linux-kernel - Re: [PATCH v7 23/25] PCI: dwc: Restore DMA-mask after MSI-data allocation

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Message-ID: <Y5w/MkA4N857+AWQ@infradead.org>
Date:   Fri, 16 Dec 2022 01:49:38 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Robin Murphy <robin.murphy@....com>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Cai Huoqing <cai.huoqing@...ux.dev>,
        Jingoo Han <jingoohan1@...il.com>, Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        caihuoqing <caihuoqing@...du.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        linux-pci@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 23/25] PCI: dwc: Restore DMA-mask after MSI-data
 allocation

On Fri, Dec 16, 2022 at 12:34:23PM +0300, Serge Semin wrote:
> What about instead of save/restore pattern I'll just change the
> dma_set_mask_and_coherent() method with the dma_set_coherent_mask()
> function call? It seems cleaner. Like this:

> Thus the platform-specific streaming DMA mask would be preserved.
> Since it's PCIe then having the streaming DMA-mask less than 32-bits
> wide is very much improbable. Moreover DW PCIe AXI-interface can be
> synthesize only with one out of two address bus widths: 32 and 64.

Where platform-specific means the dwc subdriver?  Yes, that seems
to work.  Alternatively have a flag that says which streaming mask
to set.