[RFT PATCH 2/6] drm: Call drm_atomic_helper_shutdown() at shutdown time for misc drivers

[suijingfeng]

Hi,


On 2023/9/2 07:39, Douglas Anderson wrote:
> Based on grepping through the source code these drivers appear to be
> missing a call to drm_atomic_helper_shutdown() at system shutdown
> time. Among other things, this means that if a panel is in use that it
> won't be cleanly powered off at system shutdown time.
>
> The fact that we should call drm_atomic_helper_shutdown() in the case
> of OS shutdown/restart comes straight out of the kernel doc "driver
> instance overview" in drm_drv.c.
>
> All of the drivers in this patch were fairly straightforward to fix
> since they already had a call to drm_atomic_helper_shutdown() at
> remove/unbind time but were just lacking one at system shutdown. The
> only hitch is that some of these drivers use the component model to
> register/unregister their DRM devices. The shutdown callback is part
> of the original device. The typical solution here, based on how other
> DRM drivers do this, is to keep track of whether the device is bound
> based on drvdata. In most cases the drvdata is the drm_device, so we
> can just make sure it is NULL when the device is not bound. In some
> drivers, this required minor code changes. To make things simpler,
> drm_atomic_helper_shutdown() has been modified to consider a NULL
> drm_device as a noop in the patch ("drm/atomic-helper:
> drm_atomic_helper_shutdown(NULL) should be a noop").
>
> Suggested-by: Maxime Ripard <mripard at kernel.org>
> Signed-off-by: Douglas Anderson <dianders at chromium.org>
> ---


I have just tested the whole series, thanks for the patch. For drm/loongson only:


Reviewed-by: Sui Jingfeng <suijingfeng at loongson.cn>
Tested-by: Sui Jingfeng <suijingfeng at loongson.cn>



By the way, I add 'pr_info("lsdc_pci_shutdown\n");' into the lsdc_pci_shutdown() function,
And seeing that lsdc_pci_shutdown() will be called when reboot and shutdown the machine.
I did not witness something weird happen at present. As you have said, this is useful for
drm panels drivers. But for the rest(drm/hibmc, drm/ast, drm/mgag200 and drm/loongson etc)
drivers, you didn't mention what's the benefit for those drivers. Probably, you can
mention it with at least one sentence at the next version. I also prefer to alter the
lsdc_pci_shutdown() function as the following pattern:


static void lsdc_pci_shutdown(struct pci_dev *pdev)
{

     struct drm_device *ddev = pci_get_drvdata(pdev);

     drm_atomic_helper_shutdown(ddev);
}