linux-kernel - Re: [PATCH] usb: dwc3: qcom: Remove useless compatible strings from the match table

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Date:   Thu, 12 Dec 2019 15:23:49 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Manu Gautam <mgautam@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Sandeep Maheswaram <sanm@...eaurora.org>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: dwc3: qcom: Remove useless compatible strings from
 the match table

On Thu 12 Dec 13:21 PST 2019, Douglas Anderson wrote:

> The of match table in dwc3-qcom.c had an entry per Qualcomm SoC known
> to have dwc3.  That's not needed.  Here's why:
> 
> 1. The bindings specify that the compatible string in the device tree
>    should contain the SoC-specific compatible string followed by the
>    string "qcom,dwc3".
> 
> 2. All known Qualcomm SoC dts files (confirmed via git grep in
>    mainline Linux) using dwc3 follow the rules and do, in fact,
>    contain the SoC-specific compatible string followed by the string
>    "qcom,dwc3".
> 
> 3. The source code does nothing special with the per-SoC strings--they
>    are only used to match the node.
> 
> Let's remove the extra strings from the table.  Doing so will avoid
> the need to land future useless patches [1] that do nothing more than
> add yet more strings to the table.
> 
> NOTE: if later we _do_ find some SoC-specific quirk we need to handle
> in the code we can add back a subset of these strings.  At the time we
> will probably also add some data in the match table to make it easier
> to generalize this hypothetical quirk across all the SoCs it affects.
> 
> [1] https://lore.kernel.org/r/1574940787-1004-2-git-send-email-sanm@codeaurora.org
> 

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
>  drivers/usb/dwc3/dwc3-qcom.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index 261af9e38ddd..72e867e02a1c 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -751,9 +751,6 @@ static const struct dev_pm_ops dwc3_qcom_dev_pm_ops = {
>  
>  static const struct of_device_id dwc3_qcom_of_match[] = {
>  	{ .compatible = "qcom,dwc3" },
> -	{ .compatible = "qcom,msm8996-dwc3" },
> -	{ .compatible = "qcom,msm8998-dwc3" },
> -	{ .compatible = "qcom,sdm845-dwc3" },
>  	{ }
>  };
>  MODULE_DEVICE_TABLE(of, dwc3_qcom_of_match);
> -- 
> 2.24.1.735.g03f4e72817-goog
>