From: Shanker Donthineni <shankerd@codeaurora•org>
To: Timur Tabi <timur@codeaurora•org>, Rob Herring <robh@kernel•org>
Cc: netdev@vger•kernel.org, devicetree@vger•kernel.org,
linux-arm-msm@vger•kernel.org, sdharia@codeaurora•org,
vikrams@codeaurora•org, cov@codeaurora•org,
gavidov@codeaurora•org, andrew@lunn•ch,
bjorn.andersson@linaro•org, mlangsdo@redhat•com, jcm@redhat•com,
agross@codeaurora•org, davem@davemloft•net, f.fainelli@gmail•com
Subject: Re: [PATCH] [v5] net: emac: emac gigabit ethernet controller driver
Date: Mon, 20 Jun 2016 13:04:25 -0500 [thread overview]
Message-ID: <57683029.1090601@codeaurora.org> (raw)
In-Reply-To: <57682AC3.4040003@codeaurora.org>
Timur,
I think, the device driver is responsible for setting the right DMA_MASK
based on the underlying hardware capability if your driver wants to
support 64bit DMA.
Example code in drivers/usb/host/xhci.c:
/* Set dma_mask and coherent_dma_mask to 64-bits,
* if xHC supports 64-bit addressing */
if (HCC_64BIT_ADDR(xhci->hcc_params) &&
!dma_set_mask(dev, DMA_BIT_MASK(64))) {
xhci_dbg(xhci, "Enabling 64-bit DMA addresses.\n");
dma_set_coherent_mask(dev, DMA_BIT_MASK(64));
} else {
/*
* This is to avoid error in cases where a 32-bit USB
* controller is used on a 64-bit capable system.
*/
retval = dma_set_mask(dev, DMA_BIT_MASK(32));
On 06/20/2016 12:41 PM, Timur Tabi wrote:
> Rob Herring wrote:
>>> >+ dma-ranges = <0 0 0xffffffff>;
>> I believe dma-ranges is supposed to be in the bus (parent) node.
>
> Maybe I'm just going to be perpetually confused by dma-ranges, but how
> can I specify that the emac has a different DMA range from another SOC
> device, if dma-ranges is in the parent node?
>
> The EMAC itself is capable of 64-bit DMA internally (I should have
> included a dma_set_mask call with DMA_BIT_MASK(64) in the driver).
> However, the platform typically limits this range. On FSM9900 and
> QDF2432, it's 32 bits. On the next server chip, it'll be the full 64
> bits. I need some way to handle that.
>
--
Shanker Donthineni
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2016-06-20 18:04 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-14 22:22 [PATCH] [v5] net: emac: emac gigabit ethernet controller driver Timur Tabi
2016-06-16 4:41 ` David Miller
2016-06-16 5:05 ` Timur Tabi
2016-06-19 14:17 ` Rob Herring
2016-06-20 17:41 ` Timur Tabi
2016-06-20 18:04 ` Shanker Donthineni [this message]
2016-06-20 18:15 ` Timur Tabi
2016-06-20 18:49 ` Timur Tabi
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