linux-kernel - Re: [PATCH v7 01/33] xhci: add support to allocate several interrupters

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Date:   Wed, 4 Oct 2023 17:02:06 +0300
From:   Mathias Nyman <mathias.nyman@...el.com>
To:     Wesley Cheng <quic_wcheng@...cinc.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        gregkh@...uxfoundation.org, lgirdwood@...il.com,
        broonie@...nel.org, perex@...ex.cz, tiwai@...e.com,
        agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, srinivas.kandagatla@...aro.org,
        bgoswami@...cinc.com, Thinh.Nguyen@...opsys.com
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        alsa-devel@...a-project.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v7 01/33] xhci: add support to allocate several
 interrupters

On 2.10.2023 23.07, Wesley Cheng wrote:
> Hi Mathias,
> 
> On 9/28/2023 3:31 AM, Mathias Nyman wrote:
>> On 22.9.2023 0.48, Wesley Cheng wrote:
>>> From: Mathias Nyman <mathias.nyman@...ux.intel.com>
>>>
>>> Modify the XHCI drivers to accommodate for handling multiple event rings in
>>> case there are multiple interrupters.  Add the required APIs so clients are
>>> able to allocate/request for an interrupter ring, and pass this information
>>> back to the client driver.  This allows for users to handle the resource
>>> accordingly, such as passing the event ring base address to an audio DSP.
>>> There is no actual support for multiple MSI/MSI-X vectors.
>>>
>>> Factoring out XHCI interrupter APIs and structures done by Wesley Cheng, in
>>> order to allow for USB class drivers to utilze them.
>>>
>>>   }
>>> +void xhci_remove_secondary_interrupter(struct usb_hcd *hcd, struct xhci_interrupter *ir)
>>> +{
>>> +    struct xhci_hcd *xhci = hcd_to_xhci(hcd);
>>> +    unsigned int intr_num;
>>> +
>>> +    /* interrupter 0 is primary interrupter, don't touchit */
>>> +    if (!ir || !ir->intr_num || ir->intr_num >= xhci->max_interrupters) {
>>> +        xhci_dbg(xhci, "Invalid secondary interrupter, can't remove\n");
>>> +        return;
>>> +    }
>>> +
>>> +    /* fixme, should we check xhci->interrupter[intr_num] == ir */
>>> +    spin_lock(&xhci->lock);
>>
>> Needs to be spin_lock_irq() ir spin_lock_irqsave() as xhci->lock is used in interrupt handler.
>>
>>
>>> +    intr_num = ir->intr_num;
>>> +    xhci_free_interrupter(xhci, ir);
>>> +    xhci->interrupters[intr_num] = NULL;
>>> +    spin_unlock(&xhci->lock);
>>
>> likewise
>>
> 
> Let me check these again.  In general, I think I will use both the xhci->mutex and 
> xhci->lock where needed, because I believe we'd run into sleep while atomic issues
> while freeing the DMA memory.  Will rework this and submit in the next rev.
> 

Maybe we need to split xhci_free_interrupter() into separate remove and free functions

Did some work on this, and on the sideband api in general.

Code still has a lot of FIXMEs, and it's completely untested, but to avoid us
from doing duplicate work I pushed it to my feature_interrupters branch anyway

git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git feature_interrupters
https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=feature_interrupters

Thanks
-Mathias