[PATCH] drm/xe/guc: Improve robustness of GuC log dumping to dmesg

[Matthew Brost]

On Tue, Apr 30, 2024 at 04:34:36PM -0700, John.C.Harrison at Intel.com wrote:
> From: John Harrison <John.C.Harrison at Intel.com>
> 
> There is a debug mechanism for dumping the GuC log as an ASCII hex
> stream via dmesg. This is extremely useful for situations where it is
> not possibe to query the log from debugfs (self tests, bugs that cause
> the driver to fail to load, system hangs, etc.). However, dumping via
> dmesg is not the most reliable. The dmesg buffer is limited in size,
> can be rate limited and a simple hex stream is hard to parse by tools.
> 
> So add extra information to the dump to make it more robust and
> parsable. This includes adding start and end tags to delimit the dump,
> using longer lines to reduce the per line overhead, adding a rolling
> count to check for missing lines and interleaved concurrent dumps and
> adding other important information such as the GuC version number and
> timestamp offset.
> 
> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
> ---
>  drivers/gpu/drm/xe/regs/xe_guc_regs.h |  1 +
>  drivers/gpu/drm/xe/xe_guc_log.c       | 78 ++++++++++++++++++++++-----
>  2 files changed, 66 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/regs/xe_guc_regs.h b/drivers/gpu/drm/xe/regs/xe_guc_regs.h
> index 11682e675e0f..45fb3707fabe 100644
> --- a/drivers/gpu/drm/xe/regs/xe_guc_regs.h
> +++ b/drivers/gpu/drm/xe/regs/xe_guc_regs.h
> @@ -82,6 +82,7 @@
>  #define   HUC_LOADING_AGENT_GUC			REG_BIT(1)
>  #define   GUC_WOPCM_OFFSET_VALID		REG_BIT(0)
>  #define GUC_MAX_IDLE_COUNT			XE_REG(0xc3e4)
> +#define GUC_PMTIMESTAMP				XE_REG(0xc3e8)
>  
>  #define GUC_SEND_INTERRUPT			XE_REG(0xc4c8)
>  #define   GUC_SEND_TRIGGER			REG_BIT(0)
> diff --git a/drivers/gpu/drm/xe/xe_guc_log.c b/drivers/gpu/drm/xe/xe_guc_log.c
> index a37ee3419428..ea269efd9c21 100644
> --- a/drivers/gpu/drm/xe/xe_guc_log.c
> +++ b/drivers/gpu/drm/xe/xe_guc_log.c
> @@ -7,10 +7,19 @@
>  
>  #include <drm/drm_managed.h>
>  
> +#include "regs/xe_guc_regs.h"
>  #include "xe_bo.h"
>  #include "xe_gt.h"
>  #include "xe_map.h"
> +#include "xe_mmio.h"
>  #include "xe_module.h"
> +#include "xe_pm.h"
> +
> +static struct xe_guc *
> +log_to_guc(struct xe_guc_log *log)
> +{
> +	return container_of(log, struct xe_guc, log);
> +}
>  
>  static struct xe_gt *
>  log_to_gt(struct xe_guc_log *log)
> @@ -49,32 +58,75 @@ static size_t guc_log_size(void)
>  		CAPTURE_BUFFER_SIZE;
>  }
>  
> +#define BYTES_PER_WORD		sizeof(u32)
> +#define WORDS_PER_DUMP		8
> +#define DUMPS_PER_LINE		4
> +#define LINES_PER_READ		4
> +#define WORDS_PER_READ		(WORDS_PER_DUMP * DUMPS_PER_LINE * LINES_PER_READ)
> +
>  void xe_guc_log_print(struct xe_guc_log *log, struct drm_printer *p)
>  {
> +	static int g_count;
> +	struct xe_uc_fw_version *ver = &log_to_guc(log)->fw.versions.found[XE_UC_FW_VER_RELEASE];
>  	struct xe_device *xe = log_to_xe(log);
>  	size_t size;
> -	int i, j;
> +	char line_buff[DUMPS_PER_LINE * WORDS_PER_DUMP * 9 + 1];
> +	int l_count = g_count++;
> +	int line = 0;
> +	int i, j, k;
> +	u64 ktime;
> +	u32 stamp;
>  
>  	xe_assert(xe, log->bo);
>  
>  	size = log->bo->size;
>  
> -#define DW_PER_READ		128
> -	xe_assert(xe, !(size % (DW_PER_READ * sizeof(u32))));
> -	for (i = 0; i < size / sizeof(u32); i += DW_PER_READ) {
> -		u32 read[DW_PER_READ];
> +	drm_printf(p, "[Capture/%d.%d] Dumping GuC log for %ps...\n",
> +		   l_count, line++, __builtin_return_address(0));
> +
> +	drm_printf(p, "[Capture/%d.%d] GuC version %u.%u.%u\n",
> +		   l_count, line++, ver->major, ver->minor, ver->patch);
> +
> +	ktime = ktime_get_boottime_ns();
> +	drm_printf(p, "[Capture/%d.%d] Kernel timestamp: 0x%08llX [%llu]\n",
> +		   l_count, line++, ktime, ktime);
>  
> -		xe_map_memcpy_from(xe, read, &log->bo->vmap, i * sizeof(u32),
> -				   DW_PER_READ * sizeof(u32));
> -#define DW_PER_PRINT		4
> -		for (j = 0; j < DW_PER_READ / DW_PER_PRINT; ++j) {
> -			u32 *print = read + j * DW_PER_PRINT;
> +	xe_pm_runtime_get(xe);
> +	stamp = xe_mmio_read32(log_to_gt(log), GUC_PMTIMESTAMP);
> +	xe_pm_runtime_put(xe);

