Re: [PATCH v2 2/2] asm-generic: Add new pci.h and use it

From: Arnd Bergmann <arnd@arndb.de>
To: Stafford Horne <shorne@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Christoph Hellwig <hch@infradead.org>,
	 LKML <linux-kernel@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
	 Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Albert Ou <aou@eecs.berkeley.edu>,
	Richard Weinberger <richard@nod.at>,
	 Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	 Bjorn Helgaas <bhelgaas@google.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	 linux-csky@vger.kernel.org,
	linux-riscv <linux-riscv@lists.infradead.org>,
	 linux-um <linux-um@lists.infradead.org>,
	linux-pci <linux-pci@vger.kernel.org>,
	 linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] asm-generic: Add new pci.h and use it
Date: Tue, 19 Jul 2022 13:55:03 +0200	[thread overview]
Message-ID: <CAK8P3a2UTND+F83k2uQ+f=o1GWV=oa5coshy8Hy+cKHUGuNzEg@mail.gmail.com> (raw)
In-Reply-To: <YtaNvpE7AA/4eV1I@antec>

On Tue, Jul 19, 2022 at 12:55 PM Stafford Horne <shorne@gmail.com> wrote:

> diff --git a/drivers/comedi/drivers/comedi_isadma.c b/drivers/comedi/drivers/comedi_isadma.c
> index 700982464c53..508421809128 100644
> --- a/drivers/comedi/drivers/comedi_isadma.c
> +++ b/drivers/comedi/drivers/comedi_isadma.c
> @@ -104,8 +104,10 @@ unsigned int comedi_isadma_poll(struct comedi_isadma *dma)
>
>         flags = claim_dma_lock();
>         clear_dma_ff(desc->chan);
> +#ifdef CONFIG_X86_32
>         if (!isa_dma_bridge_buggy)
>                 disable_dma(desc->chan);
> +#endif

There is a logic mistake here: if we are on something other than x86-32,
this always needs to call the disable_dma()/enable_dma().

Not sure how to best express this in a readable way, something like this
would work:

#ifdef CONFIG_X86_32
        if (!isa_dma_bridge_buggy)
#endif
               disable_dma(desc->chan);

or possibly at the start of this file, a

#ifndef CONFIG_X86_32
#define isa_dma_bridge_buggy 0
#endif

Or we could try to keep the generic definition in a global header
like linux/isa-dma.h.

> --- a/sound/core/isadma.c
> +++ b/sound/core/isadma.c
> @@ -73,8 +73,10 @@ unsigned int snd_dma_pointer(unsigned long dma, unsigned int size)
>
>         flags = claim_dma_lock();
>         clear_dma_ff(dma);
> +#ifdef CONFIG_X86_32
>         if (!isa_dma_bridge_buggy)
>                 disable_dma(dma);
> +#endif
>         result = get_dma_residue(dma);
>         /*

Same here.

         Arnd

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