fridtjof/qemu-cr16
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

esp.c: only call dma_memory_write function if transfer length is non-zero

Browse source 
In the cases where mixed DMA/non-DMA transfers are used or no data is
available, it is possible for the calculated transfer length to be zero.
Only call the dma_memory_write function where the transfer length is
non-zero to avoid invoking the DMA engine for a zero length transfer
which can have side-effects (along with generating additional tracing
noise).

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250711204636.542964-6-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
This commit is contained in:
Mark Cave-Ayland 2025-07-11 21:46:34 +01:00 • committed by Philippe Mathieu-Daudé
parent 9d6df740ec
commit 28a579a349
1 changed files with 5 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

6
hw/scsi/esp.c
View file

@ -631,7 +631,9 @@ static void esp_do_dma(ESPState *s)
switch (s->rregs[ESP_CMD]) {
case CMD_TI | CMD_DMA:
if (s->dma_memory_write) {
s->dma_memory_write(s->dma_opaque, s->async_buf, len);
if (len) {
s->dma_memory_write(s->dma_opaque, s->async_buf, len);
}
} else {
/* Copy device data to FIFO */
len = MIN(len, fifo8_num_free(&s->fifo));
@ -681,6 +683,7 @@ static void esp_do_dma(ESPState *s)
buf[0] = s->status;
if (s->dma_memory_write) {
/* Length already non-zero */
s->dma_memory_write(s->dma_opaque, buf, len);
} else {
esp_fifo_push_buf(s, buf, len);
@ -715,6 +718,7 @@ static void esp_do_dma(ESPState *s)
buf[0] = 0;
if (s->dma_memory_write) {
/* Length already non-zero */
s->dma_memory_write(s->dma_opaque, buf, len);
} else {
esp_fifo_push_buf(s, buf, len);