drm/panthor: Explicitly set the coherency mode

This commit fixes the potential misalignment between the value of device
tree property "dma-coherent" and default value of COHERENCY_ENABLE
register.
Panthor driver didn't explicitly program the COHERENCY_ENABLE register
with the desired coherency mode. The default value of COHERENCY_ENABLE
register is implementation defined, so it may not be always aligned with
the "dma-coherent" property value.
The commit also checks the COHERENCY_FEATURES register to confirm that
the coherency protocol is actually supported or not.

v2:
- Added R-b tags

Signed-off-by: Akash Goel <akash.goel@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20241030225407.4077513-3-akash.goel@arm.com
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index 4082c8f2951dfdace7f73a24d6fe34e9e7f920eb..984615f4ed274597e8b3e55d67857f2b2d0fc265 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -22,6 +22,24 @@
 #include "panthor_regs.h"
 #include "panthor_sched.h"
 
+static int panthor_gpu_coherency_init(struct panthor_device *ptdev)
+{
+       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, GPU_COHERENCY_FEATURES) &
+                     GPU_COHERENCY_PROT_BIT(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);
@@ -156,7 +174,9 @@ int panthor_device_init(struct panthor_device *ptdev)
        struct page *p;
        int ret;
 
-       ptdev->coherent = device_get_dma_attr(ptdev->base.dev) == DEV_DMA_COHERENT;
+       ret = panthor_gpu_coherency_init(ptdev);
+       if (ret)
+               return ret;
 
        init_completion(&ptdev->unplug.done);
        ret = drmm_mutex_init(&ptdev->base, &ptdev->unplug.lock);

diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
index 2d3529a0b156c1c60ec9218a1ddd38646360f424..0f3cac6ec88e7bf154428a049e400032f12d4f80 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_gpu.c
+++ b/drivers/gpu/drm/panthor/panthor_gpu.c
@@ -77,6 +77,12 @@ static const struct panthor_model gpu_models[] = {
         GPU_IRQ_RESET_COMPLETED | \
         GPU_IRQ_CLEAN_CACHES_COMPLETED)
 
+static void panthor_gpu_coherency_set(struct panthor_device *ptdev)
+{
+       gpu_write(ptdev, GPU_COHERENCY_PROTOCOL,
+               ptdev->coherent ? GPU_COHERENCY_PROT_BIT(ACE_LITE) : GPU_COHERENCY_NONE);
+}
+
 static void panthor_gpu_init_info(struct panthor_device *ptdev)
 {
        const struct panthor_model *model;
@@ -365,6 +371,9 @@ int panthor_gpu_l2_power_on(struct panthor_device *ptdev)
                              hweight64(ptdev->gpu_info.shader_present));
        }
 
+       /* Set the desired coherency mode before the power up of L2 */
+       panthor_gpu_coherency_set(ptdev);
+
        return panthor_gpu_power_on(ptdev, L2, 1, 20000);
 }