Just a quick drive by comment, fine grained PM control like this frowned
upon in Xe or maybe even not allowed. Rodrigo / Matt Auld would would be
the experts here.

Presumbly all the callers should already have a PM ref.

> +	drm_printf(p, "[Capture/%d.%d] GuC timestamp: 0x%08X [%u]\n",
> +		   l_count, line++, stamp, stamp);
>  
> -			drm_printf(p, "0x%08x 0x%08x 0x%08x 0x%08x\n",
> -				   *(print + 0), *(print + 1),
> -				   *(print + 2), *(print + 3));
> +	drm_printf(p, "[Capture/%d.%d] CS timestamp frequency: %u Hz\n",
> +		   l_count, line++, log_to_gt(log)->info.reference_clock);
> +
> +	xe_assert(xe, !(size % (WORDS_PER_READ * BYTES_PER_WORD)));
> +	for (i = 0; i < size / BYTES_PER_WORD; i += WORDS_PER_READ) {
> +		u32 read[WORDS_PER_READ];
> +
> +		xe_map_memcpy_from(xe, read, &log->bo->vmap, i * BYTES_PER_WORD,
> +				   WORDS_PER_READ * BYTES_PER_WORD);
> +

Also I think the above pukes without a PM ref too.

Matt

> +		for (j = 0; j < WORDS_PER_READ; ) {
> +			u32 done = 0;
> +
> +			for (k = 0; k < DUMPS_PER_LINE; k++) {
> +				line_buff[done++] = ' ';
> +				done += hex_dump_to_buffer(read + j,
> +							   sizeof(*read) * (WORDS_PER_READ - j),
> +							   WORDS_PER_DUMP * BYTES_PER_WORD,
> +							   BYTES_PER_WORD,
> +							   line_buff + done,
> +							   sizeof(line_buff) - done,
> +							   false);
> +				j += WORDS_PER_DUMP;
> +			}
> +
> +			drm_printf(p, "[Capture/%d.%d]%s\n", l_count, line++, line_buff);
>  		}
>  	}
> +
> +	drm_printf(p, "[Capture/%d.%d] Done.\n", l_count, line++);
>  }
>  
>  int xe_guc_log_init(struct xe_guc_log *log)
> -- 
> 2.43.2
>