From: acourbot@nvidia•com (Alexandre Courbot)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: mach-imx: sdhci-esdhc-imx: initialize DMA mask
Date: Tue, 12 Apr 2016 21:25:04 +0900 [thread overview]
Message-ID: <570CE920.4040204@nvidia.com> (raw)
In-Reply-To: <570CC6F2.4090301@intel.com>
On 04/12/2016 06:59 PM, Adrian Hunter wrote:
> On 12/04/16 11:40, Russell King - ARM Linux wrote:
>> On Tue, Apr 12, 2016 at 09:05:34AM +0300, Adrian Hunter wrote:
>>> On 11/04/16 19:13, Alexander Kurz wrote:
>>>> Hi Adrian,
>>>> On Mon, 11 Apr 2016, Adrian Hunter wrote:
>>>>
>>>>> On 11/04/16 11:35, Uwe Kleine-K?nig wrote:
>>>>>> Hello,
>>>>>>
>>>>>> I added the people involved in 7b91369b4655 to Cc.
>>>>>>
>>>>>> On Mon, Apr 11, 2016 at 10:20:46AM +0200, Alexander Kurz wrote:
>>>>>>> With commit 7b91369b DMA access got disabled for device drivers with zero
>>>>>
>>>>> Is that because dma_set_mask_and_coherent() fails?
>>>> right, dma_set_mask_and_coherent() fails, thats the only reason for
>>>> this patch. This popped up on a Kindle3 (IMX35 with eMMC based root fs).
>>>
>>> Arnd, Alexandre : Why should dma_set_mask_and_coherent() fail in this case
>>> when DMA apparently doesn't need a dma_mask anyway?
>>
>> What do you mean "doesn't need a dma_mask" ? DMA _always_ requires a
>> DMA mask. The DMA mask defines how many address bits are capable of
>> being used on the bus.
>>
>> If there's no DMA mask, then there's no usable address bits, and so
>> the device is not DMA capable. Hence, dma_set_mask_and_coherent()
>> will fail because its not possible to negotiate a non-zero number of
>> address bits.
>>
>
> The point is, now we valid dma_set_mask_and_coherent(), DMA will stop
> working for any other SDHCI device that hasn't allocated dev.dma_mask. Is
> that OK?
Clearly these devices need to be fixed. If we want to give them a grace
period, we could also (temporarily) not propagate the return value of
dma_set_mask_and_coherent() and limit ourselves to emitting a big
warning about the inconsistency of having SDHCI_USE_SDMA/SDHCI_USE_ADMA
in the host flags while not setting a dma mask.
But in the past, how prompt have people been to react to such warnings
vs. their device not working as expected?
next prev parent reply other threads:[~2016-04-12 12:25 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-11 8:20 [PATCH] ARM: mach-imx: sdhci-esdhc-imx: initialize DMA mask Alexander Kurz
2016-04-11 8:35 ` Uwe Kleine-König
2016-04-11 10:10 ` Adrian Hunter
2016-04-11 16:13 ` Alexander Kurz
2016-04-12 6:05 ` Adrian Hunter
2016-04-12 8:40 ` Russell King - ARM Linux
2016-04-12 9:59 ` Adrian Hunter
2016-04-12 12:25 ` Alexandre Courbot [this message]
2016-04-12 15:31 ` Russell King - ARM Linux
2016-04-13 2:02 ` Alexandre Courbot
2016-04-13 8:07 ` Adrian Hunter
2016-04-16 21:48 ` Arnd Bergmann
2016-04-18 6:58 ` Adrian Hunter
2016-04-18 14:33 ` Arnd Bergmann
[not found] ` <57232233.1030702@intel.com>
2016-04-29 8:59 ` Potential issue with SDHCI DMA Adrian Hunter
2016-04-29 9:19 ` Jisheng Zhang
2016-04-12 15:29 ` [PATCH] ARM: mach-imx: sdhci-esdhc-imx: initialize DMA mask Russell King - ARM Linux
2016-04-11 12:46 ` Sergei Shtylyov
2016-04-13 1:38 ` Shawn Guo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=570CE920.4040204@nvidia.com \
--to=acourbot@nvidia$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox