linux-kernel - Re: [PATCH 7/9] ethernet: stmicro: Simplify PCI devres usage

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Message-ID: <ZsRx6OyqHPL0ws0e@smile.fi.intel.com>
Date: Tue, 20 Aug 2024 13:37:28 +0300
From: Andy Shevchenko <andy@...nel.org>
To: Philipp Stanner <pstanner@...hat.com>
Cc: onathan Corbet <corbet@....net>, Jens Axboe <axboe@...nel.dk>,
	Wu Hao <hao.wu@...el.com>, Tom Rix <trix@...hat.com>,
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Subject: Re: [PATCH 7/9] ethernet: stmicro: Simplify PCI devres usage

On Tue, Aug 20, 2024 at 09:52:40AM +0200, Philipp Stanner wrote:
> On Mon, 2024-08-19 at 21:28 +0300, Andy Shevchenko wrote:
> > On Mon, Aug 19, 2024 at 06:51:47PM +0200, Philipp Stanner wrote:

...

> > loongson_dwmac_probe()
> > 
> > > +	memset(&res, 0, sizeof(res));
> > > +	res.addr = pcim_iomap_region(pdev, 0, pci_name(pdev));
> > > +	if (IS_ERR(res.addr)) {
> > > +		ret = PTR_ERR(res.addr);
> > > +		goto err_disable_device;
> > 
> > It seems your series reveals issues in the error paths of .probe():s
> > in many drivers...
> > 
> > If we use pcim variant to enable device, why do we need to explicitly
> > disable it?
> 
> No.

Can you elaborate? No issues being revealed, or no need to disable it
explicitly, or...?

> > >  	}

...

> > loongson_dwmac_remove()
> > 
> > >  	pci_disable_msi(pdev);
> > >  	pci_disable_device(pdev);
> > 
> > Not sure why we need these either...
> 
> It's complicated.
> 
> The code uses pciM_enable_device(), but here in remove
> pci_disable_device().
> 
> pcim_enable_device() sets up a disable callback which only calls
> pci_disable_device() if pcim_pin_device() has not been called.
> 
> This code doesn't seem to call pcim_pin_device(), so I think
> pci_disable_device() could be removed.
> 
> 
> I definitely would not feel confident touching pci_disable_msi(),
> though. The AFAIK biggest problem remaining in PCI devres is that the
> MSI code base implicitly calls into devres, see here [1]

But isn't it a busyness of PCI core to call pci_disable_msi() at the right
moment? Okay, I admit that there might be devices that require a special
workflow WRT MSI, is this the case here?

> [1] https://lore.kernel.org/all/ee44ea7ac760e73edad3f20b30b4d2fff66c1a85.camel@redhat.com/

-- 
With Best Regards,
Andy Shevchenko