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To:     KuoHsiang Chou <kuohsiang_chou@aspeedtech.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Cc:     airlied@redhat.com, airlied@linux.ie, daniel@ffwll.ch,
        jenmin_yuan@aspeedtech.com, arc_sung@aspeedtech.com
References: <bbe8ccfd-7e73-e1e6-32a5-f08f71c4ed3f@suse.de>
 <20210507092708.39552-1-kuohsiang_chou@aspeedtech.com>
From:   Thomas Zimmermann <tzimmermann@suse.de>
Subject: Re: [PATCH v4] drm/ast: Disable fast reset after DRAM initial
Message-ID: <bb505d06-bf46-237c-ed2f-15e3f23ec338@suse.de>
Date:   Wed, 23 Jun 2021 10:02:58 +0200
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From: Thomas Zimmermann <tzimmermann@suse.de>
To: KuoHsiang Chou <kuohsiang_chou@aspeedtech.com>,
 dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Cc: airlied@redhat.com, airlied@linux.ie, daniel@ffwll.ch,
 jenmin_yuan@aspeedtech.com, arc_sung@aspeedtech.com
Message-ID: <bb505d06-bf46-237c-ed2f-15e3f23ec338@suse.de>
Subject: Re: [PATCH v4] drm/ast: Disable fast reset after DRAM initial
References: <bbe8ccfd-7e73-e1e6-32a5-f08f71c4ed3f@suse.de>
 <20210507092708.39552-1-kuohsiang_chou@aspeedtech.com>
In-Reply-To: <20210507092708.39552-1-kuohsiang_chou@aspeedtech.com>

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Hi,

here's the review that you've been waiting for. Sorry for taking so long.=


Am 07.05.21 um 11:27 schrieb KuoHsiang Chou:
> [Bug][AST2500]
>=20
> V1:
> When AST2500 acts as stand-alone VGA so that DRAM and DVO initializatio=
n
> have to be achieved by VGA driver with P2A (PCI to AHB) enabling.
> However, HW suggests disable Fast reset mode after DRAM initializaton,
> because fast reset mode is mainly designed for ARM ICE debugger.
> Once Fast reset is checked as enabling, WDT (Watch Dog Timer) should be=

> first enabled to avoid system deadlock before disable fast reset mode.
>=20
> V2:
> Use to_pci_dev() to get revision of PCI configuration.
>=20
> V3:
> If SCU00 is not unlocked, just enter its password again.
> It is unnecessary to clear AHB lock condition and restore WDT default
> setting again, before Fast-reset clearing.
>=20
> V4:
> repatch after "error : could not build fake ancestor" resolved.
>=20
> Signed-off-by: KuoHsiang Chou <kuohsiang_chou@aspeedtech.com>
> ---
>   drivers/gpu/drm/ast/ast_drv.h  |  1 +
>   drivers/gpu/drm/ast/ast_main.c |  4 ++
>   drivers/gpu/drm/ast/ast_post.c | 68 +++++++++++++++++++++------------=
-
>   3 files changed, 47 insertions(+), 26 deletions(-)
>=20
> diff --git a/drivers/gpu/drm/ast/ast_drv.h b/drivers/gpu/drm/ast/ast_dr=
v.h
> index 911f9f414..5ebb5905d 100644
> --- a/drivers/gpu/drm/ast/ast_drv.h
> +++ b/drivers/gpu/drm/ast/ast_drv.h
> @@ -346,6 +346,7 @@ bool ast_is_vga_enabled(struct drm_device *dev);
>   void ast_post_gpu(struct drm_device *dev);
>   u32 ast_mindwm(struct ast_private *ast, u32 r);
>   void ast_moutdwm(struct ast_private *ast, u32 r, u32 v);
> +void ast_patch_ahb_2500(struct ast_private *ast);
>   /* ast dp501 */
>   void ast_set_dp501_video_output(struct drm_device *dev, u8 mode);
>   bool ast_backup_fw(struct drm_device *dev, u8 *addr, u32 size);
> diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_m=
ain.c
> index 2aff2e6cf..cfb56ea3a 100644
> --- a/drivers/gpu/drm/ast/ast_main.c
> +++ b/drivers/gpu/drm/ast/ast_main.c
> @@ -97,6 +97,10 @@ static void ast_detect_config_mode(struct drm_device=
 *dev, u32 *scu_rev)
>   	jregd0 =3D ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xd0, 0xff)=
;
>   	jregd1 =3D ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xd1, 0xff)=
;
>   	if (!(jregd0 & 0x80) || !(jregd1 & 0x10)) {
> +		/* Patch AST2500 */
> +		if (((pdev->revision & 0xF0) =3D=3D 0x40) && ((jregd0 & 0xC0) =3D=3D=
 0))

These magic numbers are hard to read. Is there any way of make it more=20
clear what we're testing for? Constants? Helper functions?

