[PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller
daniel.thompson at linaro.org
Thu Oct 8 05:28:29 PDT 2015
On 08/10/15 13:05, chunfeng yun wrote:
> On Thu, 2015-10-01 at 12:44 +0100, Daniel Thompson wrote:
>> On 29/09/15 04:01, Chunfeng Yun wrote:
>>> There some vendor quirks for MTK xhci host controller:
>>> 1. It defines some extra SW scheduling parameters for HW
>>> to minimize the scheduling effort for synchronous and
>>> interrupt endpoints. The parameters are put into reseved
>>> DWs of slot context and endpoint context.
>>> 2. Its IMODI unit for Interrupter Moderation register is
>>> 8 times as much as that defined in xHCI spec.
>>> 3. Its TDS in Normal TRB defines a number of packets that
>>> remains to be transferred for a TD after processing all
>>> Max packets in all previous TRBs.
>>> Signed-off-by: Chunfeng Yun <chunfeng.yun at mediatek.com>
>> I've done some basic soak tests, both with a directly attached USB3 HDD
>> and, given the extra code to manage isochronous xfer, also with a hub,
>> disc and two audio interfaces.
>> Tested-by: Daniel Thompson <daniel.thompson at linaro.org>
>>> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
>>> index 57f40a1..243f696 100644
>>> --- a/drivers/usb/host/xhci-ring.c
>>> +++ b/drivers/usb/host/xhci-ring.c
>>> @@ -68,6 +68,7 @@
>>> #include <linux/slab.h>
>>> #include "xhci.h"
>>> #include "xhci-trace.h"
>>> +#include "xhci-mtk.h"
>>> * Returns zero if the TRB isn't in this segment, otherwise it returns the DMA
>>> @@ -3044,18 +3045,27 @@ static u32 xhci_td_remainder(struct xhci_hcd *xhci, int transferred,
>>> struct urb *urb, unsigned int num_trbs_left)
>>> u32 maxp, total_packet_count;
>>> + u32 skip_current_trb = 0;
>> A bit of a nitpick but why do we need skip_current_trb? Testing
>> (xhci->quirks & XHCI_MTK_HOST) twice would make what the code does, and
>> why, more obvious.
> I am not sure which way it is better, so add variable of
> skip_current_trb to reduce test times.
I can't imagine either approach impacts performance. However introducing
skip_current_trb makes the flow of the branches harder to follow.
The first branch was a version check and can remain so; we only need to
do something special with the quirks because the MTK controller is 0.97
but with a few bits added:
/* MTK xHCI is mostly 0.97 but contains some features from 1.0 */
if (xhci->hci_version < 0x100 && !(xhci->quirks & XHCI_MTK_HOST))
Setting trb_buff_len to zero is accommodating a quirk and this is
clearer when we have:
/* for MTK xHCI, TD size doesn't include this TRB */
if (xhci->quirks & XHCI_MTK_HOST)
trb_buff_len = 0;
>> Anyhow with that looked at, and the caveat that I'm not much of USB
>> expert, you're welcome to add my Reviewed-by: to v10.
> Thanks a lot
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