[PATCH v7 15/19] media: meson: vdec: Fix concurrent firmware loading race and hardware timeout

[Anand Moon <linux.amoon@gmail.com>]

The vdec_1 firmware loader used static variables for DMA buffer
addresses (`mc_addr`, `mc_addr_map`). This made allocations global
across sessions, corrupting state when multiple decoders loaded
firmware concurrently. Under stress this triggered KASAN reports,
lost references, and memory leaks. Making mc_addr and mc_addr_map
local to each load call, eliminating cross‑session races.

The firmware DMA completion check also relied on a raw decrement
loop of 1000 iterations. On modern CPUs this loop completed far
too quickly, often before hardware signaled ready, producing
false "DMA hang" errors. Replacing the busy‑wait loop with
readl_poll_timeout_atomic(),  providing a bounded, microsecond
scale poll with proper timeout semantics.

Cc: Nicolas Dufresne <nicolas@ndufresne.ca>
Signed-off-by: Anand Moon <linux.amoon@gmail.com>
---
 drivers/staging/media/meson/vdec/vdec_1.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/media/meson/vdec/vdec_1.c b/drivers/staging/media/meson/vdec/vdec_1.c
index a65cb49594465..27363c9a5af3c 100644
--- a/drivers/staging/media/meson/vdec/vdec_1.c
+++ b/drivers/staging/media/meson/vdec/vdec_1.c
@@ -29,14 +29,14 @@ vdec_1_load_firmware(struct amvdec_session *sess, const char *fwname)
 	struct amvdec_core *core = sess->core;
 	struct device *dev = core->dev_dec;
 	struct amvdec_codec_ops *codec_ops = sess->fmt_out->codec_ops;
-	static void *mc_addr;
-	static dma_addr_t mc_addr_map;
+	void *mc_addr;
+	dma_addr_t mc_addr_map;
 	int ret;
-	u32 i = 1000;
+	u32 val;
 
 	ret = request_firmware(&fw, fwname, dev);
 	if (ret < 0)
-		return -EINVAL;
+		return ret;
 
 	if (fw->size < MC_SIZE) {
 		dev_err(dev, "Firmware size %zu is too small. Expected %u.\n",
@@ -63,11 +63,11 @@ vdec_1_load_firmware(struct amvdec_session *sess, const char *fwname)
 	amvdec_write_dos(core, IMEM_DMA_COUNT, MC_SIZE / 4);
 	amvdec_write_dos(core, IMEM_DMA_CTRL, (0x8000 | (7 << 16)));
 
-	while (--i && amvdec_read_dos(core, IMEM_DMA_CTRL) & 0x8000);
-
-	if (i == 0) {
+	ret = readl_poll_timeout_atomic(core->dos_base + IMEM_DMA_CTRL, val,
+					!(val & 0x8000), 10, 10000);
+	if (ret) {
 		dev_err(dev, "Firmware load fail (DMA hang?)\n");
-		ret = -EINVAL;
+		ret = -ETIMEDOUT;
 		goto free_mc;
 	}
 
-- 
2.50.1