[PATCH 3/8] drm/panthor: Replace cross-component register accesses with helpers

Karunika Choo
2026-04-10T16:48:01Z

Stop reaching into other components' registers directly and route those
operations through the component that owns them.

Move the timestamp/coherency helpers into panthor_gpu, add a doorbell
helper, and update call sites accordingly. This keeps register knowledge
local to each block and avoids spreading cross-component register
accesses across the driver.

This is a preparatory cleanup for using per-component iomem bases.

Signed-off-by: Karunika Choo <karunika.choo@arm.com>
---
drivers/gpu/drm/panthor/panthor_device.c | 27 ----------------
drivers/gpu/drm/panthor/panthor_drv.c | 7 ++---
drivers/gpu/drm/panthor/panthor_fw.c | 15 ++++++---
drivers/gpu/drm/panthor/panthor_fw.h | 1 +
drivers/gpu/drm/panthor/panthor_gpu.c | 40 ++++++++++++++++++++++++
drivers/gpu/drm/panthor/panthor_gpu.h | 6 ++++
drivers/gpu/drm/panthor/panthor_pwr.c | 2 +-
drivers/gpu/drm/panthor/panthor_sched.c | 2 +-
8 files changed, 62 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index f876b13492ae..bd417d6ae8c0 100644
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -22,38 +22,11 @@
#include "panthor_fw_regs.h"
#include "panthor_gem.h"
#include "panthor_gpu.h"
-#include "panthor_gpu_regs.h"
#include "panthor_hw.h"
#include "panthor_mmu.h"
#include "panthor_pwr.h"
#include "panthor_sched.h"

-static int panthor_gpu_coherency_init(struct panthor_device *ptdev)
-{
- BUILD_BUG_ON(GPU_COHERENCY_NONE != DRM_PANTHOR_GPU_COHERENCY_NONE);
- BUILD_BUG_ON(GPU_COHERENCY_ACE_LITE != DRM_PANTHOR_GPU_COHERENCY_ACE_LITE);
- BUILD_BUG_ON(GPU_COHERENCY_ACE != DRM_PANTHOR_GPU_COHERENCY_ACE);
-
- /* Start with no coherency, and update it if the device is flagged coherent. */
- ptdev->gpu_info.selected_coherency = GPU_COHERENCY_NONE;
- ptdev->coherent = device_get_dma_attr(ptdev->base.dev) == DEV_DMA_COHERENT;
-
- if (!ptdev->coherent)
- return 0;
-
- /* Check if the ACE-Lite coherency protocol is actually supported by the GPU.
- * ACE protocol has never been supported for command stream frontend GPUs.
- */
- if ((gpu_read(ptdev->iomem, GPU_COHERENCY_FEATURES) &
- GPU_COHERENCY_PROT_BIT(ACE_LITE))) {
- ptdev->gpu_info.selected_coherency = GPU_COHERENCY_ACE_LITE;
- return 0;
- }
-
- drm_err(&ptdev->base, "Coherency not supported by the device");
- return -ENOTSUPP;
-}
-
static int panthor_clk_init(struct panthor_device *ptdev)
{
ptdev->clks.core = devm_clk_get(ptdev->base.dev, NULL);
diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index e63210b01e6e..8cd39e6c3f5c 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -34,7 +34,6 @@
#include "panthor_fw.h"
#include "panthor_gem.h"
#include "panthor_gpu.h"
-#include "panthor_gpu_regs.h"
#include "panthor_heap.h"
#include "panthor_mmu.h"
#include "panthor_sched.h"
@@ -839,7 +838,7 @@ static int panthor_query_timestamp_info(struct panthor_device *ptdev,
}

if (flags & DRM_PANTHOR_TIMESTAMP_GPU_OFFSET)
- arg->timestamp_offset = gpu_read64(ptdev->iomem, GPU_TIMESTAMP_OFFSET);
+ arg->timestamp_offset = panthor_gpu_get_timestap_offset(ptdev);
else
arg->timestamp_offset = 0;

@@ -854,7 +853,7 @@ static int panthor_query_timestamp_info(struct panthor_device *ptdev,
query_start_time = 0;

if (flags & DRM_PANTHOR_TIMESTAMP_GPU)
- arg->current_timestamp = gpu_read64_counter(ptdev->iomem, GPU_TIMESTAMP);
+ arg->current_timestamp = panthor_gpu_get_timestap(ptdev);
else
arg->current_timestamp = 0;

