Hello Elen Song,
The patch d48de6f1a81b: "DMA: AT91: Get residual bytes in dma buffer"
from May 10, 2013, leads to the following static checker warning:
drivers/dma/at_hdmac.c:299 atc_get_bytes_left()
warn: unsigned 'atchan->remain_desc' is never less than zero.
drivers/dma/at_hdmac.c
289 if (unlikely(test_bit(ATC_IS_BTC, &atchan->status))) {
290 clear_bit(ATC_IS_BTC, &atchan->status);
291 desc_cur = atc_get_current_descriptors(atchan,
292 channel_readl(atchan, DSCR));
293 if (!desc_cur) {
294 ret = -EINVAL;
295 goto out;
296 }
297 atchan->remain_desc -= (desc_cur->lli.ctrla & ATC_BTSIZE_MAX)
298 << (desc_first->tx_width);
299 if (atchan->remain_desc < 0) {
300 ret = -EINVAL;
301 goto out;
We never hit this "goto out" because atchan->remain_desc is a u32.
302 } else {
303 ret = atchan->remain_desc;
304 }
305 } else {
306 /*
307 * Get residual bytes when current
308 * descriptor transfer in progress.
309 */
310 count = (channel_readl(atchan, CTRLA) & ATC_BTSIZE_MAX)
311 << (desc_first->tx_width);
312 ret = atchan->remain_desc - count;
313 }
314 /*
315 * Check fifo empty.
316 */
317 if (!(dma_readl(atdma, CHSR) & AT_DMA_EMPT(chan_id)))
318 atc_issue_pending(chan);
319
320 out:
321 return ret;
322 }
regards,
dan carpenter
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