Re: [EXT] about DMA API updates proposal


Kumar Gala
 

I can present the two options that Hake and I have discussed in this thread to see if there’s any feedback on which direction to take for the new API that is being suggested.

(Happy to do this so Hake doesn’t have to be awake at a crazy hour for him).

- k

On Mar 9, 2021, at 6:17 AM, Cufi, Carles <Carles.Cufi@nordicsemi.no> wrote:

Hi Hake,

Is this something you want to discuss at the API meeting today? It's at 18h CET.

Thanks,

Carles

-----Original Message-----
From: devel@lists.zephyrproject.org <devel@lists.zephyrproject.org> On
Behalf Of Hake Huang via lists.zephyrproject.org
Sent: 09 March 2021 12:56
To: Kumar Gala <kumar.gala@linaro.org>
Cc: devel@lists.zephyrproject.org; Maureen Helm <maureen.helm@nxp.com>;
Erwan Gouriou <erwan.gouriou@linaro.org>
Subject: Re: [Zephyr-devel] [EXT] about DMA API updates proposal

Hi Gala,

I create a new PR
https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.c
om%2Fzephyrproject-
rtos%2Fzephyr%2Fpull%2F33174&amp;data=04%7C01%7Ccarles.cufi%40nordicsemi.n
o%7C2f7fefddf3df4385a77008d8e2f26416%7C28e5afa2bf6f419a8cf6b31c6e9e5e8d%7C
0%7C0%7C637508879620655760%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJ
QIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=xJlwTcev57aEZ
bDlldIUODWfUpNLzH7SbIUnbTvqMNw%3D&amp;reserved=0 dedicated for the two new
APIS, please check. Thanks in advance.

Regards,
Hake

-----Original Message-----
From: Hake Huang
Sent: 2021年3月5日 11:56
To: Kumar Gala <kumar.gala@linaro.org>
Cc: devel@lists.zephyrproject.org; Maureen Helm <maureen.helm@nxp.com>;
Erwan Gouriou <erwan.gouriou@linaro.org>
Subject: RE: [Zephyr-devel] [EXT] about DMA API updates proposal

Hi Gala,

I try to find some reference from Linux code, and below is my finding.

https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.hui
hoo.com%2Fdoxygen%2Flinux%2Fkernel%2F3.7%2Fdmatest_8c_source.html&amp;data
=04%7C01%7Ccarles.cufi%40nordicsemi.no%7C2f7fefddf3df4385a77008d8e2f26416%
7C28e5afa2bf6f419a8cf6b31c6e9e5e8d%7C0%7C0%7C637508879620665756%7CUnknown%
7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6
Mn0%3D%7C3000&amp;sdata=Sq5QarVur4smW1zz1sWY6nRBMwca2lCnzmMVW9Z9kNI%3D&amp
;reserved=0
614 static bool filter(struct dma_chan *chan, void *param)
615 {
616 if (!dmatest_match_channel(chan) || !dmatest_match_device(chan-
device))
617 return false;
618 else
619 return true;
620 }
621
622 static int __init dmatest_init(void)
623 {
624 dma_cap_mask_t mask;
625 struct dma_chan *chan;
626 int err = 0;
627
628 dma_cap_zero(mask);
629 dma_cap_set(DMA_MEMCPY, mask);
630 for (;;) {
631 chan = dma_request_channel(mask, filter, NULL);
632 if (chan) {
633 err = dmatest_add_channel(chan);
634 if (err) {
635 dma_release_channel(chan);
636 break; /* add_channel failed, punt */
637 }
638 } else
639 break; /* no more channels available */
640 if (max_channels && nr_channels >= max_channels)
641 break; /* we have all we need */
642 }
643
644 return err;
645 }

In Linux the dma api use a filter function point as its parameter, so the
zephyr request API can be

static int dma_edma_request_channel(const struct device *dev,
channel_filter_func filter, void *
filter_param) {
int i = 0;
int channel = -EINVAL;

k_mutex_lock(&DEV_DATA(dev)->dma_mutex, K_FOREVER);

for (i = 0; i < DEV_CFG(dev)->dma_channels; i++) {
if (!atomic_test_and_set_bit(DEV_DATA(dev)->dma_channels, i))
{
channel = i;
if (fn && !fn(filter_param)) {
continue;
}
break;
}
}
k_mutex_unlock(&DEV_DATA(dev)->dma_mutex);

return channel;
}

And each SOC vender response to provide the filter function, if no filter
then just give NULL.


How about this solution?

Regards,
Hake

-----Original Message-----
From: Kumar Gala <kumar.gala@linaro.org>
Sent: 2021年3月4日 23:00
To: Hake Huang <hake.huang@nxp.com>
Cc: devel@lists.zephyrproject.org; Maureen Helm <maureen.helm@nxp.com>;
Erwan Gouriou <erwan.gouriou@linaro.org>
Subject: Re: [Zephyr-devel] [EXT] about DMA API updates proposal

Caution: EXT Email

1. I think we handle that on a case by case basis and wait and see how it
develops over time. If we keep these APIs vendor specific for now we can
refactor or introduce a general API for ‘filter’ when we see the pattern.

2. The ‘if’ has to exist somewhere. The ‘if’ is either in the API or the
caller.

The concern I have is we don’t know what kinda of ‘filters’ we need today
beyond the ‘periodic’ one which is specific to NXP hardware.

- k

On Mar 3, 2021, at 9:27 PM, Hake Huang <hake.huang@nxp.com> wrote:

Hi Gala,

According to the usage of these two APIs, I have two concerns

1. What if there are other special DMA attribute than periodic? We will
have to add more APIs?
2. in the peripheral driver, the DMA request can be periodic or not
periodic, then we have to use if else instead of a simple call with
filter.

