2018-09-05 10:10:43

by Leo Yan

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

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 <[email protected]>
Signed-off-by: Leo Yan <[email protected]>
---
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;
}
-done:
+
if (lost)
coresight_insert_barrier_packet(drvdata->buf);
return;
--
2.7.4

2018-09-10 17:18:35

by Mathieu Poirier

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

On Wed, 5 Sep 2018 at 04:09, Leo Yan <[email protected]> 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 <[email protected]>
> Signed-off-by: Leo Yan <[email protected]>
> ---
> 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
>