linux-kernel - Re: [PATCH V4 XDMA 2/2] dmaengine: xilinx: xdma: Add user logic interrupt support

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Message-ID: <5f77987e-49bc-e035-19e0-52c25f4adc7e@amd.com>
Date:   Tue, 27 Sep 2022 10:18:54 -0700
From:   Lizhi Hou <lizhi.hou@....com>
To:     Martin Tůma <tumic@...see.org>,
        <vkoul@...nel.org>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <trix@...hat.com>
CC:     <max.zhen@....com>, <sonal.santan@....com>, <larry.liu@....com>,
        <brian.xu@....com>
Subject: Re: [PATCH V4 XDMA 2/2] dmaengine: xilinx: xdma: Add user logic
 interrupt support


On 9/27/22 09:46, Martin Tůma wrote:
> On 27. 09. 22 18:28, Lizhi Hou wrote:
>
>> Okay, I got the point. How about changing request/remove APIs to 
>> enable/disable APIs as below
>>
>>       xdma_enable_user_irq(struct platform_device *pdev, u32 
>> user_irq_index, u32 *irq)
>>
>>              user_irq_index: user logic interrupt wire index. (XDMA 
>> driver determines how system IRQs are mapped to DMA channels and user 
>> logic wires)
>>
>>              irq: IRQ number returned for registering interrupt 
>> handler (request_irq()) or passing to existing platform driver.
>>
>>      xdma_disable_user_irq(struct platform_device *pdev, u32 
>> user_irq_index)
>>
>> Does this make sense to you?
>>
>
> I think even the "irq" parameter in the enable function is surplus as 
> the parent driver (the driver of the actual PCIe card) knows* what PCI 
> irq he has to allocate without XDMA providing the number.
>
> xdma_enable_user_irq(struct platform_device *pdev, u32 user_irq_index);
> xdma_disable_user_irq(struct platform_device *pdev, u32 user_irq_index);
>
> should be all that is needed.
>
> M.
>
> * something like:
> pci_irq_vector((pdev), PCI_BAR_ID) + NUM_C2H_CHANNELS + NUM_H2C_CHANNELS
> can be used from the PCIe driver

How does parent driver know the first few vectors will be assigned to 
DMA channel?  Parent diver should not assume the first 
(NUM_C2H_CHANNELS+NUM_H2C_CHANNELS) are for DMA channel.

Parent driver passes the system IRQ range  to XDMA driver, and only XDMA 
driver knows what IRQs are used by DMA channel and what IRQs are mapped 
to user logic wires. I would keep the "u32 *irq" argument.


Thanks,

Lizhi