2 files changed, 14 insertions, 7 deletions

diff --git a/device_info_procfs.c b/device_info_procfs.c
index 0229eec..4e4ab03 100644
--- a/device_info_procfs.c
+++ b/device_info_procfs.c
@@ -20,7 +20,7 @@ static ssize_t nvdebug_reg32_read(struct file *f, char __user *buf, size_t size,
         if ((read = nvdebug_readl(g, (uintptr_t)pde_data(file_inode(f)))) == -1)
                 return -EOPNOTSUPP;
         // 32 bit register will always take less than 16 characters to print
-        chars_written = scnprintf(out, 16, "%#0x\n", nvdebug_readl(g, read));
+        chars_written = scnprintf(out, 16, "%#0x\n", read);
         if (copy_to_user(buf, out, chars_written))
                 printk(KERN_WARNING "[nvdebug] %s: Unable to copy all data for %s\n", __func__, file_dentry(f)->d_name.name);
         *off += chars_written;
diff --git a/nvdebug_linux.c b/nvdebug_linux.c
index 111d5aa..e673a8b 100644
--- a/nvdebug_linux.c
+++ b/nvdebug_linux.c
@@ -1,4 +1,4 @@
-/* Copyright 2024 Joshua Bakita
+/* Copyright 2024-2025 Joshua Bakita
  * Implementation of Kernel-specific function implementations
  */
 #include "nvdebug_linux.h"
@@ -9,10 +9,14 @@ u32 nvdebug_readl(struct nvdebug_state *s, u32 r) {
         u32 ret;
         // If this is an integrated ("platform") GPU, make sure that it's on first
         // (pm_runtime_enabled() will return false until nvgpu is started. Once
-        // nvgpu is started, pm_runtime_get() will attempt to resume the GPU.)
+        // nvgpu is started, pm_runtime_get_sync() will attempt to resume the GPU.
+        // This still increments the usage counter on failure, so we undo that with
+        // pm_runtime_put_noidle(). We avoid pm_runtime_resume_and_get() as it was
+        // not added until Linux 5.9.11)
         // This works to bring up the TX2, Xavier, and Orin, but not the TX1.
-        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get(s->dev) < 0)) {
+        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
                 printk(KERN_ERR "[nvdebug] nvdebug_readl: Unable to read; registers unavailable. Is GPU on?\n");
+                pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
                 return -1;
         }
         ret = readl(s->regs + r);
@@ -39,8 +43,9 @@ u32 nvdebug_readl(struct nvdebug_state *s, u32 r) {
 u64 nvdebug_readq(struct nvdebug_state *s, u32 r) {
         u64 ret;
         // If this is an integrated ("platform") GPU, make sure that it's on first
-        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get(s->dev) < 0)) {
+        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
                 printk(KERN_ERR "[nvdebug] nvdebug_readq: Unable to read; registers unavailable. Is GPU on?\n");
+                pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
                 return -1;
         }
         // readq seems to always (?) return the uppermost 32 bits as 0, so workaround with readl
@@ -59,8 +64,9 @@ u64 nvdebug_readq(struct nvdebug_state *s, u32 r) {
 
 void nvdebug_writel(struct nvdebug_state *s, u32 r, u32 v) {
         // If this is an integrated ("platform") GPU, make sure that it's on first
-        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get(s->dev) < 0)) {
+        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
                 printk(KERN_ERR "[nvdebug] nvdebug_writel: Unable to write; registers unavailable. Is GPU on?\n");
+                pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
                 return;
         }
         writel_relaxed(v, s->regs + r);
@@ -74,8 +80,9 @@ void nvdebug_writel(struct nvdebug_state *s, u32 r, u32 v) {
 // XXX: Not clear this works on all platforms
 void nvdebug_writeq(struct nvdebug_state *s, u32 r, u64 v) {
         // If this is an integrated ("platform") GPU, make sure that it's on first
-        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get(s->dev) < 0)) {
+        if (s->platd && (!pm_runtime_enabled(s->dev) || pm_runtime_get_sync(s->dev) < 0)) {
                 printk(KERN_ERR "[nvdebug] nvdebug_writeq: Unable to write; registers unavailable. Is GPU on?\n");
+                pm_runtime_put_noidle(s->dev); // No-op if !pm_runtime_enabled()
                 return;
         }
         writeq_relaxed(v, s->regs + r);