Re: [PATCH v6 06/14] gtrace: Add RISC-V Trace encoder driver

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] gtrace: missing INHIBITSRC restore in rvtrace_encoder_start()
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commit 89ac751d2a47352255588950ac5d611d8f1d501f
Author: Mayuresh Chitale <mayuresh.chitale@oss.qualcomm.com>

gtrace: Add RISC-V Trace encoder driver

This commit adds the initial implementation of the RISC-V E-Trace encoder
driver. The encoder generates trace data for its bound CPU as defined in the
RISC-V Trace Control Interface specification.

> diff --git a/drivers/hwtracing/gtrace/rvtrace-encoder.c b/drivers/hwtracing/gtrace/rvtrace-encoder.c
> new file mode 100644
> index 0000000000000..1f06b1a2b4128
> --- /dev/null
> +++ b/drivers/hwtracing/gtrace/rvtrace-encoder.c

[ ... ]

> +static int rvtrace_encoder_start(struct gtrace_component *comp)
> +{
> +	struct rvtrace_encoder_priv *priv = dev_get_drvdata(&comp->dev);
> +	struct gtrace_platform_data *pdata = comp->pdata;
> +	int ret;
> +	u32 val;
> +
> +	if (priv->srcbits)
> +		rvtrace_encoder_set_srcid(pdata, priv->srcbits);
> +
> +	ret = rvtrace_encoder_set_format(pdata);

[Severity: Medium]
Does this skip restoring the INHIBITSRC bit when priv->srcbits is 0?

If the device loses context (for example, during power state changes when the
component is disabled and re-enabled) and tracing is started on a CPU where
source ID tracing is unsupported, could the hardware emit trace packets with
uninitialized or garbage source IDs?

During rvtrace_encoder_probe(), INHIBITSRC is explicitly set when
priv->srcbits is 0:

	if (!priv->srcbits) {
		...
		val = gtrace_read32(pdata, RVTRACE_COMPONENT_CTRL_OFFSET);
		val |= BIT(RVTRACE_COMPONENT_CTRL_INHIBITSRC_SHIFT);
		gtrace_write32(pdata, val, RVTRACE_COMPONENT_CTRL_OFFSET);
	}

Should rvtrace_encoder_start() also restore this state to ensure complete
hardware state initialization?

> +	if (ret) {
> +		dev_err(&comp->dev, "failed to set format %d\n", pdata->format);
> +		return ret;
> +	}

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Sashiko AI review · https://sashiko.dev/#/patchset/20261001052243.3042627-1-mayuresh.chitale@oss.qualcomm.com?part=6