[PATCH i-g-t 1/2] pipe_crc: Warn if the CRC values is 0xffffffff

[PATCH i-g-t 1/2] pipe_crc: Warn if the CRC values is 0xffffffff

[Damien Lespiau]

This is what we read when the CRC logic in in a powered down well. We
really don't want that to happen.

In theory, it's possible 0xffffffff to be a valid CRC value, so I don't
assert here.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
---
 lib/igt_debugfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index 2f655a1..5c4bbc5 100644
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -199,9 +199,14 @@ bool igt_crc_is_null(igt_crc_t *crc)
 {
 	int i;
 
-	for (i = 0; i < crc->n_words; i++)
+	for (i = 0; i < crc->n_words; i++) {
+		if (crc->crc[i] == 0xffffffff)
+			igt_warn("Suspicious CRC: it looks like the CRC "
+				 "read back was from a register in a powered "
+				 "down well\n");
 		if (crc->crc[i])
 			return false;
+	}
 
 	return true;
 }
-- 
1.8.3.1

[PATCH i-g-t 2/2] pipe_crc: Make collect_crc() ensure the CRC looks somewhat valid

[Damien Lespiau]

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
---
 lib/igt_debugfs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index 5c4bbc5..d4a6cf6 100644
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -527,6 +527,8 @@ void igt_pipe_crc_collect_crc(igt_pipe_crc_t *pipe_crc, igt_crc_t *out_crc)
 	igt_pipe_crc_start(pipe_crc);
 	read_one_crc(pipe_crc, out_crc);
 	igt_pipe_crc_stop(pipe_crc);
+
+	igt_assert(!igt_crc_is_null(out_crc));
 }
 
 /*
-- 
1.8.3.1

Re: [PATCH i-g-t 1/2] pipe_crc: Warn if the CRC values is 0xffffffff

[Daniel Vetter]

On Mon, Jul 07, 2014 at 06:03:29PM +0100, Damien Lespiau wrote:
> This is what we read when the CRC logic in in a powered down well. We
> really don't want that to happen.
> 
> In theory, it's possible 0xffffffff to be a valid CRC value, so I don't
> assert here.

I think we  also should go through all tests and make sure that we change
all color channels of for crc based tests to use the full crc space. That
aside, ack on both patches.
-Daniel

> 
> Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
> ---
>  lib/igt_debugfs.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
> index 2f655a1..5c4bbc5 100644
> --- a/lib/igt_debugfs.c
> +++ b/lib/igt_debugfs.c
> @@ -199,9 +199,14 @@ bool igt_crc_is_null(igt_crc_t *crc)
>  {
>  	int i;
>  
> -	for (i = 0; i < crc->n_words; i++)
> +	for (i = 0; i < crc->n_words; i++) {
> +		if (crc->crc[i] == 0xffffffff)
> +			igt_warn("Suspicious CRC: it looks like the CRC "
> +				 "read back was from a register in a powered "
> +				 "down well\n");
>  		if (crc->crc[i])
>  			return false;
> +	}
>  
>  	return true;
>  }
> -- 
> 1.8.3.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch