the dependency on static IDs, allowing multiple
> >> instances of the same hardware, such as EPSS L3.
> >>
> >> Signed-off-by: Raviteja Laggyshetty <quic_rlaggysh@...cinc.com>
> >> ---
> >>  drivers/interconnect/core.c | 13 ++++++++++++-
> >>  1 file changed, 12 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
> >> index 9d5404a07e8a..40700246f1b6 100644
> >> --- a/drivers/interconnect/core.c
> >> +++ b/drivers/interconnect/core.c
> >> @@ -20,6 +20,8 @@
> >>  
> >>  #include "internal.h"
> >>  
> >> +#define ICC_DYN_ID_START 10000
> >> +
> >>  #define CREATE_TRACE_POINTS
> >>  #include "trace.h"
> >>  
> >> @@ -826,7 +828,12 @@ static struct icc_node *icc_node_create_nolock(int id)
> >>  	if (!node)
> >>  		return ERR_PTR(-ENOMEM);
> >>  
> >> -	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
> >> +	/* negative id indicates dynamic id allocation */
> >> +	if (id < 0)
> > 
> > Nit: I think it might be better to add an explicit define for that and
> > to decline all other negatdive values. Please leave us some room for
> > future expansion.
> > 
> Do you mean to replace the value of ALLOC_DYN_ID from -1 to some
> positive value like 100000 and to use it as initial ID for the nodes
> requiring the dynamic allocation ? This explicit define can be used as
> check for dynamic allocation and also as argument to idr_alloc min value
> argument. Is my interpretation of the comment correct ?

No, it is not. I asked to add an explicit define for -1 in the ICC
framework and make icc_node_create_nolock() reject all other negative
values.

> 
> >> +		id = idr_alloc(&icc_idr, node, ICC_DYN_ID_START, 0, GFP_KERNEL);
> >> +	else
> >> +		id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
> >> +
> >>  	if (id < 0) {
> >>  		WARN(1, "%s: couldn't get idr\n", __func__);
> >>  		kfree(node);
> >> @@ -962,6 +969,10 @@ void icc_node_add(struct icc_node *node, struct icc_provider *provider)
> >>  	node->avg_bw = node->init_avg;
> >>  	node->peak_bw = node->init_peak;
> >>  
> >> +	if (node->id >= ICC_DYN_ID_START)
> >> +		node->name = devm_kasprintf(provider->dev, GFP_KERNEL, "%s@%s",
> >> +					    node->name, dev_name(provider->dev));
> >> +
> >>  	if (node->avg_bw || node->peak_bw) {
> >>  		if (provider->pre_aggregate)
> >>  			provider->pre_aggregate(node);
> >> -- 
> >> 2.39.2
> >>
> > 
> 

-- 
With best wishes
Dmitry