@@ -870,7 +869,7 @@ static int panthor_query_timestamp_info(struct panthor_device *ptdev,
}

if (flags & DRM_PANTHOR_TIMESTAMP_GPU_CYCLE_COUNT)
- arg->cycle_count = gpu_read64_counter(ptdev->iomem, GPU_CYCLE_COUNT);
+ arg->cycle_count = panthor_gpu_get_cycle_count(ptdev);
else
arg->cycle_count = 0;

diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
index 4704275b9c8f..1c13a4884201 100644
--- a/drivers/gpu/drm/panthor/panthor_fw.c
+++ b/drivers/gpu/drm/panthor/panthor_fw.c
@@ -1054,7 +1054,7 @@ static void panthor_fw_init_global_iface(struct panthor_device *ptdev)
GLB_CFG_POWEROFF_TIMER |
GLB_CFG_PROGRESS_TIMER);

- gpu_write(ptdev->iomem, CSF_DOORBELL(CSF_GLB_DOORBELL_ID), 1);
+ panthor_fw_ring_doorbell(ptdev, CSF_GLB_DOORBELL_ID);

/* Kick the watchdog. */
mod_delayed_work(ptdev->reset.wq, &ptdev->fw->watchdog.ping_work,
@@ -1156,7 +1156,7 @@ static void panthor_fw_halt_mcu(struct panthor_device *ptdev)
else
panthor_fw_update_reqs(glb_iface, req, GLB_HALT, GLB_HALT);

- gpu_write(ptdev->iomem, CSF_DOORBELL(CSF_GLB_DOORBELL_ID), 1);
+ panthor_fw_ring_doorbell(ptdev, CSF_GLB_DOORBELL_ID);
}

static bool panthor_fw_wait_mcu_halted(struct panthor_device *ptdev)
@@ -1400,6 +1400,11 @@ int panthor_fw_csg_wait_acks(struct panthor_device *ptdev, u32 csg_slot,
return ret;
}

+void panthor_fw_ring_doorbell(struct panthor_device *ptdev, u32 doorbell_id)
+{
+ gpu_write(ptdev->iomem, CSF_DOORBELL(doorbell_id), 1);
+}
+
/**
* panthor_fw_ring_csg_doorbells() - Ring command stream group doorbells.
* @ptdev: Device.
@@ -1413,8 +1418,8 @@ void panthor_fw_ring_csg_doorbells(struct panthor_device *ptdev, u32 csg_mask)
{
struct panthor_fw_global_iface *glb_iface = panthor_fw_get_glb_iface(ptdev);

- panthor_fw_toggle_reqs(glb_iface, doorbell_req, doorbell_ack, csg_mask);
- gpu_write(ptdev->iomem, CSF_DOORBELL(CSF_GLB_DOORBELL_ID), 1);
+ panthor_fw_toggle_reqs(glb_iface, doorbell_req, doorbell_ack, csg_mask);\
+ panthor_fw_ring_doorbell(ptdev, CSF_GLB_DOORBELL_ID);
}

static void panthor_fw_ping_work(struct work_struct *work)
@@ -1429,7 +1434,7 @@ static void panthor_fw_ping_work(struct work_struct *work)
return;

panthor_fw_toggle_reqs(glb_iface, req, ack, GLB_PING);
- gpu_write(ptdev->iomem, CSF_DOORBELL(CSF_GLB_DOORBELL_ID), 1);
+ panthor_fw_ring_doorbell(ptdev, CSF_GLB_DOORBELL_ID);

ret = panthor_fw_glb_wait_acks(ptdev, GLB_PING, &acked, 100);
if (ret) {
diff --git a/drivers/gpu/drm/panthor/panthor_fw.h b/drivers/gpu/drm/panthor/panthor_fw.h
index fbdc21469ba3..a99a9b6f4825 100644
--- a/drivers/gpu/drm/panthor/panthor_fw.h
+++ b/drivers/gpu/drm/panthor/panthor_fw.h
@@ -500,6 +500,7 @@ int panthor_fw_csg_wait_acks(struct panthor_device *ptdev, u32 csg_id, u32 req_m
int panthor_fw_glb_wait_acks(struct panthor_device *ptdev, u32 req_mask, u32 *acked,
u32 timeout_ms);

+void panthor_fw_ring_doorbell(struct panthor_device *ptdev, u32 doorbell_id);
void panthor_fw_ring_csg_doorbells(struct panthor_device *ptdev, u32 csg_slot);

struct panthor_kernel_bo *
diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
index fecc30747acf..ef0aca2b7532 100644
--- a/drivers/gpu/drm/panthor/panthor_gpu.c
+++ b/drivers/gpu/drm/panthor/panthor_gpu.c
@@ -427,3 +427,43 @@ void panthor_gpu_resume(struct panthor_device *ptdev)
panthor_hw_l2_power_on(ptdev);
}