> +			ast_patch_ahb_2500(ast);
> +
>   		/* Double check it's actually working */
>   		data =3D ast_read32(ast, 0xf004);
>   		if ((data !=3D 0xFFFFFFFF) && (data !=3D 0x00)) {
> diff --git a/drivers/gpu/drm/ast/ast_post.c b/drivers/gpu/drm/ast/ast_p=
ost.c
> index 0607658dd..56428798a 100644
> --- a/drivers/gpu/drm/ast/ast_post.c
> +++ b/drivers/gpu/drm/ast/ast_post.c
> @@ -2028,6 +2028,30 @@ static bool ast_dram_init_2500(struct ast_privat=
e *ast)
>   	return true;
>   }
>=20
> +void ast_patch_ahb_2500(struct ast_private *ast)
> +{
> +	u32	data;

Only a single space after the type.

> +
> +	/* Clear bus lock condition */
> +	ast_moutdwm(ast, 0x1e600000, 0xAEED1A03);
> +	ast_moutdwm(ast, 0x1e600084, 0x00010000);
> +	ast_moutdwm(ast, 0x1e600088, 0x00000000);
> +	ast_moutdwm(ast, 0x1e6e2000, 0x1688A8A8);
> +	data =3D ast_mindwm(ast, 0x1e6e2070);
> +	if (data & 0x08000000) {					/* check fast reset */
> +

No empty line here.

> +		ast_moutdwm(ast, 0x1E785004, 0x00000010);
> +		ast_moutdwm(ast, 0x1E785008, 0x00004755);
> +		ast_moutdwm(ast, 0x1E78500c, 0x00000033);
> +		udelay(1000);
> +	}
> +	do {
> +		ast_moutdwm(ast, 0x1e6e2000, 0x1688A8A8);
> +		data =3D ast_mindwm(ast, 0x1e6e2000);
> +	}	while (data !=3D 1);
> +	ast_moutdwm(ast, 0x1e6e207c, 0x08000000);	/* clear fast reset */
> +}
> +
>   void ast_post_chip_2500(struct drm_device *dev)
>   {
>   	struct ast_private *ast =3D to_ast_private(dev);
> @@ -2035,39 +2059,31 @@ void ast_post_chip_2500(struct drm_device *dev)=

>   	u8 reg;
>=20
>   	reg =3D ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xd0, 0xff);
> -	if ((reg & 0x80) =3D=3D 0) {/* vga only */
> +	if ((reg & 0xC0) =3D=3D 0) {/* vga only */

Why this change?

>   		/* Clear bus lock condition */
> -		ast_moutdwm(ast, 0x1e600000, 0xAEED1A03);
> -		ast_moutdwm(ast, 0x1e600084, 0x00010000);
> -		ast_moutdwm(ast, 0x1e600088, 0x00000000);
> -		ast_moutdwm(ast, 0x1e6e2000, 0x1688A8A8);
> -		ast_write32(ast, 0xf004, 0x1e6e0000);
> -		ast_write32(ast, 0xf000, 0x1);
> -		ast_write32(ast, 0x12000, 0x1688a8a8);
> -		while (ast_read32(ast, 0x12000) !=3D 0x1)
> -			;
> -
> -		ast_write32(ast, 0x10000, 0xfc600309);
> -		while (ast_read32(ast, 0x10000) !=3D 0x1)
> -			;
> +		ast_patch_ahb_2500(ast);

You're calling this function here, but it's different from the old code.

> +
> +		/* Disable watchdog */
> +		ast_moutdwm(ast, 0x1E78502C, 0x00000000);
> +		ast_moutdwm(ast, 0x1E78504C, 0x00000000);
> +		/* Reset USB port */

Reset USB port? In the graphics driver?


The whole gpu post/init code is undecipherable to me. It's full of magic =

numbers that are nowhere documented.


Therefore, the overall problem with this patch is that I have no idea=20
what the actual bug fix is.
  Is it possible to first refactor that code a bit and then add a=20
minimal fix?

Best regards
Thomas


--=20
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 N=C3=BCrnberg, Germany
(HRB 36809, AG N=C3=BCrnberg)
Gesch=C3=A4ftsf=C3=BChrer: Felix Imend=C3=B6rffer


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