Re: question about block layer and dma alignment issue.

Re: question about block layer and dma alignment issue.

[Oleksij Rempel]

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Am 04.10.2014 um 19:00 schrieb Jens Axboe:
> On 2014-10-04 00:59, Oleksij Rempel wrote:
>> Hello Jens,
>>
>> i hope it is OK to ask you directly, i didn't found better way to do
>> this.
>> I'm writing MMC driver based on reverse engineering for au6601 mmc
>> controller. This driver uses MMC API, and last one trying to use BLK API
>> as directly as possible. So far so gut, but i have a problem by using SG
>> requests with DMA without conversation. This controller accepts only
>> addresses with this mask 0xffff.f000 - also page aligned.
>> Till now i tried different QUEUE_FLAG_ flags and blk_queue settings, but
>> i never had absolute aligned quarantine.
>> Please tell me if i do some thing wrong or go in the wrong direction.
> 
> Unless you can accept a 4kb hardware block size (and I'm assuming you
> cannot, since you need to support 512b file systems?), then you'd have
> to bounce the requests that don't align properly. You can fix some of
> them by setting blk_queue_dma_alignment(q, 4095).

I needed to include MMC list with Ulf Hansson at the beginning, so here
we are.

Hi Ulf,

here is the list of drivers which do care about dma alignment . Some of
them use bounce_buffer, some will use PIO instead of DMA, for not
aligned requests:

dw_mmc.c: dw_mci_pre_dma_transfer
wbsd.c
usdhi6rol0.c
tmio_mmc_dma.c
sunxi-mmc.c
sdhci.c
pxamci.c
mvsdio.c
au6601.c(not upstream jet)

The problem of all this driver is that each of them use own solution. I
think this code can be moved to some common place. For example, it can
be done in drivers/mmc/card/queue.c and enabled by
mmc_host_dma_alignment variable. Or provide a mmc_sg_align() function,
which should be called explicatively by driver.

Which option is preferable?

-- 
Regards,
Oleksij


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Re: question about block layer and dma alignment issue.

[Jens Axboe]

On 10/07/2014 03:37 AM, Oleksij Rempel wrote:
> Am 04.10.2014 um 19:00 schrieb Jens Axboe:
>> On 2014-10-04 00:59, Oleksij Rempel wrote:
>>> Hello Jens,
>>>
>>> i hope it is OK to ask you directly, i didn't found better way to do
>>> this.
>>> I'm writing MMC driver based on reverse engineering for au6601 mmc
>>> controller. This driver uses MMC API, and last one trying to use BLK API
>>> as directly as possible. So far so gut, but i have a problem by using SG
>>> requests with DMA without conversation. This controller accepts only
>>> addresses with this mask 0xffff.f000 - also page aligned.
>>> Till now i tried different QUEUE_FLAG_ flags and blk_queue settings, but
>>> i never had absolute aligned quarantine.
>>> Please tell me if i do some thing wrong or go in the wrong direction.
>>
>> Unless you can accept a 4kb hardware block size (and I'm assuming you
>> cannot, since you need to support 512b file systems?), then you'd have
>> to bounce the requests that don't align properly. You can fix some of
>> them by setting blk_queue_dma_alignment(q, 4095).
> 
> I needed to include MMC list with Ulf Hansson at the beginning, so here
> we are.
> 
> Hi Ulf,
> 
> here is the list of drivers which do care about dma alignment . Some of
> them use bounce_buffer, some will use PIO instead of DMA, for not
> aligned requests:
> 
> dw_mmc.c: dw_mci_pre_dma_transfer
> wbsd.c
> usdhi6rol0.c
> tmio_mmc_dma.c
> sunxi-mmc.c
> sdhci.c
> pxamci.c
> mvsdio.c
> au6601.c(not upstream jet)
> 
> The problem of all this driver is that each of them use own solution. I
> think this code can be moved to some common place. For example, it can
> be done in drivers/mmc/card/queue.c and enabled by
> mmc_host_dma_alignment variable. Or provide a mmc_sg_align() function,
> which should be called explicatively by driver.
> 
> Which option is preferable?

I would roll a block version that they all can use, you can look at
block/bounce.c for inspiration. That file deals with bouncing higher
pages to lower memory, so it's not exactly what you want. But the metod
of allocating a new bio that meets criteria and copying data over, that
is the same that you need.

-- 
Jens Axboe

Re: question about block layer and dma alignment issue.

