debugfs: a tool to print 32-bit registers

This is V2 of what I posted a few days ago. I also updates the file in Documentation. I Cc:d people who gave feedback.

Patch 2 uses the new tool for an existing file I didn't initially notice (I had a victim file, but it's seriously failing compilation). Code removal there is almost zero because Felipe Balbi already did stuff in the way I do.

Mark Brown suggested to look at drivers/base/regmap, and actually this may be duplicating what is already being worked on in a more general way. My code base is earlier than regmap so I didn't notice. Unfortunately I have no resources left to study regmap as it deserves.

Mark, if you say this is not useful at this point, I'm fine with it; I may return with some regbase-aware code when time permits if it's not already there.

/alessandro

Alessandro Rubini (2):
debugfs: add tools to printk 32-bit registers
usb: dwc3: use debugfs_print_regs32()

 Documentation/filesystems/debugfs.txt |   32 +++++++++++-
 drivers/usb/dwc3/debugfs.c            |   15 +----
 fs/debugfs/file.c                     |   90 +++++++++++++++++++++++++++++++++
 include/linux/debugfs.h               |   26 +++++++++
 4 files changed, 150 insertions(+), 13 deletions(-)

-ENOPATCH ?? I didn't receive any replies to this mail with the patch. Is my mailer screwed up ?

balbi

You are right. Thanks and apologies. I mistyped Giancarlo Asnaghi's alias in all three, and the sending was interrupted. I resent now.

thanks
/alessandro

Some debugfs file I deal with are mostly blocks of registers, i.e. lines of the form "<name> = 0x<value>". Some files are only registers, some include registers blocks among other material. This patch introduces data structures and functions to deal with both cases. I expect more users of this over time.

---
 Documentation/filesystems/debugfs.txt |   32 +++++++++++-
 fs/debugfs/file.c                     |   90 +++++++++++++++++++++++++++++++++
 include/linux/debugfs.h               |   26 +++++++++
 3 files changed, 147 insertions(+), 1 deletions(-)

index 742cc06..f04066a 100644
@@ -97,7 +97,8 @@ A read on the resulting file will yield either Y (for non-zero values) or
 N, followed by a newline.  If written to, it will accept either upper- or
 lower-case values, or 1 or 0.  Any other input will be silently ignored.
 
-Finally, a block of arbitrary binary data can be exported with:
+Another option is exporting a block of arbitrary binary data, with
+this structure and function:
 
     struct debugfs_blob_wrapper {
 	void *data;

@@ -115,6 +116,35 @@ can be used to export binary information, but there does not appear to be
 any code which does so in the mainline.  Note that all files created with
 debugfs_create_blob() are read-only.
 
+If you want to dump a block of registers (something that happens quite
+often during development, even if little such code reaches mainline.
+Debugfs offers two functions: one to make a registers-only file, and
+another to insert a register block in the middle of another sequential
+file.
+
+    struct debugfs_reg32 {
+	char *name;
+	unsigned long offset;
+    };
+
+    struct debugfs_regset32 {
+	struct debugfs_reg32 *regs;
+	int nregs;
+	void __iomem *base;
+    };
+
+    struct dentry *debugfs_create_regset32(const char *name, mode_t mode,
+				     struct dentry *parent,
+				     struct debugfs_regset32 *regset);
+
+    int debugfs_print_regs32(struct seq_file *s, struct debugfs_reg32 *regs,
+			 int nregs, void __iomem *base, char *prefix);
+
+The "base" argument may be 0, but you may want to build the reg32 array
+using __stringify, and a number of register names (macros) are actually
+byte offsets over a base for the register block.
+
+
 There are a couple of other directory-oriented helper functions:
 
     struct dentry *debugfs_rename(struct dentry *old_dir, 

index e7d9b20..5e6b01f 100644
@@ -16,6 +16,7 @@
 #define _DEBUGFS_H_
 
 #include <linux/fs.h>
+#include <linux/seq_file.h>
 
 #include <linux/types.h>
 

@@ -26,6 +27,17 @@ struct debugfs_blob_wrapper {
 	unsigned long size;
 };
 
+struct debugfs_reg32 {
+	char *name;
+	unsigned long offset;
+};
+
+struct debugfs_regset32 {
+	struct debugfs_reg32 *regs;
+	int nregs;
+	void __iomem *base;
+};
+
 extern struct dentry *arch_debugfs_dir;
 
 #if defined(CONFIG_DEBUG_FS)

@@ -74,6 +86,13 @@ struct dentry *debugfs_create_blob(const char *name, mode_t mode,
 				  struct dentry *parent,
 				  struct debugfs_blob_wrapper *blob);
 
+struct dentry *debugfs_create_regset32(const char *name, mode_t mode,
+				     struct dentry *parent,
+				     struct debugfs_regset32 *regset);
+
+int debugfs_print_regs32(struct seq_file *s, struct debugfs_reg32 *regs,
+			 int nregs, void __iomem *base, char *prefix);
+
 bool debugfs_initialized(void);
 
