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From: Sanjay R Mehta <sanmehta@amd.com>
To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Sanjay R Mehta <Sanju.Mehta@amd.com>,
	andreas.noever@gmail.com, michael.jamet@intel.com,
	YehezkelShB@gmail.com, Basavaraj.Natikar@amd.com,
	linux-usb@vger.kernel.org, "Shah,
	Nehal-bakulchandra" <Nehal-bakulchandra.Shah@amd.com>,
	Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Subject: Re: [PATCH v2 2/4] thunderbolt: Handle ring interrupt by reading intr status
Date: Thu, 5 Aug 2021 23:33:10 +0530	[thread overview]
Message-ID: <a1a30df7-3218-985c-d379-b8d042d8c9c8@amd.com> (raw)
In-Reply-To: <YQv5t3OlaMxT/w0o@lahna>



On 8/5/2021 8:16 PM, Mika Westerberg wrote:
> [CAUTION: External Email]
> 
> On Thu, Aug 05, 2021 at 05:19:39PM +0300, Mika Westerberg wrote:
>> On Thu, Aug 05, 2021 at 06:29:36PM +0530, Sanjay R Mehta wrote:
>>>
>>>
>>> On 8/4/2021 9:18 PM, Mika Westerberg wrote:
>>>> [CAUTION: External Email]
>>>>
>>>> Hi,
>>>>
>>>> On Tue, Aug 03, 2021 at 07:34:54AM -0500, Sanjay R Mehta wrote:
>>>>> From: Sanjay R Mehta <sanju.mehta@amd.com>
>>>>>
>>>>> As per USB4 spec by default "Disable ISR Auto-Clear" bit is set to 0,
>>>>> and the Tx/Rx ring interrupt status is needs to be cleared.
>>>>>
>>>>> Hence handling it by reading the "Interrupt status" register in the ISR.
>>>>>
>>>>> Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
>>>>> Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
>>>>> ---
>>>>>  drivers/thunderbolt/nhi.c | 14 ++++++++++++++
>>>>>  1 file changed, 14 insertions(+)
>>>>>
>>>>> diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
>>>>> index ef01aa6..7ad2202 100644
>>>>> --- a/drivers/thunderbolt/nhi.c
>>>>> +++ b/drivers/thunderbolt/nhi.c
>>>>> @@ -373,11 +373,25 @@ void tb_ring_poll_complete(struct tb_ring *ring)
>>>>>  }
>>>>>  EXPORT_SYMBOL_GPL(tb_ring_poll_complete);
>>>>>
>>>>> +static void check_and_clear_intr_status(struct tb_ring *ring)
>>>>> +{
>>>>> +     if (!(ring->nhi->pdev->vendor == PCI_VENDOR_ID_INTEL)) {
>>>>> +             if (ring->is_tx)
>>>>> +                     ioread32(ring->nhi->iobase
>>>>> +                              + REG_RING_NOTIFY_BASE);
>>>>> +             else
>>>>> +                     ioread32(ring->nhi->iobase
>>>>> +                              + REG_RING_NOTIFY_BASE
>>>>> +                              + 4 * (ring->nhi->hop_count / 32));
>>>>> +     }
>>>>> +}
>>>>
>>>> I'm now playing with this series on Intel hardware. I wanted to check
>>>> from you whether the AMD controller implements the Auto-Clear feature? I
>>>> mean if we always clear bit 17 of the Host Interface Control register do
>>>> you still need to call the above or it is cleared automatically?
>>>>
>>> Yes, AMD implements Auto-Clear and a read operation is required to clear
>>> the interrupt status.
>>>
>>> It is explicitly described in the Spec, Section "12.6.3.4.1 -> "Table
>>> 12-27. Interrupt Status" as below
>>>
>>> "If the Disable ISR Auto-Clear bit is set to 0b, then a read operation
>>> returns the current value and then clears the register to 0."
>>
>> D'oh, right. It is about auto clear of the ISS register on read or not.
>> I misunderstood the whole bit.
>>
>>>
>>>> I'm hoping that we could make this work on all controllers without too
>>>> many special cases ;-)
>>>
>>> Will it be good idea to have a separate variable in "struct tb_nhi" as
>>> "nhi->is_intr_autoclr" so that we can set in the
>>> "quirk_enable_intr_auto_clr()" as required which can be used in above
>>> check_and_clear_intr_status() function instead of vendor check.
>>
>> Probably that would work better. Let me try to figure out if we can
>> somehow do the same in Intel controller too so we would only have single
>> path here.
> 
> Looks like we cannot get it working without quirk of some kind :( I
> think we can do this:
> 
>   1. Add nhi_check_quirks() to nhi.c and that one checks for
>      PCI_VENDOR_ID_INTEL and sets nhi->quirks |= DMA_MISC_INT_AUTO_CLEAR.
>   2. Then check it in both ring_interrupt_active() and in
>      ring_clear_msix(ring) and if set handle the case accordingly.
> 
> Let's add nhi->quirks directly now because I have a feeling that we may
> need additional flags in the future ;-)
> 
> Would you like to update this series with the above changes or you want
> me to do that?

Sounds good. Sure, I will update this series as per your suggestion.
Thank you :)
> 

  reply	other threads:[~2021-08-05 18:03 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-03 12:34 [PATCH v2 0/4] Added some bug fixes for USB4 Sanjay R Mehta
2021-08-03 12:34 ` [PATCH v2 1/4] thunderbolt: Intel controller uses BIT(2) for intr auto Sanjay R Mehta
2021-08-03 12:34 ` [PATCH v2 2/4] thunderbolt: Handle ring interrupt by reading intr status Sanjay R Mehta
2021-08-04 15:48   ` Mika Westerberg
2021-08-05 12:56     ` Mika Westerberg
2021-08-05 13:06       ` Sanjay R Mehta
2021-08-05 14:20         ` Mika Westerberg
2021-08-05 12:59     ` Sanjay R Mehta
2021-08-05 14:19       ` Mika Westerberg
2021-08-05 14:46         ` Mika Westerberg
2021-08-05 18:03           ` Sanjay R Mehta [this message]
2021-08-03 12:34 ` [PATCH v2 3/4] thunderbolt: Skip port init for control adapter(0) Sanjay R Mehta
2021-08-03 12:34 ` [PATCH v2 4/4] thunderbolt: Fix port linking by checking all adapters Sanjay R Mehta

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