Date:   Fri, 10 Feb 2023 15:35:25 +0300
From:   Serge Semin <fancer.lancer@gmail.com>
To:     Vinod Koul <vkoul@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>
Cc:     Arnd Bergmann <arnd@kernel.org>,
        Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
        Serge Semin <Sergey.Semin@baikalelectronics.ru>,
        Arnd Bergmann <arnd@arndb.de>,
        Manivannan Sadhasivam <mani@kernel.org>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        Frank Li <Frank.Li@nxp.com>, dmaengine@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [v2] dmaengine: dw-edma: reduce stack usage after
 debugfs rework
Message-ID: <20230210123525.cphmtcf7pmfj67os@mobilestation.baikal.int>
References: <20230130185101.2883245-1-arnd@kernel.org>
 <Y+YFzDm4XOnzZTpM@matsya>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Y+YFzDm4XOnzZTpM@matsya>
Precedence: bulk

Hello Vinod

On Fri, Feb 10, 2023 at 02:22:28PM +0530, Vinod Koul wrote:
> On 30-01-23, 19:50, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> > 
> > After the dw_edma_debugfs_entry arrays are no longer compile-time
> > constant, they take up space on the stack, which exceeds the warning
> > limit after inlining:
> > 
> > drivers/dma/dw-edma/dw-edma-v0-debugfs.c:280:6: error: stack frame size (1784) exceeds limit (1400) in 'dw_edma_v0_debugfs_on' [-Werror,-Wframe-larger-than]
> > void dw_edma_v0_debugfs_on(struct dw_edma *dw)
> > 
> > Work around this by preventing dw_edma_debugfs_regs_{wr,rd} from both
> > being inlined together, which cuts the stack frame size in half and
> > makes it fit below the warning limit.
> > 
> > Fixes: 5c0373eafd83 ("dmaengine: dw-edma: Move eDMA data pointer to debugfs node descriptor")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> > v2: rebase on top of dmaengine tree
> 
> I dont have 5c0373eafd83 in my tree, I guess that went thru PCI tree, so
> I am going to defer this after merge window

It's in the @Bjorn tree now
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=pci/ctrl/dwc&id=5c0373eafd8334343da22338d8588ed61e8daba0

If you are ok with the fix then @Bjorn could take the patch in to his
repo. Right, @Bjorn?

-Serge(y)

> 
> > ---
> >  drivers/dma/dw-edma/dw-edma-v0-debugfs.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> > index 42380bf64a70..6542060bd01a 100644
> > --- a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> > +++ b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> > @@ -136,7 +136,8 @@ static void dw_edma_debugfs_regs_ch(struct dw_edma *dw, enum dw_edma_dir dir,
> >  	dw_edma_debugfs_create_x32(dw, debugfs_regs, nr_entries, dent);
> >  }
> >  
> > -static void dw_edma_debugfs_regs_wr(struct dw_edma *dw, struct dentry *dent)
> > +static noinline_for_stack void
> > +dw_edma_debugfs_regs_wr(struct dw_edma *dw, struct dentry *dent)
> >  {
> >  	const struct dw_edma_debugfs_entry debugfs_regs[] = {
> >  		/* eDMA global registers */
> > @@ -197,7 +198,8 @@ static void dw_edma_debugfs_regs_wr(struct dw_edma *dw, struct dentry *dent)
> >  	}
> >  }
> >  
> > -static void dw_edma_debugfs_regs_rd(struct dw_edma *dw, struct dentry *dent)
> > +static noinline_for_stack void
> > +dw_edma_debugfs_regs_rd(struct dw_edma *dw, struct dentry *dent)
> >  {
> >  	const struct dw_edma_debugfs_entry debugfs_regs[] = {
> >  		/* eDMA global registers */
> > -- 
> > 2.39.0
> 
> -- 
> ~Vinod