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SubjectRe: [PATCH v2 2/2] drm/etnaviv: print MMU exception cause
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On Fr, 2019-09-13 at 07:50 +0200, Christian Gmeiner wrote:
> Might be useful when debugging MMU exceptions.
>
> Changes in V2:
> - Use a static array of string for error message as suggested
> by Lucas Stach.

Please move those changelogs below the 3 dashes, so they don't end up
in the commit message. They don't really add any value to the
persistent kernel history.

> Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
> ---
> drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> index d47d1a8e0219..b8cd85153fe0 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> @@ -1351,6 +1351,15 @@ static void sync_point_worker(struct work_struct *work)
>
> static void dump_mmu_fault(struct etnaviv_gpu *gpu)
> {
> + static const char *errors[] = {
> + "slave not present",
> + "page not present",
> + "write violation",
> + "out of bound",
> + "read security violation",
> + "write security violation",
> + };
> +
> u32 status_reg, status;
> int i;
>
> @@ -1364,10 +1373,16 @@ static void dump_mmu_fault(struct etnaviv_gpu *gpu)
>
> for (i = 0; i < 4; i++) {
> u32 address_reg;
> + const char *error = "unknown state";
>
> if (!(status & (VIVS_MMUv2_STATUS_EXCEPTION0__MASK << (i * 4))))
> continue;
>
> + if (status < ARRAY_SIZE(errors))
> + error = errors[status];

Huh? This won't work. The status register is a bitfield, not an integer
so you need to map the bit position to the array index via ffs() or
something like that.

Regards,
Lucas

> +
> + dev_err_ratelimited(gpu->dev, "MMU %d %s\n", i, error);
> +
> if (gpu->sec_mode == ETNA_SEC_NONE)
> address_reg = VIVS_MMUv2_EXCEPTION_ADDR(i);
> else

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