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[209.85.219.178]) by smtp.gmail.com with ESMTPSA id o125sm1659769qkf.87.2021.03.31.08.55.57 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 31 Mar 2021 08:55:58 -0700 (PDT) Received: by mail-yb1-f178.google.com with SMTP id a143so21677183ybg.7 for ; Wed, 31 Mar 2021 08:55:57 -0700 (PDT) X-Received: by 2002:a5b:54a:: with SMTP id r10mr5658516ybp.476.1617206157416; Wed, 31 Mar 2021 08:55:57 -0700 (PDT) MIME-Version: 1.0 References: <1617190020-7931-1-git-send-email-kalyan_t@codeaurora.org> In-Reply-To: <1617190020-7931-1-git-send-email-kalyan_t@codeaurora.org> From: Doug Anderson Date: Wed, 31 Mar 2021 08:55:46 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [v1] drm/msm/disp/dpu1: fix warn stack reported during dpu resume To: Kalyan Thota Cc: y@qualcomm.com, dri-devel , linux-arm-msm , freedreno , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , LKML , Rob Clark , mkrishn@codeaurora.org, Daniel Hung-yu Wu , Matthias Kaehlcke , Michelle Dean , Steev Klimaszewski Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Wed, Mar 31, 2021 at 4:27 AM Kalyan Thota wrote: > > @@ -294,6 +294,9 @@ static int dpu_kms_parse_data_bus_icc_path(struct dpu_kms *dpu_kms) > struct icc_path *path1; > struct drm_device *dev = dpu_kms->dev; > > + if (!dpu_supports_bw_scaling(dev)) > + return 0; > + > path0 = of_icc_get(dev->dev, "mdp0-mem"); > path1 = of_icc_get(dev->dev, "mdp1-mem"); > Instead of hard coding a check for specific SoC compatible strings, why not just check to see if path0 and/or path1 are ERR_PTR(-ENODEV)? Then change dpu_supports_bw_scaling() to just return: !IS_ERR(dpu_kms->path[0]) It also seems like it would be nice if you did something if you got an error other than -ENODEV. Right now this function returns it but the caller ignores it? At least spit an error message out? > @@ -154,6 +154,15 @@ struct vsync_info { > > #define to_dpu_global_state(x) container_of(x, struct dpu_global_state, base) > > +/** > + * dpu_supports_bw_scaling: returns true for drivers that support bw scaling. > + * @dev: Pointer to drm_device structure > + */ > +static inline int dpu_supports_bw_scaling(struct drm_device *dev) > +{ > + return of_device_is_compatible(dev->dev->of_node, "qcom,sc7180-mdss"); See above, but I think this would be better as: return !IS_ERR(dpu_kms->path[0]); Specifically, I don't think of_device_is_compatible() is really designed as something to call a lot. It's doing a whole bunch of data structure parsing / string comparisons. It's OK-ish during probe (though better to use the of_match_table), but you don't want to call it on every runtime suspend / runtime resume.