 #else

@@ -188,6 +207,13 @@ static inline struct dentry *debugfs_create_blob(const char *name, mode_t mode,
 	return ERR_PTR(-ENODEV);
 }
 
+static inline struct dentry *debugfs_create_regset32(const char *name,
+				   mode_t mode, struct dentry *parent,
+				   struct debugfs_regset32 *regset)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline bool debugfs_initialized(void)
 {
 	return false;

1.6.0.2

This a use example of the regs32 utilities in debugfs, although this fuse use ":" as separator between name and value, and debugs uses "=" (as it looked to me a more common practice).

---
 drivers/usb/dwc3/debugfs.c |   15 +++------------
 1 files changed, 3 insertions(+), 12 deletions(-)

index da1ad77..d9e7a26 100644
@@ -51,18 +51,13 @@
 #include "gadget.h"
 #include "io.h"
 
-struct dwc3_register {
-	const char	*name;
-	u32		offset;
-};
-
 #define dump_register(nm)				\
 {							\
 	.name	= __stringify(nm),			\
 	.offset	= DWC3_ ##nm,				\
 }
 
-static const struct dwc3_register dwc3_regs[] = {
+static const struct debugfs_reg32 dwc3_regs[] = {
 	dump_register(GSBUSCFG0),
 	dump_register(GSBUSCFG1),
 	dump_register(GTXTHRCFG),

@@ -385,12 +380,8 @@ static int dwc3_regdump_show(struct seq_file *s, void *unused)
 	int			i;
 
 	seq_printf(s, "DesignWare USB3 Core Register Dump\n");
-
-	for (i = 0; i < ARRAY_SIZE(dwc3_regs); i++) {
-		seq_printf(s, "%-20s :    %08x\n", dwc3_regs[i].name,
-				dwc3_readl(dwc->regs, dwc3_regs[i].offset));
-	}
-
+	debugfs_print_regs32(s, dwc3_regs, ARRAY_SIZE(dwc3_regs),
+			     dwc->regs, "");
 	return 0;
 }
 

1.6.0.2

Felipe, any objection to me applying this patch?

thanks,

greg k-h

none whatsoever:

balbi

I've applied this, but it causes the following complier warnings to be spit out:

drivers/usb/dwc3/debugfs.c: In function ‘dwc3_regdump_show’:
drivers/usb/dwc3/debugfs.c:384:9: warning: passing argument 2 of ‘debugfs_print_regs32’ discards ‘const’ qualifier from pointer target type [enabled by default] include/linux/debugfs.h:93:5: note: expected ‘struct debugfs_reg32 *’ but argument is of type ‘const struct debugfs_reg32 *’ drivers/usb/dwc3/debugfs.c:380:8: warning: unused variable ‘i’ [-Wunused-variable]

Alessandro, care to send me a follow-on patch to fix this up?

thanks,

greg k-h

The previous patch left an unused variable, I apologize.

---
 drivers/usb/dwc3/debugfs.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

index d9e7a26..fcfa915 100644
@@ -377,7 +377,6 @@ static const struct debugfs_reg32 dwc3_regs[] = {
 static int dwc3_regdump_show(struct seq_file *s, void *unused)
 {
 	struct dwc3		*dwc = s->private;
-	int			i;
 
 	seq_printf(s, "DesignWare USB3 Core Register Dump\n");
 	debugfs_print_regs32(s, dwc3_regs, ARRAY_SIZE(dwc3_regs),

1.5.6.5

---
 fs/debugfs/file.c       |    2 +-
 include/linux/debugfs.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

index f31a27c..fc98ec9 100644
@@ -548,7 +548,7 @@ EXPORT_SYMBOL_GPL(debugfs_create_blob);
  * because some peripherals have several blocks of identical registers,
  * for example configuration of dma channels
  */
-int debugfs_print_regs32(struct seq_file *s, struct debugfs_reg32 *regs,
+int debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs,
 			   int nregs, void __iomem *base, char *prefix)
 {
 	int i, ret = 0;

index 5e6b01f..e8c3abc 100644
@@ -90,7 +90,7 @@ struct dentry *debugfs_create_regset32(const char *name, mode_t mode,
 				     struct dentry *parent,
 				     struct debugfs_regset32 *regset);
 
-int debugfs_print_regs32(struct seq_file *s, struct debugfs_reg32 *regs,
+int debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs,
 			 int nregs, void __iomem *base, char *prefix);
 
 bool debugfs_initialized(void);

1.5.6.5

We definitely can't just use this directly with regmap as regmap is for non memory mapped devices and makes some assumptions in that regard. I was mostly just suggesting that we try to keep the file formats similar to make life easier for userspace.