linux-kernel - Re: [PATCH v2 00/15] UFS: Add OPP and interconnect support

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Date:   Fri, 21 Jul 2023 17:24:53 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     vireshk@...nel.org, nm@...com, sboyd@...nel.org,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        cw00.choi@...sung.com, andersson@...nel.org,
        konrad.dybcio@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        alim.akhtar@...sung.com, avri.altman@....com, bvanassche@....org,
        linux-scsi@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        quic_asutoshd@...cinc.com, quic_cang@...cinc.com,
        quic_nitirawa@...cinc.com, quic_narepall@...cinc.com,
        quic_bhaskarv@...cinc.com, quic_richardp@...cinc.com,
        quic_nguyenb@...cinc.com, quic_ziqichen@...cinc.com,
        bmasney@...hat.com, krzysztof.kozlowski@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 00/15] UFS: Add OPP and interconnect support

On Fri, Jul 21, 2023 at 03:12:06PM +0530, Viresh Kumar wrote:
> On 20-07-23, 11:10, Manivannan Sadhasivam wrote:
> > Hi,
> > 
> > This series adds OPP (Operating Points) support to UFSHCD driver and
> > interconnect support to Qcom UFS driver.
> > 
> > Motivation behind adding OPP support is to scale both clocks as well as
> > regulators/performance state dynamically. Currently, UFSHCD just scales
> > clock frequency during runtime with the help of "freq-table-hz" property
> > defined in devicetree. With the addition of OPP tables in devicetree (as
> > done for Qcom SDM845 and SM8250 SoCs in this series) UFSHCD can now scale
> > both clocks and performance state of power domain which helps in power
> > saving.
> > 
> > For the addition of OPP support to UFSHCD, there are changes required to
> > the OPP framework and devfreq drivers which are also added in this series.
> > 
> > Finally, interconnect support is added to Qcom UFS driver for scaling the
> > interconnect path dynamically. This is required to avoid boot crash in
> > recent SoCs and also to save power during runtime. More information is
> > available in patch 13/13.
> 
> Hi Mani,
> 
> I have picked the OPP related patches from here (apart from DT one)
> and sent them separately in a series, along with few changes from me.
> Also pushed them in my linux-next branch.
> 

Thanks Viresh! For patch 8/15, Kbuild bot has identified one potential null ptr
dereference issue. Could you please fix that in your branch?

You just need to remove the opp dereference in dev_pm_opp_get_freq_indexed()
before the IS_ERR_OR_NULL() check as below:

```
diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 66dc0d0cfaed..683e6e61f80b 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -208,9 +208,7 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_get_freq);
  */
 unsigned long dev_pm_opp_get_freq_indexed(struct dev_pm_opp *opp, u32 index)
 {
-       struct opp_table *opp_table = opp->opp_table;
-
-       if (IS_ERR_OR_NULL(opp) || index >= opp_table->clk_count) {
+       if (IS_ERR_OR_NULL(opp) || index >= opp->opp_table->clk_count) {
                pr_err("%s: Invalid parameters\n", __func__);
                return 0;
        }
```

- Mani

> Thanks.
> 
> -- 
> viresh

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