linux-kernel - Re: [RFC] usb: host: xhci-mem: Write high first on erst base of secondary interrupter

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Message-ID: <20240527024950.GA146722@ubuntu>
Date: Mon, 27 May 2024 11:49:50 +0900
From: Jung Daehwan <dh10.jung@...sung.com>
To: Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc: Mathias Nyman <mathias.nyman@...el.com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, "open list:USB XHCI DRIVER"
	<linux-usb@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>, Thinh
	Nguyen <Thinh.Nguyen@...opsys.com>
Subject: Re: [RFC] usb: host: xhci-mem: Write high first on erst base of
 secondary interrupter

On Thu, May 23, 2024 at 04:38:48PM +0300, Mathias Nyman wrote:
> On 23.5.2024 7.43, Jung Daehwan wrote:
> >On Wed, May 22, 2024 at 04:40:56PM +0300, Mathias Nyman wrote:
> >>On 22.5.2024 4.03, Daehwan Jung wrote:
> >>>ERSTBA_HI should be written first on secondary interrupter.
> >>>That's why secondary interrupter could be set while Host Controller
> >>>is already running.
> >>>
> >>>[Synopsys]- The host controller was design to support ERST setting
> >>>during the RUN state. But since there is a limitation in controller
> >>>in supporting separate ERSTBA_HI and ERSTBA_LO programming,
> >>>It is supported when the ERSTBA is programmed in 64bit,
> >>>or in 32 bit mode ERSTBA_HI before ERSTBA_LO
> >>
> >>xHCI specification 5.1 "Register Conventions "states that 64 bit
> >>registers should be written in low-high order
> >>
> >>>
> >>>[Synopsys]- The internal initialization of event ring fetches
> >>>the "Event Ring Segment Table Entry" based on the indication of
> >>>ERSTBA_LO written.
> >>>
> >>
> >>Any idea if this is a common issue with this host?
> >>Should other 64 bit registers also be written in reverse order.
> >>
> >>>Signed-off-by: Daehwan Jung <dh10.jung@...sung.com>
> >>>---
> >>>  drivers/usb/host/xhci-mem.c | 5 ++++-
> >>>  drivers/usb/host/xhci.h     | 6 ++++++
> >>>  2 files changed, 10 insertions(+), 1 deletion(-)
> >>>
> >>>diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> >>>index 3100219..36ee704 100644
> >>>--- a/drivers/usb/host/xhci-mem.c
> >>>+++ b/drivers/usb/host/xhci-mem.c
> >>>@@ -2325,7 +2325,10 @@ xhci_add_interrupter(struct xhci_hcd *xhci, struct xhci_interrupter *ir,
> >>>  	erst_base = xhci_read_64(xhci, &ir->ir_set->erst_base);
> >>>  	erst_base &= ERST_BASE_RSVDP;
> >>>  	erst_base |= ir->erst.erst_dma_addr & ~ERST_BASE_RSVDP;
> >>>-	xhci_write_64(xhci, erst_base, &ir->ir_set->erst_base);
> >>>+	if (intr_num == 0)
> >>>+		xhci_write_64(xhci, erst_base, &ir->ir_set->erst_base);
> >>>+	else
> >>>+		xhci_write_64_r(xhci, erst_base, &ir->ir_set->erst_base);
> >>
> >>This may cause issues with other hosts expecting low-high order as stated
> >>in the specification.
> >>
> >>If all 64 bit registers should be written in high-low order for this host then
> >>maybe set a quirk flag and change xhci_write_64()instead.
> >>
> >>xhci_write_64(...)
> >>{
> >>	if (xhci->quirks & XHCI_WRITE_64_HI_LO)
> >>		hi_lo_writeq(val, regs);
> >>	else
> >>		lo_hi_writeq(val, regs);
> >>}
> >>
> >
> >Mathias, Thanks for the comment.
> >
> >I've seen this issue only writing the base address of ERST.
> >It's better to use a quirk flag as you said.
> >How about using the quirk only in xhci_add_interrupter?
> >
> >@@ -2325,7 +2325,10 @@ xhci_add_interrupter(struct xhci_hcd *xhci, struct xhci_interrupter *ir,
> >   	erst_base = xhci_read_64(xhci, &ir->ir_set->erst_base);
> >   	erst_base &= ERST_BASE_RSVDP;
> >   	erst_base |= ir->erst.erst_dma_addr & ~ERST_BASE_RSVDP;
> >	xhci_write_64(xhci, erst_base, &ir->ir_set->erst_base);
> >  	if (xhci->quirks & XHCI_WRITE_64_HI_LO)
> >		xhci_write_64_r(xhci, erst_base, &ir->ir_set->erst_base);
> >	else
> >		xhci_write_64(xhci, erst_base, &ir->ir_set->erst_base);
> >
> 
> This works.
> Maybe even skip the xhci_write_64_r() helper and just use hi_lo_writeq() directly.
> 
> Thanks
> Mathias
> 
> 

Thanks. I will send the quirk patch soon.

Best Regards,
Jung Daehwan

> 
>