drm/xe: Fix and re-enable xe_print_blob_ascii85()

Commit 70fb86a85dc9 ("drm/xe: Revert some changes that break a mesa
debug tool") partially reverted some changes to workaround breakage
caused to mesa tools. However, in doing so it also broke fetching the
GuC log via debugfs since xe_print_blob_ascii85() simply bails out.

The fix is to avoid the extra newlines: the devcoredump interface is
line-oriented and adding random newlines in the middle breaks it. If a
tool is able to parse it by looking at the data and checking for chars
that are out of the ascii85 space, it can still do so. A format change
that breaks the line-oriented output on devcoredump however needs better
coordination with existing tools.

v2: Add suffix description comment
v3: Reword explanation of xe_print_blob_ascii85() calling drm_puts()
    in a loop

Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Julia Filipchuk <julia.filipchuk@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: stable@vger.kernel.org
Fixes: 70fb86a85dc9 ("drm/xe: Revert some changes that break a mesa debug tool")
Fixes: ec1455ce7e35 ("drm/xe/devcoredump: Add ASCII85 dump helper function")
Link: https://patchwork.freedesktop.org/patch/msgid/20250123202307.95103-2-jose.souza@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

diff --git a/drivers/gpu/drm/xe/xe_devcoredump.c b/drivers/gpu/drm/xe/xe_devcoredump.c
index a7946a76777e7e757aac9a4d4253605772837183..39fe485d20858f67f3ecfa26cd7347b5c9d41197 100644 (file)
--- a/drivers/gpu/drm/xe/xe_devcoredump.c
+++ b/drivers/gpu/drm/xe/xe_devcoredump.c
@@ -391,42 +391,34 @@ int xe_devcoredump_init(struct xe_device *xe)
 /**
  * xe_print_blob_ascii85 - print a BLOB to some useful location in ASCII85
  *
- * The output is split to multiple lines because some print targets, e.g. dmesg
- * cannot handle arbitrarily long lines. Note also that printing to dmesg in
- * piece-meal fashion is not possible, each separate call to drm_puts() has a
- * line-feed automatically added! Therefore, the entire output line must be
- * constructed in a local buffer first, then printed in one atomic output call.
+ * The output is split into multiple calls to drm_puts() because some print
+ * targets, e.g. dmesg, cannot handle arbitrarily long lines. These targets may
+ * add newlines, as is the case with dmesg: each drm_puts() call creates a
+ * separate line.
  *
  * There is also a scheduler yield call to prevent the 'task has been stuck for
  * 120s' kernel hang check feature from firing when printing to a slow target
  * such as dmesg over a serial port.
  *
- * TODO: Add compression prior to the ASCII85 encoding to shrink huge buffers down.
- *
  * @p: the printer object to output to
  * @prefix: optional prefix to add to output string
+ * @suffix: optional suffix to add at the end. 0 disables it and is
+ *          not added to the output, which is useful when using multiple calls
+ *          to dump data to @p
  * @blob: the Binary Large OBject to dump out
  * @offset: offset in bytes to skip from the front of the BLOB, must be a multiple of sizeof(u32)
  * @size: the size in bytes of the BLOB, must be a multiple of sizeof(u32)
  */
-void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix,
+void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix, char suffix,
                           const void *blob, size_t offset, size_t size)
 {
        const u32 *blob32 = (const u32 *)blob;
        char buff[ASCII85_BUFSZ], *line_buff;
        size_t line_pos = 0;
 
-       /*
-        * Splitting blobs across multiple lines is not compatible with the mesa
-        * debug decoder tool. Note that even dropping the explicit '\n' below
-        * doesn't help because the GuC log is so big some underlying implementation
-        * still splits the lines at 512K characters. So just bail completely for
-        * the moment.
-        */
-       return;
-
 #define DMESG_MAX_LINE_LEN     800
-#define MIN_SPACE              (ASCII85_BUFSZ + 2)             /* 85 + "\n\0" */
+       /* Always leave space for the suffix char and the \0 */
+#define MIN_SPACE              (ASCII85_BUFSZ + 2)     /* 85 + "<suffix>\0" */
 
        if (size & 3)
                drm_printf(p, "Size not word aligned: %zu", size);
@@ -458,7 +450,6 @@ void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix,
                line_pos += strlen(line_buff + line_pos);
 
                if ((line_pos + MIN_SPACE) >= DMESG_MAX_LINE_LEN) {
-                       line_buff[line_pos++] = '\n';
                        line_buff[line_pos++] = 0;
 
                        drm_puts(p, line_buff);
@@ -470,10 +461,11 @@ void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix,
                }
        }
 
+       if (suffix)
+               line_buff[line_pos++] = suffix;
+
        if (line_pos) {
-               line_buff[line_pos++] = '\n';
                line_buff[line_pos++] = 0;
-
                drm_puts(p, line_buff);
        }
 

diff --git a/drivers/gpu/drm/xe/xe_devcoredump.h b/drivers/gpu/drm/xe/xe_devcoredump.h
index 6a17e6d6010220efb8fa97fc7376e68e9d5a658f..5391a80a4d1ba1d0585a67506c607d35609a796d 100644 (file)
--- a/drivers/gpu/drm/xe/xe_devcoredump.h
+++ b/drivers/gpu/drm/xe/xe_devcoredump.h
@@ -29,7 +29,7 @@ static inline int xe_devcoredump_init(struct xe_device *xe)
 }
 #endif
 
-void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix,
+void xe_print_blob_ascii85(struct drm_printer *p, const char *prefix, char suffix,
                           const void *blob, size_t offset, size_t size);
 
 #endif

diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
index 8b65c5e959cc2c84a6e676dede48320344b47278..50c8076b51585219a599bc1f95055b709777ba20 100644 (file)
--- a/drivers/gpu/drm/xe/xe_guc_ct.c
+++ b/drivers/gpu/drm/xe/xe_guc_ct.c
@@ -1724,7 +1724,8 @@ void xe_guc_ct_snapshot_print(struct xe_guc_ct_snapshot *snapshot,
                           snapshot->g2h_outstanding);
 
                if (snapshot->ctb)
-                       xe_print_blob_ascii85(p, "CTB data", snapshot->ctb, 0, snapshot->ctb_size);
+                       xe_print_blob_ascii85(p, "CTB data", '\n',
+                                             snapshot->ctb, 0, snapshot->ctb_size);
        } else {
                drm_puts(p, "CT disabled\n");
        }

diff --git a/drivers/gpu/drm/xe/xe_guc_log.c b/drivers/gpu/drm/xe/xe_guc_log.c
index 80151ff6a71f804b15e9513817f6f3b6a8287bd5..44482ea919924c0a4b0990615a9011d2b2cf26d9 100644 (file)
--- a/drivers/gpu/drm/xe/xe_guc_log.c
+++ b/drivers/gpu/drm/xe/xe_guc_log.c
@@ -207,8 +207,10 @@ void xe_guc_log_snapshot_print(struct xe_guc_log_snapshot *snapshot, struct drm_
        remain = snapshot->size;
        for (i = 0; i < snapshot->num_chunks; i++) {
                size_t size = min(GUC_LOG_CHUNK_SIZE, remain);
+               const char *prefix = i ? NULL : "Log data";
+               char suffix = i == snapshot->num_chunks - 1 ? '\n' : 0;
 
-               xe_print_blob_ascii85(p, i ? NULL : "Log data", snapshot->copy[i], 0, size);
+               xe_print_blob_ascii85(p, prefix, suffix, snapshot->copy[i], 0, size);
                remain -= size;
        }
 }