linux-kernel - Re: [PATCH] [v2] dmaengine: dw-edma: reduce stack usage after debugfs rework

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Date:   Sun, 12 Feb 2023 22:23:47 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Vinod Koul <vkoul@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Arnd Bergmann <arnd@...nel.org>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Arnd Bergmann <arnd@...db.de>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Frank Li <Frank.Li@....com>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] dmaengine: dw-edma: reduce stack usage after
 debugfs rework

On Fri, Feb 10, 2023 at 05:29:40PM -0600, Bjorn Helgaas wrote:
> On Fri, Feb 10, 2023 at 03:35:25PM +0300, Serge Semin wrote:
> > 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@...db.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@...db.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?
> 

> Yes, I squashed this into the original patch and tweaked the
> whitespace per Manivannan's comment.

Great! Thanks.

> 
> Note that we've moved to a shared PCI git tree, so the helgaas/pci.git
> tree is obsolete and will bit rot until we remove it completely.
> 
> The new one is:
> 
>   https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/

Good to know. Thanks again.

-Serge(y)

> 
> Bjorn