Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> writes:
> Adding an ETB10 specific AUX area operations to be used
> by the perf framework when events are initialised.
>
> Part of this operation involves modeling the mmap'ed area
> based on the specific ways a sink buffer gathers information.
I don't mind being CC'd on the rest of the patches too, btw. :)
> +static unsigned long etb_reset_buffer(struct coresight_device *csdev,
> + struct perf_output_handle *handle,
> + void *sink_config, bool *lost)
> +{
> + unsigned long size = 0;
> + struct cs_buffers *buf = sink_config;
> +
> + if (buf) {
> + /*
> + * In snapshot mode ->data_size holds the new address of the
> + * ring buffer's head. The size itself is the whole address
> + * range since we want the latest information.
> + */
> + if (buf->snapshot)
> + handle->head = local_xchg(&buf->data_size,
> + buf->nr_pages << PAGE_SHIFT);
> +
> + /*
> + * Tell the tracer PMU how much we got in this run and if
> + * something went wrong along the way. Nobody else can use
> + * this cs_buffers instance until we are done. As such
> + * resetting parameters here and squaring off with the ring
> + * buffer API in the tracer PMU is fine.
> + */
> + *lost = local_xchg(&buf->lost, 0);
This is a thin ice, you can't really make assumptions about bool's
storage size or even type, afaict.
> + size = local_xchg(&buf->data_size, 0);
> + }
> +
> + return size;
> +}
> +
> +static void etb_update_buffer(struct coresight_device *csdev,
> + struct perf_output_handle *handle,
> + void *sink_config)
> +{
> + int i, cur;
> + u8 *buf_ptr;
> + u32 read_ptr, write_ptr, capacity;
> + u32 status, read_data, to_read;
> + unsigned long flags, offset;
> + struct cs_buffers *buf = sink_config;
> + struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> + if (!buf)
> + return;
> +
> + capacity = drvdata->buffer_depth * ETB_FRAME_SIZE_WORDS;
> +
> + spin_lock_irqsave(&drvdata->spinlock, flags);
This spinlock seems to be held over the entire readout operation,
however, I can't find clear rules wrt what structures etc are serialized
on it. Instead, the comment says "only one at a time pls". Same for
etm's big drvdata spinlock.
Regards,
--
Alex
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