Re: [PATCH] Revert 95f408bb Ryzen DMA related RiSC engine stall fixes

[Mauro Carvalho Chehab <mchehab@kernel.org>]

Em Sun, 21 Oct 2018 15:45:39 +0200
Markus Dobel <markus.dobel@gmx.de> escreveu:

> The original commit (the one reverted in this patch) introduced a 
> regression,
> making a previously flawless adapter unresponsive after running a few 
> hours
> to days. Since I never experienced the problems that the original commit 
> is
> supposed to fix, I propose to revert the change until a regression-free
> variant is found.
> 
> Before submitting this, I've been running a system 24x7 with this revert 
> for
> several weeks now, and it's running stable again.
> 
> It's not a pure revert, as the original commit does not revert cleanly
> anymore due to other changes, but content-wise it is.
> 
> Signed-off-by: Markus Dobel <markus.dobel@gmx.de>
> ---
>   drivers/media/pci/cx23885/cx23885-core.c | 60 ------------------------
>   drivers/media/pci/cx23885/cx23885-reg.h  | 14 ------
>   2 files changed, 74 deletions(-)
> 
> diff --git a/drivers/media/pci/cx23885/cx23885-core.c 
> b/drivers/media/pci/cx23885/cx23885-core.c
> index 39804d830305..606f6fc0e68b 100644
> --- a/drivers/media/pci/cx23885/cx23885-core.c
> +++ b/drivers/media/pci/cx23885/cx23885-core.c
> @@ -601,25 +601,6 @@ static void cx23885_risc_disasm(struct 
> cx23885_tsport *port,

Patch was mangled by your e-mailer: it broke longer lines, causing
it to not apply.

Also, before just reverting the entire thing, could you please check
if the enclosed hack would solve it?

If so, it should be easy to add a quirk at drivers/pci/quirks.c
in order to detect the Ryzen models with a bad DMA engine that
require periodic resets, and then make cx23885 to use it.

We did similar tricks before with some broken DMA engines, at
the time we had overlay support on drivers and AMD controllers
didn't support PCI2PCI DMA transfers.

Brad,

Could you please address this issue?


diff --git a/drivers/media/pci/cx23885/cx23885-core.c b/drivers/media/pci/cx23885/cx23885-core.c
index 39804d830305..8b012bee6b32 100644
--- a/drivers/media/pci/cx23885/cx23885-core.c
+++ b/drivers/media/pci/cx23885/cx23885-core.c
@@ -603,8 +603,14 @@ static void cx23885_risc_disasm(struct cx23885_tsport *port,
 
 static void cx23885_clear_bridge_error(struct cx23885_dev *dev)
 {
-	uint32_t reg1_val = cx_read(TC_REQ); /* read-only */
-	uint32_t reg2_val = cx_read(TC_REQ_SET);
+	uint32_t reg1_val, reg2_val;
+
+	/* TODO: check for Ryzen quirk */
+	if (1)
+		return;
+
+	reg1_val = cx_read(TC_REQ); /* read-only */
+	reg2_val = cx_read(TC_REQ_SET);
 
 	if (reg1_val && reg2_val) {
 		cx_write(TC_REQ, reg1_val);



Thanks,
Mauro