Found using smatch:
drivers/dma/at_hdmac.c:299 atc_get_bytes_left() warn: unsigned
'atchan->remain_desc' is never less than zero.

Signed-off-by: Alexandre Belloni <alexandre.bell...@free-electrons.com>
---
 drivers/dma/at_hdmac.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index c13a3bb0f594..9ec84ee2fa25 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -294,14 +294,16 @@ static int atc_get_bytes_left(struct dma_chan *chan)
                        ret = -EINVAL;
                        goto out;
                }
-               atchan->remain_desc -= (desc_cur->lli.ctrla & ATC_BTSIZE_MAX)
-                                               << (desc_first->tx_width);
-               if (atchan->remain_desc < 0) {
+
+               count = (desc_cur->lli.ctrla & ATC_BTSIZE_MAX)
+                       << (desc_first->tx_width);
+               if (atchan->remain_desc < count) {
                        ret = -EINVAL;
                        goto out;
-               } else {
-                       ret = atchan->remain_desc;
                }
+
+               atchan->remain_desc -= count;
+               ret = atchan->remain_desc;
        } else {
                /*
                 * Get residual bytes when current
-- 
1.9.1

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