Regards,
Hake
-----Original Message-----
From: Kumar Gala <kumar.gala@linaro.org>
Sent: 2021年3月3日 22:49
To: Kumar Gala <kumar.gala@linaro.org>
Cc: Hake Huang <hake.huang@nxp.com>; devel@lists.zephyrproject.org;
Maureen Helm <maureen.helm@nxp.com>; Erwan Gouriou
<erwan.gouriou@linaro.org>
Subject: Re: [Zephyr-devel] [EXT] about DMA API updates proposal

Caution: EXT Email

Hake,

So I was thinking about the following idea:

Having 2 general purpose APIs:

dma_request_channel(const struct device *dev)
dma_release_channel(const struct device *dev)

Than 2 eDMA specific APIs:

mcux_edma_request_periodic_channel(const struct device *dev)
mcux_edma_release_periodic_channel(const struct device *dev)

- k

On Mar 2, 2021, at 9:28 PM, Kumar Gala via lists.zephyrproject.org
<kumar.gala=linaro.org@lists.zephyrproject.org> wrote:

Hake,

The ‘filter’ feature I’m still trying to figure out how we handle. I’m
curious if other vendors have channels that have specific features like
‘periodic’ that only are supported on specific channels or not.

Hopefully, Erwan might be able to know for STM32.

- k

On Mar 2, 2021, at 9:06 PM, Hake Huang <hake.huang@nxp.com> wrote:

Hi Gala,

I will create a separated PR for DMA new API only.

and one question for below:
"use some of the generic devicetree properties in
"dts/bindings/dma/dma-controller.yaml”. The number space allocation code
seems pretty generic"

Do you mean, instead of just add API call but move below implement to
common code?

static int dma_mcux_edma_request_channel(const struct device *dev,
enum dma_channel_filter filter)
{
int i = 0;
int channel = -EINVAL;

k_mutex_lock(&DEV_DATA(dev)->dma_mutex, K_FOREVER);

for (i = 0; i < DEV_CFG(dev)->dma_channels; i++) {
/* channel 0-3 is Period trigger enabled */
if (filter == DMA_CHANNEL_PERIODIC && i > 3) {
break;
}
if (!atomic_test_and_set_bit(DEV_DATA(dev)->dma_channels,
i)) {
channel = i;
break;
}
}

k_mutex_unlock(&DEV_DATA(dev)->dma_mutex);

return channel;
}

If so the filter is hard to aligned, as different SOC has different
filter setting.

Regards,
Hake

-----Original Message-----
From: Kumar Gala <kumar.gala@linaro.org>
Sent: 2021年3月3日 1:43
To: Hake Huang <hake.huang@nxp.com>
Cc: devel@lists.zephyrproject.org; Maureen Helm
<maureen.helm@nxp.com>
Subject: [EXT] Re: about DMA API updates proposal

Caution: EXT Email

On Feb 26, 2021, at 5:46 AM, Hake Huang <hake.huang@nxp.com> wrote:

Hi All,

I am working on enable NXP EDMA drivers to Zephyr DMA framework, and
I have two DMA API changes need to discussion.
1.
https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.c
om%2Fzephyrproject-
rtos%2Fzephyr%2Fpull%2F28895&amp;data=04%7C01%7Ccarles.cufi%40nordicsemi.n
o%7C2f7fefddf3df4385a77008d8e2f26416%7C28e5afa2bf6f419a8cf6b31c6e9e5e8d%7C
0%7C0%7C637508879620665756%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJ
QIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=HpXjVqCHdnoRg
IbGlttgT2pLgUWUr%2Fx3oaLgsR479F4%3D&amp;reserved=0
in this PR, I add chain_link by using the dest_chaining_en(Major) and
source_chaining_en(minor).
2.
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fg
i
th
ub.com%2Fzephyrproject-rtos%2Fzephyr%2Fpull%2F27737&amp;data=04%7C0
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Chake.huang%40nxp.com%7C3753d08aba3a4799ddb008d8dda294b0%7C686ea1d3
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GZ
sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn
0
%3
D%7C1000&amp;sdata=3QEP18IvoC9MS3C9o274Z0eMIdbIWTzaoZp18la0OzQ%3D&a
m
p;
reserved=0 in this PR,
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fg
i
th
ub.com%2Fzephyrproject-rtos%2Fzephyr%2Fpull%2F27737%2Fcommits%2F25e
1
9f
5b4e4ef07b1598104a02c4722386f2f17b&amp;data=04%7C01%7Chake.huang%40
n
xp
.com%7C3753d08aba3a4799ddb008d8dda294b0%7C686ea1d3bc2b4c6fa92cd99c5c301635
%7C0%7C0%7C637503037637038943%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAi
LCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=wp3iDOFIDk
csLjHRqk9OMWe3yiDfBXko6SHkIDrjQeA%3D&amp;reserved=0 two helper APIs is
added dma_api_request_channel request_channel; dma_api_release_channel
release_channel; the two APIs are for DMA engine which is capable to
dynamically allocate its channels to different DMA requests. and a filter
is also added in case of special DMA channel features.

Slack topic discussion is here

Can this topic be scheduled in next API meeting? Thanks.


Regards,
Hake
I wonder if we should pull this into a separate PR. I think a fair
amount of the code for these APIs could be generic.

For example I think we can use some of the generic devicetree
properties in "dts/bindings/dma/dma-controller.yaml”. The number space
allocation code seems pretty generic, even if it just library code used by
all the drivers.

- k







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