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[188.141.3.169]) by smtp.gmail.com with ESMTPSA id d14-20020adffbce000000b002bddd75a83fsm3061349wrs.8.2023.01.13.17.40.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Jan 2023 17:40:20 -0800 (PST) Message-ID: <5e1f37ba-494a-19d2-e412-7631508ab142@linaro.org> Date: Sat, 14 Jan 2023 01:40:19 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH] interconnect: Skip call into provider if initial bw is zero Content-Language: en-US From: Bryan O'Donoghue To: Vivek Aknurwar , djakov@kernel.org Cc: quic_mdtipton@quicinc.com, quic_okukatla@quicinc.com, linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org References: <1673647679-15216-1-git-send-email-quic_viveka@quicinc.com> <83a7bfed-3b16-3d01-b1b2-f197252bd0b1@linaro.org> In-Reply-To: <83a7bfed-3b16-3d01-b1b2-f197252bd0b1@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 14/01/2023 01:24, Bryan O'Donoghue wrote: > On 13/01/2023 22:07, Vivek Aknurwar wrote: >> Currently framework sets bw even when init bw requirements are zero >> during >> provider registration, thus resulting bulk of set bw to hw. >> Avoid this behaviour by skipping provider set bw calls if init bw is >> zero. >> >> Signed-off-by: Vivek Aknurwar >> --- >>   drivers/interconnect/core.c | 17 ++++++++++------- >>   1 file changed, 10 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c >> index 25debde..43ed595 100644 >> --- a/drivers/interconnect/core.c >> +++ b/drivers/interconnect/core.c >> @@ -977,14 +977,17 @@ 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 (provider->pre_aggregate) >> -        provider->pre_aggregate(node); >> - >> -    if (provider->aggregate) >> -        provider->aggregate(node, 0, node->init_avg, node->init_peak, >> -                    &node->avg_bw, &node->peak_bw); >> +    if (node->avg_bw || node->peak_bw) { >> +        if (provider->pre_aggregate) >> +            provider->pre_aggregate(node); >> + >> +        if (provider->aggregate) >> +            provider->aggregate(node, 0, node->init_avg, >> node->init_peak, >> +                        &node->avg_bw, &node->peak_bw); >> +        if (provider->set) >> +            provider->set(node, node); >> +    } >> -    provider->set(node, node); >>       node->avg_bw = 0; >>       node->peak_bw = 0; > > I have the same comment/question for this patch that I had for the qcom > arch specific version of it. This patch seems to be doing at a higher > level what the patch below was doing at a lower level. > > https://lore.kernel.org/lkml/1039a507-c4cd-e92f-dc29-1e2169ce5078@linaro.org/T/#m0c90588d0d1e2ab88c39be8f5f3a8f0b61396349 > > what happens to earlier silicon - qcom silicon which previously made > explicit zero requests ? > > https://lore.kernel.org/lkml/1039a507-c4cd-e92f-dc29-1e2169ce5078@linaro.org/T/#m589e8280de470e038249bb362634221771d845dd > > https://lkml.org/lkml/2023/1/3/1232 > > Isn't it a better idea to let lower layer drivers differentiate what > they do ? > > For example on pre 5.4 qcom kernel silicon we might choose to set the > value to zero "because that's what the reference code did" but on newer > silicon we might opt to skip the zero configuration ? > > I'm happy to be shown the error of my ways but, absent testing to *show* > it doesn't impact existing legacy silicon, I think we should be wary of > this change. > > --- > bod Oh, and what is the effect on Samsung and i.MX silicon interconnect providers of skipping the zero set ? --- bod