ALSA: pcm: Add debug print on memory allocation failure

Add debug prints after calls of do_alloc_pages. One simplification would
be to move print into do_alloc_pages, however it would cause spam in
logs, as preallocate_pcm_pages loops over do_alloc_pages trying lower
values in case of failures.
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Link: https://lore.kernel.org/r/20210318160618.2504068-2-amadeuszx.slawinski@linux.intel.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_memory.c

@@ -176,6 +176,10 @@ static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
 					   substream->dma_buffer.dev.dev,
 					   size, &new_dmab) < 0) {
 				buffer->error = -ENOMEM;
+				pr_debug("ALSA pcmC%dD%d%c,%d:%s: cannot preallocate for size %zu\n",
+					 substream->pcm->card->number, substream->pcm->device,
+					 substream->stream ? 'c' : 'p', substream->number,
+					 substream->pcm->name, size);
 				return;
 			}
 			substream->buffer_bytes_max = size;
@@ -400,6 +404,10 @@ int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size)
 				   substream->dma_buffer.dev.dev,
 				   size, dmab) < 0) {
 			kfree(dmab);
+			pr_debug("ALSA pcmC%dD%d%c,%d:%s: cannot preallocate for size %zu\n",
+				 substream->pcm->card->number, substream->pcm->device,
+				 substream->stream ? 'c' : 'p', substream->number,
+				 substream->pcm->name, size);
 			return -ENOMEM;
 		}
 	}