[Oleksij Rempel]

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Am 07.10.2014 um 17:25 schrieb Jens Axboe:
> On 10/07/2014 03:37 AM, Oleksij Rempel wrote:
>> Am 04.10.2014 um 19:00 schrieb Jens Axboe:
>>> On 2014-10-04 00:59, Oleksij Rempel wrote:
>>>> Hello Jens,
>>>>
>>>> i hope it is OK to ask you directly, i didn't found better way to do
>>>> this.
>>>> I'm writing MMC driver based on reverse engineering for au6601 mmc
>>>> controller. This driver uses MMC API, and last one trying to use BLK API
>>>> as directly as possible. So far so gut, but i have a problem by using SG
>>>> requests with DMA without conversation. This controller accepts only
>>>> addresses with this mask 0xffff.f000 - also page aligned.
>>>> Till now i tried different QUEUE_FLAG_ flags and blk_queue settings, but
>>>> i never had absolute aligned quarantine.
>>>> Please tell me if i do some thing wrong or go in the wrong direction.
>>>
>>> Unless you can accept a 4kb hardware block size (and I'm assuming you
>>> cannot, since you need to support 512b file systems?), then you'd have
>>> to bounce the requests that don't align properly. You can fix some of
>>> them by setting blk_queue_dma_alignment(q, 4095).
>>
>> I needed to include MMC list with Ulf Hansson at the beginning, so here
>> we are.
>>
>> Hi Ulf,
>>
>> here is the list of drivers which do care about dma alignment . Some of
>> them use bounce_buffer, some will use PIO instead of DMA, for not
>> aligned requests:
>>
>> dw_mmc.c: dw_mci_pre_dma_transfer
>> wbsd.c
>> usdhi6rol0.c
>> tmio_mmc_dma.c
>> sunxi-mmc.c
>> sdhci.c
>> pxamci.c
>> mvsdio.c
>> au6601.c(not upstream jet)
>>
>> The problem of all this driver is that each of them use own solution. I
>> think this code can be moved to some common place. For example, it can
>> be done in drivers/mmc/card/queue.c and enabled by
>> mmc_host_dma_alignment variable. Or provide a mmc_sg_align() function,
>> which should be called explicatively by driver.
>>
>> Which option is preferable?
> 
> I would roll a block version that they all can use, you can look at
> block/bounce.c for inspiration. That file deals with bouncing higher
> pages to lower memory, so it's not exactly what you want. But the metod
> of allocating a new bio that meets criteria and copying data over, that
> is the same that you need.

Ok,

i will need to setup testing board for this kind of work. It will take
some time.

-- 
Regards,
Oleksij


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Re: question about block layer and dma alignment issue.

[Adrian Hunter]

On 8/10/2014 9:50 a.m., Oleksij Rempel wrote:
> Am 07.10.2014 um 17:25 schrieb Jens Axboe:
>> On 10/07/2014 03:37 AM, Oleksij Rempel wrote:
>>> Am 04.10.2014 um 19:00 schrieb Jens Axboe:
>>>> On 2014-10-04 00:59, Oleksij Rempel wrote:
>>>>> Hello Jens,
>>>>>
>>>>> i hope it is OK to ask you directly, i didn't found better way to do
>>>>> this.
>>>>> I'm writing MMC driver based on reverse engineering for au6601 mmc
>>>>> controller. This driver uses MMC API, and last one trying to use BLK API
>>>>> as directly as possible. So far so gut, but i have a problem by using SG
>>>>> requests with DMA without conversation. This controller accepts only
>>>>> addresses with this mask 0xffff.f000 - also page aligned.
>>>>> Till now i tried different QUEUE_FLAG_ flags and blk_queue settings, but
>>>>> i never had absolute aligned quarantine.
>>>>> Please tell me if i do some thing wrong or go in the wrong direction.
>>>> Unless you can accept a 4kb hardware block size (and I'm assuming you
>>>> cannot, since you need to support 512b file systems?), then you'd have
>>>> to bounce the requests that don't align properly. You can fix some of
>>>> them by setting blk_queue_dma_alignment(q, 4095).
>>> I needed to include MMC list with Ulf Hansson at the beginning, so here
>>> we are.
>>>
>>> Hi Ulf,
>>>
>>> here is the list of drivers which do care about dma alignment . Some of
>>> them use bounce_buffer, some will use PIO instead of DMA, for not
>>> aligned requests:
>>>
>>> dw_mmc.c: dw_mci_pre_dma_transfer
>>> wbsd.c
>>> usdhi6rol0.c
>>> tmio_mmc_dma.c
>>> sunxi-mmc.c
>>> sdhci.c
>>> pxamci.c
>>> mvsdio.c
>>> au6601.c(not upstream jet)
>>>
>>> The problem of all this driver is that each of them use own solution. I
>>> think this code can be moved to some common place. For example, it can
>>> be done in drivers/mmc/card/queue.c and enabled by
>>> mmc_host_dma_alignment variable. Or provide a mmc_sg_align() function,
>>> which should be called explicatively by driver.
>>>
>>> Which option is preferable?
>> I would roll a block version that they all can use, you can look at
>> block/bounce.c for inspiration. That file deals with bouncing higher
>> pages to lower memory, so it's not exactly what you want. But the metod
>> of allocating a new bio that meets criteria and copying data over, that
>> is the same that you need.

Not all cards are block devices e.g. SDIO wifi.  And there is also mmc_test.

> Ok,
>
> i will need to setup testing board for this kind of work. It will take
> some time.
>