Re: [PATCH 2/9] drm/rockchip: vop2: Reset AXI and DCLK to improve robustness

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

On 6/18/26 12:39 PM, Philipp Zabel wrote:
> On Mi, 2026-06-17 at 21:51 +0300, Cristian Ciocaltea wrote:
>> Assert the AXI reset in the CRTC disable path, and the VP DCLK reset in
>> the enable path.
>>
>> These resets are intended to leave the hardware in a clean state for the
>> next use, helping recover from exceptions such as IOMMU page faults, as
>> well as to prevent random display output glitches, such as a blank
>> image, observed when switching modes that also change the color format,
>> e.g. from RGB to YUV420 and vice versa.
>>
>> For now this seems to affect only the RK3588, hence the resets are
>> optional and will be provided in the device tree for this SoC only.
>>
>> Co-developed-by: Andy Yan <andy.yan@rock-chips.com>
>> Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
>> ---
>>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 35 ++++++++++++++++++++++++++++
>>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.h |  4 ++++
>>  2 files changed, 39 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> index 4cce3e336f5b..2833fb49ad81 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
>> @@ -17,6 +17,7 @@
>>  #include <linux/platform_device.h>
>>  #include <linux/pm_runtime.h>
>>  #include <linux/regmap.h>
>> +#include <linux/reset.h>
>>  #include <linux/swab.h>
>>  
>>  #include <drm/drm.h>
>> @@ -860,6 +861,26 @@ static int vop2_core_clks_prepare_enable(struct vop2 *vop2)
>>  	return ret;
>>  }
>>  
>> +static void vop2_clk_reset(struct vop2 *vop2, struct reset_control *rstc)
> 
> The _clk part of the function name is misleading ...

Ack.  

We need to make this clearly distinct from another similarly named function,
vop2_crtc_reset(), hence I'd propose:

- vop2_reset_assert_deassert()
- vop2_reset_cycle()
- vop2_do_reset()

Any preference / alternative suggestions?

> 
> [...]
>> @@ -938,6 +959,8 @@ static void vop2_disable(struct vop2 *vop2)
>>  {
>>  	rockchip_drm_dma_detach_device(vop2->drm, vop2->dev);
>>  
>> +	vop2_clk_reset(vop2, vop2->axi_rst);
> 
> ... because this function is also called with the AXI reset control.
> 
>> +
>>  	pm_runtime_put_sync(vop2->dev);
>>  
>>  	regcache_drop_region(vop2->map, 0, vop2_regmap_config.max_register);
>> @@ -1948,6 +1971,8 @@ static void vop2_crtc_atomic_enable(struct drm_crtc *crtc,
>>  
>>  	vop2_crtc_atomic_try_set_gamma(vop2, vp, crtc, crtc_state);
>>  
>> +	vop2_clk_reset(vop2, vp->dclk_rst);
>> +
>>  	drm_crtc_vblank_on(crtc);
>>  
>>  	vop2_unlock(vop2);
>> @@ -2531,6 +2556,11 @@ static int vop2_create_crtcs(struct vop2 *vop2)
>>  			return dev_err_probe(drm->dev, PTR_ERR(vp->dclk),
>>  					     "failed to get %s\n", dclk_name);
>>  
>> +		vp->dclk_rst = devm_reset_control_get_optional(vop2->dev, dclk_name);
> 
> Please use devm_reset_control_get_optional_exclusive() directly.

Thanks for pointing this out, I missed the comment mentioning the explicit API
transition.

>> +		if (IS_ERR(vp->dclk_rst))
>> +			return dev_err_probe(drm->dev, PTR_ERR(vp->dclk_rst),
>> +					     "failed to get %s reset\n", dclk_name);
>> +
>>  		np = of_graph_get_remote_node(dev->of_node, i, -1);
>>  		if (!np) {
>>  			drm_dbg(vop2->drm, "%s: No remote for vp%d\n", __func__, i);
>> @@ -2890,6 +2920,11 @@ static int vop2_bind(struct device *dev, struct device *master, void *data)
>>  		return dev_err_probe(drm->dev, PTR_ERR(vop2->pll_hdmiphy1),
>>  				     "failed to get pll_hdmiphy1\n");
>>  
>> +	vop2->axi_rst = devm_reset_control_get_optional(vop2->dev, "axi");
> 
> Same as above, devm_reset_control_get_optional_exclusive().

Ack.

Thanks for reviewing,
Cristian