linux-kernel - Re: [PATCH v5 11/12] ARM64: add dma remap for BrcmSTB PCIe

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Message-ID: <20180919144119.GB29096@lst.de>
Date:   Wed, 19 Sep 2018 16:41:19 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jim Quinlan <jim2101024@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Brian Norris <computersforpeace@...il.com>,
        Gregory Fong <gregory.0xf0@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v5 11/12] ARM64: add dma remap for BrcmSTB PCIe

On Wed, Sep 19, 2018 at 10:32:06AM -0400, Jim Quinlan wrote:
> +#if defined(CONFIG_ARM64)

Please use plain #ifdef where possible.

> +dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
> +{
> +	return brcm_phys_to_dma(dev, paddr);
> +}
> +
> +phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> +{
> +	return brcm_dma_to_phys(dev, dev_addr);
> +}
> +#endif

How is this going to work for a kernel with BrcmSTB built in, but running
on a more standard arm64 SOC?

I suspect we really just want a set of ranges hanging off struct device
(conditional on a config option).  Each SoC can then fill it at boot
time, and if it is non-NULL the DMA code will use it instead of
calling __phys_to_dma and __dma_to_phys.  In fact the single range
version could probably just replace the existing dma_pfn_offset
field.