linux-kernel - Re: [PATCH] dmaengine: ti: k3-udma-glue: do not create glue dma devices for udma channels

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Date:   Wed, 5 Apr 2023 10:30:50 +0530
From:   Siddharth Vadapalli <s-vadapalli@...com>
To:     Péter Ujfalusi <peter.ujfalusi@...il.com>,
        Vignesh Raghavendra <vigneshr@...com>
CC:     <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <srk@...com>,
        <vkoul@...nel.org>, <s-vadapalli@...com>
Subject: Re: [PATCH] dmaengine: ti: k3-udma-glue: do not create glue dma
 devices for udma channels

Péter, Vignesh,

Thank you for reviewing the patch.

On 05/04/23 09:17, Vignesh Raghavendra wrote:
> 
> On 05/04/23 01:53, Péter Ujfalusi wrote:
>>
>>
>> On 04/04/2023 11:11, Siddharth Vadapalli wrote:
>>> From: Grygorii Strashko <grygorii.strashko@...com>
>>>
>>> In case K3 DMA glue layer is using UDMA channels (AM65/J721E/J7200) it
>>> doesn't need to create own DMA devices per RX/TX channels as they are
>>> never
>>> used and just waste resources. The UDMA based platforms are coherent and
>>> UDMA device iteslf is used for DMA memory management.
>>>
>>> Hence, update K3 DMA glue layer to create K3 DMA glue DMA devices per
>>> RX/TX
>>> channels only in case of PKTDMA (AM64) where coherency configurable
>>> per DMA
>>> channel.
>>>
>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>>> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
>>> ---
>>>   drivers/dma/ti/k3-udma-glue.c | 70 +++++++++++++++++------------------
>>>   1 file changed, 34 insertions(+), 36 deletions(-)
>>>
>>> diff --git a/drivers/dma/ti/k3-udma-glue.c
>>> b/drivers/dma/ti/k3-udma-glue.c
>>> index 789193ed0386..b0c9572b0d02 100644
>>> --- a/drivers/dma/ti/k3-udma-glue.c
>>> +++ b/drivers/dma/ti/k3-udma-glue.c
>>> @@ -293,19 +293,18 @@ struct k3_udma_glue_tx_channel
>>> *k3_udma_glue_request_tx_chn(struct device *dev,
>>>       }
>>>       tx_chn->udma_tchan_id = xudma_tchan_get_id(tx_chn->udma_tchanx);
>>>   -    tx_chn->common.chan_dev.class = &k3_udma_glue_devclass;
>>> -    tx_chn->common.chan_dev.parent =
>>> xudma_get_device(tx_chn->common.udmax);
>>> -    dev_set_name(&tx_chn->common.chan_dev, "tchan%d-0x%04x",
>>> -             tx_chn->udma_tchan_id, tx_chn->common.dst_thread);
>>> -    ret = device_register(&tx_chn->common.chan_dev);
>>> -    if (ret) {
>>> -        dev_err(dev, "Channel Device registration failed %d\n", ret);
>>> -        put_device(&tx_chn->common.chan_dev);
>>> -        tx_chn->common.chan_dev.parent = NULL;
>>> -        goto err;
>>> -    }
>>> -
>>>       if (xudma_is_pktdma(tx_chn->common.udmax)) {
>>
>> it might be possible to narrow it down to include a test for atype_asel
>> 14 or 15, but then I would move that test to a helper (passing common as
>> parameter) and re-use it in other places to avoid getting out o sync
>> overtime.
>> Might not worth the effort, just an observation.
> 
> Irrespective, we should at least add check for atype_asel == 14/15 along
> with xudma_is_pktdma().
> 
> Refractoring these checks to separate function can be patch of its own
> 
>>
>>> +        tx_chn->common.chan_dev.class = &k3_udma_glue_devclass;
>>> +        tx_chn->common.chan_dev.parent =
>>> xudma_get_device(tx_chn->common.udmax);
>>> +        dev_set_name(&tx_chn->common.chan_dev, "tchan%d-0x%04x",
>>> +                 tx_chn->udma_tchan_id, tx_chn->common.dst_thread);
>>> +        ret = device_register(&tx_chn->common.chan_dev);
>>> +        if (ret) {
>>> +            dev_err(dev, "Channel Device registration failed %d\n",
>>> ret);
>>
>> my guess is that the put_device() is still needed, no?
> 
> Agree

I will fix this at all 3 occurrences and post the v2 patch.

> 
>>
>>> +            tx_chn->common.chan_dev.parent = NULL;
>>> +            goto err;
>>> +        }
>>> +
>>>           /* prepare the channel device as coherent */
> 
> [...]
> 

-- 
Regards,
Siddharth.