From: "Allen Hubbe" <Allen.Hubbe@dell.com>
To: "'Logan Gunthorpe'" <logang@deltatee.com>,
<linux-ntb@googlegroups.com>, <linux-kernel@vger.kernel.org>
Cc: "'Jon Mason'" <jdmason@kudzu.us>
Subject: RE: [PATCH 2/2] ntb_hw_switchtec: Check for alignment of the buffer in mw_set_trans()
Date: Mon, 11 Dec 2017 09:58:29 -0500 [thread overview]
Message-ID: <000201d37290$81605eb0$84211c10$@dell.com> (raw)
In-Reply-To: <20171209000217.18366-2-logang@deltatee.com>
From: Logan Gunthorpe
> With Switchtec hardware, the buffer used for a memory window must be
> aligned to its size (the hardware only replaces the lower bits). In
> certain circumstances dma_alloc_coherent() will not provide a buffer
> that adheres to this requirement like when using the CMA and
> CONFIG_CMA_ALIGNMENT is set lower than the buffer size.
>
> When we get an unaligned buffer mw_set_trans() should return an error.
> We also log an error so we know the cause of the problem.
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Cc: Jon Mason <jdmason@kudzu.us>
> ---
> drivers/ntb/hw/mscc/ntb_hw_switchtec.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/ntb/hw/mscc/ntb_hw_switchtec.c b/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
> index 709f37fbe232..984b83bc7dd3 100644
> --- a/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
> +++ b/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
> @@ -315,6 +315,19 @@ static int switchtec_ntb_mw_set_trans(struct ntb_dev *ntb, int pidx, int widx,
> if (xlate_pos < 12)
> return -EINVAL;
>
> + if (addr & ((1 << xlate_pos) - 1)) {
!IS_ALIGNED(addr, BIT_ULL(xlate_pos))
> + /*
> + * In certain circumstances we can get a buffer that is
> + * not aligned to its size. (Most of the time
> + * dma_alloc_coherent ensures this). This can happen when
> + * using large buffers allocated by the CMA
> + * (see CMA_CONFIG_ALIGNMENT)
> + */
> + dev_err(&sndev->stdev->dev,
> + "ERROR: Memory window address is not aligned to it's size!\n");
This would be the only ntb hw driver that prints an error in this situation. The ntb_mw_get_align() should provide enough information to client drivers to determine the alignment requirements before calling ntb_mw_set_trans(). IMO no need to print here, but let's see what others say.
> + return -EINVAL;
> + }
> +
> rc = switchtec_ntb_part_op(sndev, ctl, NTB_CTRL_PART_OP_LOCK,
> NTB_CTRL_PART_STATUS_LOCKED);
> if (rc)
> --
> 2.11.0
next prev parent reply other threads:[~2017-12-11 14:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-09 0:02 [PATCH 1/2] ntb_transport: Fix bug with max_mw_size parameter Logan Gunthorpe
2017-12-09 0:02 ` [PATCH 2/2] ntb_hw_switchtec: Check for alignment of the buffer in mw_set_trans() Logan Gunthorpe
2017-12-11 14:58 ` Allen Hubbe [this message]
2017-12-11 17:14 ` Logan Gunthorpe
2017-12-11 19:17 ` Allen Hubbe
2017-12-11 19:28 ` Logan Gunthorpe
2017-12-11 20:06 ` Allen Hubbe
2017-12-11 20:38 ` Logan Gunthorpe
2017-12-11 14:55 ` [PATCH 1/2] ntb_transport: Fix bug with max_mw_size parameter Allen Hubbe
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