drm/bridge: dw-hdmi: Move vmalloc PCM buffer management into the driver

The dw-hdmi drm bridge driver is the only one who still uses the ALSA
vmalloc helper API functions.  A previous attempt to change the way of
buffer management wasn't taken for this legacy stuff, as we had little
chance for test and some risk of major breaking.
Instead, this patch moves the vmalloc buffer stuff into the dw-hdmi
driver code itself, so that we can drop them from ALSA core code
afterwards.

There should be no functional changes.

Link: https://lore.kernel.org/20191210154536.29819-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20240807152725.18948-2-tiwai@suse.de

drivers/gpu/drm/bridge/synopsys/dw-hdmi-ahb-audio.c

@@ -8,6 +8,7 @@
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/vmalloc.h>
 #include <drm/bridge/dw_hdmi.h>
 #include <drm/drm_edid.h>
 
@@ -388,15 +389,36 @@ static int dw_hdmi_close(struct snd_pcm_substream *substream)
 
 static int dw_hdmi_hw_free(struct snd_pcm_substream *substream)
 {
-	return snd_pcm_lib_free_vmalloc_buffer(substream);
+	struct snd_pcm_runtime *runtime = substream->runtime;
+
+	vfree(runtime->dma_area);
+	runtime->dma_area = NULL;
+	return 0;
 }
 
 static int dw_hdmi_hw_params(struct snd_pcm_substream *substream,
 	struct snd_pcm_hw_params *params)
 {
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	size_t size = params_buffer_bytes(params);
+
 	/* Allocate the PCM runtime buffer, which is exposed to userspace. */
-	return snd_pcm_lib_alloc_vmalloc_buffer(substream,
-						params_buffer_bytes(params));
+	if (runtime->dma_area) {
+		if (runtime->dma_bytes >= size)
+			return 0; /* already large enough */
+		vfree(runtime->dma_area);
+	}
+	runtime->dma_area = vzalloc(size);
+	if (!runtime->dma_area)
+		return -ENOMEM;
+	runtime->dma_bytes = size;
+	return 1;
+}
+
+static struct page *dw_hdmi_get_page(struct snd_pcm_substream *substream,
+				     unsigned long offset)
+{
+	return vmalloc_to_page(substream->runtime->dma_area + offset);
 }
 
 static int dw_hdmi_prepare(struct snd_pcm_substream *substream)
@@ -515,7 +537,7 @@ static const struct snd_pcm_ops snd_dw_hdmi_ops = {
 	.prepare = dw_hdmi_prepare,
 	.trigger = dw_hdmi_trigger,
 	.pointer = dw_hdmi_pointer,
-	.page = snd_pcm_lib_get_vmalloc_page,
+	.page = dw_hdmi_get_page,
 };
 
 static int snd_dw_hdmi_probe(struct platform_device *pdev)