linux-kernel - Re: [PATCH 8/8] habanalabs: enable 64-bit DMA mask in POWER9

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Message-ID: <20190611151247.GA3110@infradead.org>
Date:   Tue, 11 Jun 2019 08:12:47 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Oded Gabbay <oded.gabbay@...il.com>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org
Subject: Re: [PATCH 8/8] habanalabs: enable 64-bit DMA mask in POWER9

On Tue, Jun 11, 2019 at 08:50:45AM +0300, Oded Gabbay wrote:
> 2. The pci_set_dma_mask() is a generic Linux kernel call, so the driver
>    can't tell why it got an error when it tried to set the DMA mask to 48
>    bits. And upon such failure, the driver must fall-back to set the mask
>    to 32 bits.

In the current kernel pci_set_dma_mask only fails if the DMA mask is
to small to be supportable at all.  So you very obviously did not
actually test this against mainline.