On 7/2/21 11:23 AM, Raphael Gallais-Pou wrote:
Hello Marek,
Hi,
Sorry for the late answer.
No worries, take your time
On 6/30/21 2:35 AM, Marek Vasut wrote:
On 6/29/21 1:58 PM, Raphael GALLAIS-POU - foss wrote:
[...]
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -425,10 +425,17 @@ static void ltdc_crtc_atomic_enable(struct
drm_crtc *crtc,
{
struct ltdc_device *ldev = crtc_to_ltdc(crtc);
struct drm_device *ddev = crtc->dev;
+ int ret;
DRM_DEBUG_DRIVER("\n");
- pm_runtime_get_sync(ddev->dev);
+ if (!pm_runtime_active(ddev->dev)) {
+ ret = pm_runtime_get_sync(ddev->dev);
All these if (!pm_runtime_active()) then pm_runtime_get_sync() calls
look like workaround for some larger issue. Shouldn't the pm_runtime
do some refcounting on its own , so this shouldn't be needed ?
This problem purely comes from the driver internals, so I don't think it
is a workaround.
Because of the "ltdc_crtc_mode_set_nofb" function which does not have
any "symmetrical" call, such as enable/disable functions, there was two
calls to pm_runtime_get_sync against one call to pm_runtime_put_sync.
This instability resulted in the LTDC clocks being always enabled, even
when the peripheral was disabled. This could be seen in the clk_summary
as explained in the patch summary among other things.
By doing so, we first check if the clocks are not already activated, and
in that case we call pm_runtime_get_sync.
I just have to wonder, how come other drivers don't need these if
(!pm_runtime_active()) pm_runtime_get_sync() conditions. I think they
just get/put the runtime PM within a call itself, not across function
calls. Maybe that could be the right fix here too ?
