linux-kernel - Re: [PATCH] drm/imagination: properly support stopping LAYOUT

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Message-ID: <8e024981-c531-498e-8ae1-b20f0773f112@imgtec.com>
Date: Mon, 2 Sep 2024 09:24:29 +0000
From: Matt Coster <Matt.Coster@...tec.com>
To: Icenowy Zheng <uwu@...nowy.me>,
        "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: Frank Binns <Frank.Binns@...tec.com>,
        Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/imagination: properly support stopping LAYOUT_MARS =
 1 cores

On 11/08/2024 09:28, Icenowy Zheng wrote:
> Some new Rogue GPU cores have an extra MARS power domain, which
> controlls the power of the firmware core and allows the firmware core to
> power down most parts of the GPU.
> 
> Adapt to this by ignoring power domains that should be powered down by
> the fiwmare and checking MARS idle status instead.
> 
> The logic mimics RGXStop() function in the DDK kernel mode source code.
> 
> Tested on BXE-4-32 (36.50.54.182) with firmware build 6503725 OS provided
> by Imagination Technologies.
> 
> Signed-off-by: Icenowy Zheng <uwu@...nowy.me>

Hi Icenowy,

Thanks for the patch! It's great to see people getting involved in
getting this driver working on more platforms. 

> ---
>  .../gpu/drm/imagination/pvr_fw_startstop.c    | 49 +++++++++++++------
>  1 file changed, 35 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imagination/pvr_fw_startstop.c b/drivers/gpu/drm/imagination/pvr_fw_startstop.c
> index 159a4c3dd65b..4301a7aded64 100644
> --- a/drivers/gpu/drm/imagination/pvr_fw_startstop.c
> +++ b/drivers/gpu/drm/imagination/pvr_fw_startstop.c
> @@ -201,19 +201,28 @@ pvr_fw_stop(struct pvr_device *pvr_dev)
>  				       ~(ROGUE_CR_SIDEKICK_IDLE_GARTEN_EN |
>  					 ROGUE_CR_SIDEKICK_IDLE_SOCIF_EN |
>  					 ROGUE_CR_SIDEKICK_IDLE_HOSTIF_EN);
> +	const u32 mars_idle_mask = ROGUE_CR_MARS_IDLE_CPU_EN |
> +				   ROGUE_CR_MARS_IDLE_MH_SYSARB0_EN;
>  	bool skip_garten_idle = false;
> +	u32 mars = 0;
>  	u32 reg_value;
>  	int err;
>  
> +	if (PVR_HAS_FEATURE(pvr_dev, layout_mars))
> +		PVR_FEATURE_VALUE(pvr_dev, layout_mars, &mars);
> +

This check is unnecessary – the PVR_FEATURE_VALUE() macro already checks
for the feature presence internally and doesn't change the output value
if it's not present. 

>  	/*
>  	 * Wait for Sidekick/Jones to signal IDLE except for the Garten Wrapper.
>  	 * For cores with the LAYOUT_MARS feature, SIDEKICK would have been
>  	 * powered down by the FW.
>  	 */
> -	err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_SIDEKICK_IDLE, sidekick_idle_mask,
> -				sidekick_idle_mask, POLL_TIMEOUT_USEC);
> -	if (err)
> -		return err;
> +	if (mars) {

I think you might have these conditionals backwards. This is saying we
need to touch sidekick iff mars is present, but the comments say this is
the other way around (mars takes care of powering sidekick, so we don't
need to).

Cheers,
Matt 

> +		err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_SIDEKICK_IDLE,
> +					sidekick_idle_mask,
> +					sidekick_idle_mask, POLL_TIMEOUT_USEC);
> +		if (err)
> +			return err;
> +	}
>  
>  	/* Unset MTS DM association with threads. */
>  	pvr_cr_write32(pvr_dev, ROGUE_CR_MTS_INTCTX_THREAD0_DM_ASSOC,
> @@ -267,21 +276,27 @@ pvr_fw_stop(struct pvr_device *pvr_dev)
>  	 * For cores with the LAYOUT_MARS feature, SLC would have been powered
>  	 * down by the FW.
>  	 */
> -	err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_SLC_IDLE,
> -				ROGUE_CR_SLC_IDLE_MASKFULL,
> -				ROGUE_CR_SLC_IDLE_MASKFULL, POLL_TIMEOUT_USEC);
> -	if (err)
> -		return err;
> +	if (mars) {
> +		err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_SLC_IDLE,
> +					ROGUE_CR_SLC_IDLE_MASKFULL,
> +					ROGUE_CR_SLC_IDLE_MASKFULL,
> +					POLL_TIMEOUT_USEC);
> +		if (err)
> +			return err;
> +	}
>  
>  	/*
>  	 * Wait for Sidekick/Jones to signal IDLE except for the Garten Wrapper.
>  	 * For cores with the LAYOUT_MARS feature, SIDEKICK would have been powered
>  	 * down by the FW.
>  	 */
> -	err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_SIDEKICK_IDLE, sidekick_idle_mask,
> -				sidekick_idle_mask, POLL_TIMEOUT_USEC);
> -	if (err)
> -		return err;
> +	if (mars) {
> +		err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_SIDEKICK_IDLE,
> +					sidekick_idle_mask,
> +					sidekick_idle_mask, POLL_TIMEOUT_USEC);
> +		if (err)
> +			return err;
> +	}
>  
>  	if (pvr_dev->fw_dev.processor_type == PVR_FW_PROCESSOR_TYPE_META) {
>  		err = pvr_meta_cr_read32(pvr_dev, META_CR_TxVECINT_BHALT, &reg_value);
> @@ -297,7 +312,13 @@ pvr_fw_stop(struct pvr_device *pvr_dev)
>  			skip_garten_idle = true;
>  	}
>  
> -	if (!skip_garten_idle) {
> +	if (mars) {
> +		err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_MARS_IDLE,
> +					mars_idle_mask, mars_idle_mask,
> +					POLL_TIMEOUT_USEC);
> +		if (err)
> +			return err;
> +	} else if (!skip_garten_idle) {
>  		err = pvr_cr_poll_reg32(pvr_dev, ROGUE_CR_SIDEKICK_IDLE,
>  					ROGUE_CR_SIDEKICK_IDLE_GARTEN_EN,
>  					ROGUE_CR_SIDEKICK_IDLE_GARTEN_EN,


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