[PATCH 1/1] i3c: master: svc: Flush FIFO before sending Dynamic Address Assignment(DAA)

[PATCH 1/1] i3c: master: svc: Flush FIFO before sending Dynamic Address Assignment(DAA)

[Frank Li]

Ensure the FIFO is empty before issuing the DAA command to prevent
incorrect command data from being sent. Align with other data transfers,
such as svc_i3c_master_start_xfer_locked(), which flushes the FIFO before
sending a command.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Hotplug stress test find a wrong byte send out, this patch can resolve
this issue although have not identify which operation cause a byte left in
FIFO.
---
 drivers/i3c/master/svc-i3c-master.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
index c1ee3828e7eec..bb660c4dcce56 100644
--- a/drivers/i3c/master/svc-i3c-master.c
+++ b/drivers/i3c/master/svc-i3c-master.c
@@ -892,6 +892,8 @@ static int svc_i3c_master_do_daa_locked(struct svc_i3c_master *master,
 	u32 reg;
 	int ret, i;
 
+	svc_i3c_master_flush_fifo(master);
+
 	while (true) {
 		/* clean SVC_I3C_MINT_IBIWON w1c bits */
 		writel(SVC_I3C_MINT_IBIWON, master->regs + SVC_I3C_MSTATUS);
-- 
2.34.1


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Re: [PATCH 1/1] i3c: master: svc: Flush FIFO before sending Dynamic Address Assignment(DAA)

[Miquel Raynal]

On 29/01/2025 at 11:22:50 -05, Frank Li <Frank.Li@nxp.com> wrote:

> Ensure the FIFO is empty before issuing the DAA command to prevent
> incorrect command data from being sent. Align with other data transfers,
> such as svc_i3c_master_start_xfer_locked(), which flushes the FIFO before
> sending a command.
>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> Hotplug stress test find a wrong byte send out, this patch can resolve
> this issue although have not identify which operation cause a byte left in
> FIFO.

That's exactly what I understood from your commit log, I have mixed
feelings about the patch because it probably hides something bigger. Not
that I want to break users, but there is likely something else to do to
avoid it. Is there any chance you can check the content of the FIFO and
warn before flushing (at least while debugging)?

Anyway,

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>

Thanks,
Miquèl

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Re: [PATCH 1/1] i3c: master: svc: Flush FIFO before sending Dynamic Address Assignment(DAA)

[Frank Li]

On Fri, Jan 31, 2025 at 09:52:48AM +0100, Miquel Raynal wrote:
> On 29/01/2025 at 11:22:50 -05, Frank Li <Frank.Li@nxp.com> wrote:
>
> > Ensure the FIFO is empty before issuing the DAA command to prevent
> > incorrect command data from being sent. Align with other data transfers,
> > such as svc_i3c_master_start_xfer_locked(), which flushes the FIFO before
> > sending a command.
> >
> > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > ---
> > Hotplug stress test find a wrong byte send out, this patch can resolve
> > this issue although have not identify which operation cause a byte left in
> > FIFO.
>
> That's exactly what I understood from your commit log, I have mixed
> feelings about the patch because it probably hides something bigger. Not
> that I want to break users, but there is likely something else to do to
> avoid it. Is there any chance you can check the content of the FIFO and
> warn before flushing (at least while debugging)?

Yes, it is random data. We find this problem at some month ago. Still not
identify why some data left in FIFO. Because it only one byte in FIFO, it
hard to find pattern to identify where.

Frank

>
> Anyway,
>
> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
>
> Thanks,
> Miquèl

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Re: [PATCH 1/1] i3c: master: svc: Flush FIFO before sending Dynamic Address Assignment(DAA)

[Alexandre Belloni]

On Wed, 29 Jan 2025 11:22:50 -0500, Frank Li wrote:
> Ensure the FIFO is empty before issuing the DAA command to prevent
> incorrect command data from being sent. Align with other data transfers,
> such as svc_i3c_master_start_xfer_locked(), which flushes the FIFO before
> sending a command.
> 
> 

Applied, thanks!

[1/1] i3c: master: svc: Flush FIFO before sending Dynamic Address Assignment(DAA)
      https://git.kernel.org/abelloni/c/a892ee4cf22a

Best regards,

-- 
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Embedded Linux and Kernel engineering
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