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Date: Wed, 18 Oct 2017 10:23:36 -0700
From: Mark Greer <mgreer@animalcreek.com>
To: Huacai Chen <chenhc@lemote.com>
Cc: Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
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        linux-scsi@vger.kernel.org, Tejun Heo <tj@kernel.org>,
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        Ivan Mikhaylov <ivan@ru.ibm.com>, Tariq Toukan <tariqt@mellanox.com>,
        Andy Gross <agross@codeaurora.org>,
        "Mark A . Greer" <mgreer@animalcreek.com>,
        Robert Baldyga <r.baldyga@hackerion.com>
Subject: Re: [PATCH V8 1/5] dma-mapping: Rework dma_get_cache_alignment()
Message-ID: <20171018172336.GA29358@animalcreek.com>
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On Tue, Oct 17, 2017 at 04:05:38PM +0800, Huacai Chen wrote:
> Make dma_get_cache_alignment() to accept a 'dev' argument. As a result,
> it can return different alignments due to different devices' I/O cache
> coherency.
> 
> Currently, ARM/ARM64 and MIPS support coherent & noncoherent devices
> co-exist. This may be extended in the future, so add a new function
> pointer (i.e, get_cache_alignment) in 'struct dma_map_ops' as a generic
> solution.

Hi Huacai.

> diff --git a/drivers/tty/serial/mpsc.c b/drivers/tty/serial/mpsc.c
> index 67ffecc..c708457 100644
> --- a/drivers/tty/serial/mpsc.c
> +++ b/drivers/tty/serial/mpsc.c
> @@ -81,19 +81,19 @@
>   * Number of Tx & Rx descriptors must be powers of 2.
>   */
>  #define	MPSC_RXR_ENTRIES	32
> -#define	MPSC_RXRE_SIZE		dma_get_cache_alignment()
> +#define	MPSC_RXRE_SIZE		dma_get_cache_alignment(dma_dev)

I would much prefer that you add a parameter to the macro to avoid forcing
a non-flexible and non-obvious variable definition wherever it is used.
What I mean is something like:

#define MPSC_RXRE_SIZE(d)		dma_get_cache_alignment(d)

Similarly for all of the other macros and where they're used.

Thanks,

Mark
--