linux-kernel - Re: [PATCH v10 4/7] qcom-tgu: Add TGU decode support

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Message-ID: <beb63598-a7fc-4e77-a68e-8622fbd93972@oss.qualcomm.com>
Date: Tue, 13 Jan 2026 12:13:05 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Songwei Chai <songwei.chai@....qualcomm.com>, andersson@...nel.org,
        alexander.shishkin@...ux.intel.com, mike.leach@...aro.org,
        suzuki.poulose@....com, james.clark@....com, krzk+dt@...nel.org,
        conor+dt@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, coresight@...ts.linaro.org,
        devicetree@...r.kernel.org, gregkh@...uxfoundation.org
Subject: Re: [PATCH v10 4/7] qcom-tgu: Add TGU decode support

On 1/9/26 3:11 AM, Songwei Chai wrote:
> Decoding is when all the potential pieces for creating a trigger
> are brought together for a given step. Example - there may be a
> counter keeping track of some occurrences and a priority-group that
> is being used to detect a pattern on the sense inputs. These 2
> inputs to condition_decode must be programmed, for a given step,
> to establish the condition for the trigger, or movement to another
> steps.
> 
> Signed-off-by: Songwei Chai <songwei.chai@....qualcomm.com>
> ---

[...]

> @@ -18,8 +18,36 @@ static int calculate_array_location(struct tgu_drvdata *drvdata,
>  				   int step_index, int operation_index,
>  				   int reg_index)
>  {
> -	return operation_index * (drvdata->max_step) * (drvdata->max_reg) +
> -		step_index * (drvdata->max_reg) + reg_index;

I think this type of calculations could use a wrapper

> +	int ret = -EINVAL;
> +
> +	switch (operation_index) {
> +	case TGU_PRIORITY0:
> +	case TGU_PRIORITY1:
> +	case TGU_PRIORITY2:
> +	case TGU_PRIORITY3:
> +		ret = operation_index * (drvdata->max_step) *
> +			(drvdata->max_reg) +
> +			step_index * (drvdata->max_reg) + reg_index;
> +		break;
> +	case TGU_CONDITION_DECODE:
> +		ret = step_index * (drvdata->max_condition_decode) +
> +			reg_index;
> +		break;
> +	default:
> +		break;
> +	}
> +	return ret;

The only thing your switch statement is assign a value to ret and break
out. Change that to a direct return, and drop 'ret' altogether


> +}
> +
> +static int check_array_location(struct tgu_drvdata *drvdata, int step,
> +				int ops, int reg)
> +{
> +	int result = calculate_array_location(drvdata, step, ops, reg);
> +
> +	if (result == -EINVAL)
> +		dev_err(drvdata->dev, "%s - Fail\n", __func__);

Avoid __func__.

The error message is very non-descriptive

[...]

>  static int tgu_enable(struct device *dev)
>  {
>  	struct tgu_drvdata *drvdata = dev_get_drvdata(dev);
> +	int ret = 0;
>  
>  	guard(spinlock)(&drvdata->lock);
>  	if (drvdata->enable)
>  		return -EBUSY;
>  
> -	tgu_write_all_hw_regs(drvdata);
> +	ret = tgu_write_all_hw_regs(drvdata);
> +
> +	if (ret == -EINVAL)

stray \n
> +		goto exit;
> +
>  	drvdata->enable = true;
>  
> -	return 0;
> +exit:
> +	return ret;

ret = tgu_write_all_hw_regs(drvdata);
if (!ret)
	drvdata->enable = true;

return ret

Konrad