+u64 panthor_gpu_get_timestap(struct panthor_device *ptdev)
+{
+ return gpu_read64_counter(ptdev->iomem, GPU_TIMESTAMP);
+}
+
+u64 panthor_gpu_get_timestap_offset(struct panthor_device *ptdev)
+{
+ return gpu_read64(ptdev->iomem, GPU_TIMESTAMP_OFFSET);
+}
+
+u64 panthor_gpu_get_cycle_count(struct panthor_device *ptdev)
+{
+ return gpu_read64_counter(ptdev->iomem, GPU_CYCLE_COUNT);
+}
+
+int panthor_gpu_coherency_init(struct panthor_device *ptdev)
+{
+ BUILD_BUG_ON(GPU_COHERENCY_NONE != DRM_PANTHOR_GPU_COHERENCY_NONE);
+ BUILD_BUG_ON(GPU_COHERENCY_ACE_LITE != DRM_PANTHOR_GPU_COHERENCY_ACE_LITE);
+ BUILD_BUG_ON(GPU_COHERENCY_ACE != DRM_PANTHOR_GPU_COHERENCY_ACE);
+
+ /* Start with no coherency, and update it if the device is flagged coherent. */
+ ptdev->gpu_info.selected_coherency = GPU_COHERENCY_NONE;
+ ptdev->coherent = device_get_dma_attr(ptdev->base.dev) == DEV_DMA_COHERENT;
+
+ if (!ptdev->coherent)
+ return 0;
+
+ /* Check if the ACE-Lite coherency protocol is actually supported by the GPU.
+ * ACE protocol has never been supported for command stream frontend GPUs.
+ */
+ if ((gpu_read(ptdev->iomem, GPU_COHERENCY_FEATURES) &
+ GPU_COHERENCY_PROT_BIT(ACE_LITE))) {
+ ptdev->gpu_info.selected_coherency = GPU_COHERENCY_ACE_LITE;
+ return 0;
+ }
+
+ drm_err(&ptdev->base, "Coherency not supported by the device");
+ return -ENOTSUPP;
+}
diff --git a/drivers/gpu/drm/panthor/panthor_gpu.h b/drivers/gpu/drm/panthor/panthor_gpu.h
index 12c263a39928..c22378e5ce48 100644
--- a/drivers/gpu/drm/panthor/panthor_gpu.h
+++ b/drivers/gpu/drm/panthor/panthor_gpu.h
@@ -54,4 +54,10 @@ int panthor_gpu_soft_reset(struct panthor_device *ptdev);
void panthor_gpu_power_changed_off(struct panthor_device *ptdev);
int panthor_gpu_power_changed_on(struct panthor_device *ptdev);

+u64 panthor_gpu_get_timestap(struct panthor_device *ptdev);
+u64 panthor_gpu_get_timestap_offset(struct panthor_device *ptdev);
+u64 panthor_gpu_get_cycle_count(struct panthor_device *ptdev);
+
+int panthor_gpu_coherency_init(struct panthor_device *ptdev);
+
#endif
diff --git a/drivers/gpu/drm/panthor/panthor_pwr.c b/drivers/gpu/drm/panthor/panthor_pwr.c
index 306592ff2227..aafb0c5c7d23 100644
--- a/drivers/gpu/drm/panthor/panthor_pwr.c
+++ b/drivers/gpu/drm/panthor/panthor_pwr.c
@@ -199,7 +199,7 @@ static int panthor_pwr_domain_wait_transition(struct panthor_device *ptdev, u32

static void panthor_pwr_debug_info_show(struct panthor_device *ptdev)
{
- drm_info(&ptdev->base, "GPU_FEATURES: 0x%016llx", gpu_read64(ptdev->iomem, GPU_FEATURES));
+ drm_info(&ptdev->base, "GPU_FEATURES: 0x%016llx", ptdev->gpu_info.gpu_features);
drm_info(&ptdev->base, "PWR_STATUS: 0x%016llx", gpu_read64(ptdev->iomem, PWR_STATUS));
drm_info(&ptdev->base, "L2_PRESENT: 0x%016llx", gpu_read64(ptdev->iomem, PWR_L2_PRESENT));
drm_info(&ptdev->base, "L2_PWRTRANS: 0x%016llx", gpu_read64(ptdev->iomem, PWR_L2_PWRTRANS));
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 70b8a22b3ed7..60e7b4e20a13 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -3373,7 +3373,7 @@ queue_run_job(struct drm_sched_job *sched_job)
if (resume_tick)
sched_resume_tick(ptdev);

- gpu_write(ptdev->iomem, CSF_DOORBELL(queue->doorbell_id), 1);
+ panthor_fw_ring_doorbell(ptdev, queue->doorbell_id);
if (!sched->pm.has_ref &&
!(group->blocked_queues & BIT(job->queue_idx))) {
pm_runtime_get(ptdev->base.dev);
--
2.43.0