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Re: [PATCH v3 01/10] drivers/char: Add support for USB3 DbC debugger
- To: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 5 Aug 2022 11:54:06 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Fri, 05 Aug 2022 09:54:14 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 05.08.2022 11:51, Marek Marczykowski-Górecki wrote:
> On Fri, Aug 05, 2022 at 09:23:32AM +0200, Jan Beulich wrote:
>> On 26.07.2022 05:23, Marek Marczykowski-Górecki wrote:
>>> +static struct xhci_trb evt_trb[DBC_TRB_RING_CAP];
>>> +static struct xhci_trb out_trb[DBC_TRB_RING_CAP];
>>> +static struct xhci_trb in_trb[DBC_TRB_RING_CAP];
>>> +static struct xhci_erst_segment erst __aligned(64);
>>> +static struct xhci_dbc_ctx ctx __aligned(64);
>>> +static uint8_t out_wrk_buf[DBC_WORK_RING_CAP] __aligned(DBC_PAGE_SIZE);
>>
>> I've been trying to identify the reason for the alignment here,
>> compared to the other buffers which are no longer page-aligned. I
>> haven't even been able to locate the place where the address of
>> this buffer is actually written to hardware; all I could find was
>> the respective virt_to_maddr(). Could you please point me at that?
>
> It's dbc_flush() -> dbc_push_trb().
> And indeed, I think I can drop the alignment when it's moved into
> structure dedicated for DMA-accessible buffers.
Why would you be able to drop the alignment then, but not here?
Jan
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