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Message-ID: <4752203.GXAFRqVoOG@jernej-laptop>
Date: Sat, 05 Nov 2022 20:48:35 +0100
From: Jernej Škrabec <jernej.skrabec@...il.com>
To: Chen-Yu Tsai <wens@...e.org>, Samuel Holland <samuel@...lland.org>
Cc: Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-sunxi@...ts.linux.dev, Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH 2/2] bus: sunxi-rsb: Support atomic transfers
Dne sobota, 05. november 2022 ob 20:46:47 CET je Jernej Škrabec napisal(a):
> Dne sobota, 05. november 2022 ob 20:19:53 CET je Samuel Holland napisal(a):
> > When communicating with a PMIC during system poweroff (pm_power_off()),
> > IRQs are disabled and we are in a RCU read-side critical section, so we
> > cannot use wait_for_completion_io_timeout(). Instead, poll the status
> > register for transfer completion.
> >
> > Signed-off-by: Samuel Holland <samuel@...lland.org>
Also a fixes tag would be in order here.
Best regards,
Jernej
> > ---
> >
> > drivers/bus/sunxi-rsb.c | 23 +++++++++++++++++------
> > 1 file changed, 17 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/bus/sunxi-rsb.c b/drivers/bus/sunxi-rsb.c
> > index 17343cd75338..0f0e498d4379 100644
> > --- a/drivers/bus/sunxi-rsb.c
> > +++ b/drivers/bus/sunxi-rsb.c
> > @@ -267,6 +267,9 @@ EXPORT_SYMBOL_GPL(sunxi_rsb_driver_register);
> >
> > /* common code that starts a transfer */
> > static int _sunxi_rsb_run_xfer(struct sunxi_rsb *rsb)
> > {
> >
> > + bool timeout;
> > + u32 status;
> > +
> >
> > if (readl(rsb->regs + RSB_CTRL) & RSB_CTRL_START_TRANS) {
> >
> > dev_dbg(rsb->dev, "RSB transfer still in progress\n");
> > return -EBUSY;
> >
> > @@ -279,8 +282,16 @@ static int _sunxi_rsb_run_xfer(struct sunxi_rsb *rsb)
> >
> > writel(RSB_CTRL_START_TRANS | RSB_CTRL_GLOBAL_INT_ENB,
> >
> > rsb->regs + RSB_CTRL);
> >
> > - if (!wait_for_completion_io_timeout(&rsb->complete,
> > -
>
> msecs_to_jiffies(100))) {
>
> > + if (irqs_disabled()) {
> > + timeout = readl_poll_timeout_atomic(rsb->regs +
>
> RSB_INTS,
>
> > + status,
>
> status, 10, 100000);
>
> It would be good to check only for RSB_INTS_LOAD_BSY, RSB_INTS_TRANS_ERR and
> RSB_INTS_TRANS_OVER flags and clear them afterwards. That way we avoid
> problems if this path is used outside power off case.
>
> Best regards,
> Jernej
>
> > + } else {
> > + timeout = !wait_for_completion_io_timeout(&rsb-
> >
> >complete,
> >
> > +
>
> msecs_to_jiffies(100));
>
> > + status = rsb->status;
> > + }
> > +
> > + if (timeout) {
> >
> > dev_dbg(rsb->dev, "RSB timeout\n");
> >
> > /* abort the transfer */
> >
> > @@ -292,18 +303,18 @@ static int _sunxi_rsb_run_xfer(struct sunxi_rsb
> > *rsb)
> >
> > return -ETIMEDOUT;
> >
> > }
> >
> > - if (rsb->status & RSB_INTS_LOAD_BSY) {
> > + if (status & RSB_INTS_LOAD_BSY) {
> >
> > dev_dbg(rsb->dev, "RSB busy\n");
> > return -EBUSY;
> >
> > }
> >
> > - if (rsb->status & RSB_INTS_TRANS_ERR) {
> > - if (rsb->status & RSB_INTS_TRANS_ERR_ACK) {
> > + if (status & RSB_INTS_TRANS_ERR) {
> > + if (status & RSB_INTS_TRANS_ERR_ACK) {
> >
> > dev_dbg(rsb->dev, "RSB slave nack\n");
> > return -EINVAL;
> >
> > }
> >
> > - if (rsb->status & RSB_INTS_TRANS_ERR_DATA) {
> > + if (status & RSB_INTS_TRANS_ERR_DATA) {
> >
> > dev_dbg(rsb->dev, "RSB transfer data
>
> error\n");
>
> > return -EIO;
> >
> > }
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