Hi Leo,
On 10/07/2021 08:02, Leo Yan wrote:
Current code syncs the buffer range is [offset, offset+len), it doesn't consider the case when the trace data is wrapped around, in this case 'offset+len' is bigger than 'etr_buf->size'. Thus it syncs buffer out of the memory buffer, and it also misses to sync buffer from the start of the memory.
I doubt this claim is valid. We do the sync properly, taking the page corresponding to the "offset" wrapping it around in "page" index.
Here is the code :
void tmc_sg_table_sync_data_range(struct tmc_sg_table *table, u64 offset, u64 size) { int i, index, start; int npages = DIV_ROUND_UP(size, PAGE_SIZE); struct device *real_dev = table->dev->parent; struct tmc_pages *data = &table->data_pages;
start = offset >> PAGE_SHIFT; for (i = start; i < (start + npages); i++) { index = i % data->nr_pages; dma_sync_single_for_cpu(real_dev, data->daddrs[index], PAGE_SIZE, DMA_FROM_DEVICE); } }
See that the npages accounts for the "size" requested and we wrap the "index" by the total number of pages in the buffer and pick the right page.
So, I think this fix is not needed.
Cheers Suzuki
This patch corrects the memory sync ranges, when detects the wrapping around case, it splits into two chunks: one chunk is the tail of the buffer and another chunk is from the start of the buffer after wrapping around.
Signed-off-by: Leo Yan leo.yan@linaro.org
.../hwtracing/coresight/coresight-tmc-etr.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index 888b0f929d33..a1afefcbf175 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -780,7 +780,23 @@ static void tmc_etr_sync_sg_buf(struct etr_buf *etr_buf, u64 rrp, u64 rwp) else etr_buf->len = ((w_offset < r_offset) ? etr_buf->size : 0) + w_offset - r_offset;
- tmc_sg_table_sync_data_range(table, r_offset, etr_buf->len);
- if (r_offset + etr_buf->len > etr_buf->size) {
int len1, len2;/** If trace data is wrapped around, sync AUX bounce buffer* for two chunks: "len1" is for the trace date length at* the tail of bounce buffer, and "len2" is the length from* the start of the buffer after wrapping around.*/len1 = etr_buf->size - r_offset;len2 = etr_buf->len - len1;tmc_sg_table_sync_data_range(table, r_offset, len1);tmc_sg_table_sync_data_range(table, 0, len2);- } else {
tmc_sg_table_sync_data_range(table, r_offset, etr_buf->len);- } }
static const struct etr_buf_operations etr_sg_buf_ops = {