linux-kernel - Re: [PATCH v25 07/10] soc: mediatek: mmsys: add mmsys for support 64 reset bits

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Message-ID: <20220819142522.c4o3nrkxfj2r3zd7@notapiano>
Date:   Fri, 19 Aug 2022 10:25:22 -0400
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     "Nancy.Lin" <nancy.lin@...iatek.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>, wim@...ux-watchdog.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, linux@...ck-us.net,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "jason-jh . lin" <jason-jh.lin@...iatek.com>,
        Yongqiang Niu <yongqiang.niu@...iatek.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, llvm@...ts.linux.dev,
        singo.chang@...iatek.com,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v25 07/10] soc: mediatek: mmsys: add mmsys for support 64
 reset bits

On Fri, Aug 19, 2022 at 12:13:23PM +0800, Nancy.Lin wrote:
> Hi Nicolas,
> 
> 
> On Fri, 2022-08-19 at 10:09 +0800, Nancy.Lin wrote:
> > Hi Nicolas,
> > 
> > Thanks for the review.
> > 
> > On Thu, 2022-08-18 at 17:47 -0400, Nícolas F. R. A. Prado wrote:
> > > Hi Nancy,
> > > 
> > > On Mon, Jul 11, 2022 at 03:52:42PM +0800, Nancy.Lin wrote:
> > > [..]
> > > >  static const struct mtk_mmsys_driver_data
> > > > mt2701_mmsys_driver_data
> > > > = {
> > > >  	.clk_driver = "clk-mt2701-mm",
> > > >  	.routes = mmsys_default_routing_table,
> > > > @@ -86,6 +88,7 @@ static const struct mtk_mmsys_driver_data
> > > > mt8173_mmsys_driver_data = {
> > > >  	.routes = mmsys_default_routing_table,
> > > >  	.num_routes = ARRAY_SIZE(mmsys_default_routing_table),
> > > >  	.sw0_rst_offset = MT8183_MMSYS_SW0_RST_B,
> > > > +	.num_resets = 32,
> > > >  };
> > > >  
> > > >  static const struct mtk_mmsys_match_data mt8173_mmsys_match_data
> > > > =
> > > > {
> > > > @@ -100,6 +103,7 @@ static const struct mtk_mmsys_driver_data
> > > > mt8183_mmsys_driver_data = {
> > > >  	.routes = mmsys_mt8183_routing_table,
> > > >  	.num_routes = ARRAY_SIZE(mmsys_mt8183_routing_table),
> > > >  	.sw0_rst_offset = MT8183_MMSYS_SW0_RST_B,
> > > > +	.num_resets = 32,
> > > >  };
> > > >  
> > > >  static const struct mtk_mmsys_match_data mt8183_mmsys_match_data
> > > > =
> > > > {
> > > > @@ -114,6 +118,7 @@ static const struct mtk_mmsys_driver_data
> > > > mt8186_mmsys_driver_data = {
> > > >  	.routes = mmsys_mt8186_routing_table,
> > > >  	.num_routes = ARRAY_SIZE(mmsys_mt8186_routing_table),
> > > >  	.sw0_rst_offset = MT8186_MMSYS_SW0_RST_B,
> > > > +	.num_resets = 32,
> > > >  };
> > > 
> > > [..]
> > > > @@ -351,18 +362,6 @@ static int mtk_mmsys_probe(struct
> > > > platform_device *pdev)
> > > >  		return ret;
> > > >  	}
> > > >  
> > > > -	spin_lock_init(&mmsys->lock);
> > > > -
> > > > -	mmsys->rcdev.owner = THIS_MODULE;
> > > > -	mmsys->rcdev.nr_resets = 32;
> > > 
> > > The number of resets was previously always set to 32, and now
> > > you're
> > > instead
> > > setting it based on num_resets from each machine. The issue is,
> > > you're
> > > forgetting a bunch of them.
> > > 
> > > mt8192 didn't get a num_reset, so this commit breaks the display on
> > > mt8192 based
> > > devices. But mt8192 isn't the only one, there are other platforms
> > > missing this
> > > property. Please set num_resets to 32 in every single one of them,
> > > otherwise
> > > there will be display regressions.
> > > 
> > > Thanks,
> > > Nícolas
> > 
> > It's my mistake. I will set num_resets to 32 for every mmsys driver.
> > 
> > Thanks,
> > Nancy
> 
> After review the code, I think only the mmsys driver with the
> sw0_rst_offset setting should set num_resets to 32, otherwise it would
> set wrong addr in the mtk_mmsys_reset_update() function. Those mmsys
> without sw0_rst_offset set should not set num_resets to 32.

I don't think that's the case. num_resets and sw0_rst_offset are completely
unrelated in the code. sw0_rst_offset just gives the offset from the base
mmsys memory to the register that manages resets; it can be 0 in which case the
reset register would be right at the start of the mmsys iospace.

nr_resets, which is set by num_resets, on the other hand, seems to be used in a
single place: of_reset_simple_xlate() in drivers/reset/core.c. And the logic
there is really simple: if you pass a reset id greater than nr_resets, you will
get an error. So when you leave num_resets unset (0) for any of the platforms,
you're making all reset registrations in the DT fail.

So I'm really confident that we need num_resets = 32 on *all* platforms (except
the ones that have 64 of course, we just can't leave them empty).

Thanks,
Nícolas