Re: [PATCH] coresight: tmc: Refactor loops in etb dump

From: Mathieu Poirier
Date: Mon Sep 10 2018 - 13:17:41 EST


On Wed, 5 Sep 2018 at 04:09, Leo Yan <leo.yan@xxxxxxxxxx> wrote:
>
> In ETB dump function tmc_etb_dump_hw() it has nested loops. The second
> level loop is to iterate index in the range [0 .. drvdata->memwidth);
> but the index isn't really used in the code, thus the second level
> loop is useless.
>
> This patch is to remove the second level loop; the refactor also reduces
> indentation and we can use 'break' to replace 'goto' tag.
>
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> ---
> drivers/hwtracing/coresight/coresight-tmc-etf.c | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index 9c599c9..8b34161 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -34,23 +34,20 @@ static void tmc_etb_dump_hw(struct tmc_drvdata *drvdata)
> {
> char *bufp;
> u32 read_data, lost;
> - int i;
>
> /* Check if the buffer wrapped around. */
> lost = readl_relaxed(drvdata->base + TMC_STS) & TMC_STS_FULL;
> bufp = drvdata->buf;
> drvdata->len = 0;
> while (1) {
> - for (i = 0; i < drvdata->memwidth; i++) {
> - read_data = readl_relaxed(drvdata->base + TMC_RRD);
> - if (read_data == 0xFFFFFFFF)
> - goto done;
> - memcpy(bufp, &read_data, 4);
> - bufp += 4;
> - drvdata->len += 4;
> - }
> + read_data = readl_relaxed(drvdata->base + TMC_RRD);
> + if (read_data == 0xFFFFFFFF)
> + break;
> + memcpy(bufp, &read_data, 4);
> + bufp += 4;
> + drvdata->len += 4;

I implemented these loops in accordance with the reference manual,
which is advising to read one ETB memory word at a time. But taking a
step back getting rid of the inner loop yields exactly the same
result. So I'll go ahead and apply your patch.

Thanks,
Mathieu

> }
> -done:
> +
> if (lost)
> coresight_insert_barrier_packet(drvdata->buf);
> return;
> --
> 2.7.4
>