drm/amdgpu: Optimize EEPROM RAS table I/O

Split functionality between read and write, which
simplifies the code and exposes areas of
optimization and more or less complexity, and take
advantage of that.

Read and write the table in one go; use a separate
stage to decode or encode the data, as opposed to
on the fly, which keeps the I2C bus busy. Use a
single read/write to read/write the table or at
most two if the number of records we're
reading/writing wraps around.

Check the check-sum of a table in EEPROM on init.

Update the checksum at the same time as when
updating the table header signature, when the
threshold was increased on boot.

Take advantage of arithmetic modulo 256, that is,
use a byte!, to greatly simplify checksum
arithmetic.

Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.c

@@ -176,7 +176,7 @@ static int __amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr,
  *
  * Returns the number of bytes read/written; -errno on error.
  */
-int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr,
+static int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr,
 			      u8 *eeprom_buf, u16 buf_size, bool read)
 {
 	const struct i2c_adapter_quirks *quirks = i2c_adap->quirks;
@@ -221,3 +221,19 @@ int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr,
 		return res;
 	}
 }
+
+int amdgpu_eeprom_read(struct i2c_adapter *i2c_adap,
+		       u32 eeprom_addr, u8 *eeprom_buf,
+		       u16 bytes)
+{
+	return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes,
+				  true);
+}
+
+int amdgpu_eeprom_write(struct i2c_adapter *i2c_adap,
+			u32 eeprom_addr, u8 *eeprom_buf,
+			u16 bytes)
+{
+	return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes,
+				  false);
+}

drivers/gpu/drm/amd/amdgpu/amdgpu_eeprom.h

@@ -26,23 +26,12 @@
 
 #include <linux/i2c.h>
 
-int amdgpu_eeprom_xfer(struct i2c_adapter *i2c_adap, u32 eeprom_addr,
-		       u8 *eeprom_buf, u16 bytes, bool read);
-
-static inline int amdgpu_eeprom_read(struct i2c_adapter *i2c_adap,
+int amdgpu_eeprom_read(struct i2c_adapter *i2c_adap,
 		       u32 eeprom_addr, u8 *eeprom_buf,
-				     u16 bytes)
-{
-	return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes,
-				  true);
-}
+		       u16 bytes);
 
-static inline int amdgpu_eeprom_write(struct i2c_adapter *i2c_adap,
+int amdgpu_eeprom_write(struct i2c_adapter *i2c_adap,
 			u32 eeprom_addr, u8 *eeprom_buf,
-				      u16 bytes)
-{
-	return amdgpu_eeprom_xfer(i2c_adap, eeprom_addr, eeprom_buf, bytes,
-				  false);
-}
+			u16 bytes);
 
 #endif

drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c

@@ -451,7 +451,7 @@ static ssize_t amdgpu_ras_debugfs_eeprom_write(struct file *f,
 	ret = amdgpu_ras_eeprom_reset_table(
 		&(amdgpu_ras_get_context(adev)->eeprom_control));
 
-	if (ret > 0) {
+	if (!ret) {
 		/* Something was written to EEPROM.
 		 */
 		amdgpu_ras_get_context(adev)->flags = RAS_DEFAULT_FLAGS;
@@ -1821,7 +1821,7 @@ int amdgpu_ras_save_bad_pages(struct amdgpu_device *adev)
 	save_count = data->count - control->ras_num_recs;
 	/* only new entries are saved */
 	if (save_count > 0) {
-		if (amdgpu_ras_eeprom_write(control,
+		if (amdgpu_ras_eeprom_append(control,
 					     &data->bps[control->ras_num_recs],
 					     save_count)) {
 			dev_err(adev->dev, "Failed to save EEPROM table data!");

drivers/gpu/drm/amd/amdgpu/amdgpu_ras_eeprom.h

@@ -28,7 +28,7 @@
 
 struct amdgpu_device;
 
-enum amdgpu_ras_eeprom_err_type{
+enum amdgpu_ras_eeprom_err_type {
 	AMDGPU_RAS_EEPROM_ERR_PLACE_HOLDER,
 	AMDGPU_RAS_EEPROM_ERR_RECOVERABLE,
 	AMDGPU_RAS_EEPROM_ERR_NON_RECOVERABLE
@@ -51,17 +51,34 @@ struct amdgpu_ras_eeprom_control {
 	 */
 	u32 i2c_address;
 
-	uint32_t next_addr;
+	/* The byte offset off of @i2c_address
+	 * where the table header is found,
+	 * and where the records start--always
+	 * right after the header.
+	 */
+	u32 ras_header_offset;
+	u32 ras_record_offset;
 
 	/* Number of records in the table.
 	 */
-	unsigned int ras_num_recs;
+	u32 ras_num_recs;
+
+	/* First record index to read, 0-based.
+	 * Range is [0, num_recs-1]. This is
+	 * an absolute index, starting right after
+	 * the table header.
+	 */
+	u32 ras_fri;
+
+	/* Maximum possible number of records
+	 * we could store, i.e. the maximum capacity
+	 * of the table.
+	 */
+	u32 ras_max_record_count;
 
 	/* Protect table access via this mutex.
 	 */
 	struct mutex ras_tbl_mutex;
-
-	u8 tbl_byte_sum;
 };
 
 /*
@@ -91,6 +108,7 @@ struct eeprom_table_record {
 
 int amdgpu_ras_eeprom_init(struct amdgpu_ras_eeprom_control *control,
 			   bool *exceed_err_limit);
+
 int amdgpu_ras_eeprom_reset_table(struct amdgpu_ras_eeprom_control *control);
 
 bool amdgpu_ras_eeprom_check_err_threshold(struct amdgpu_device *adev);
@@ -98,7 +116,7 @@ bool amdgpu_ras_eeprom_check_err_threshold(struct amdgpu_device *adev);
 int amdgpu_ras_eeprom_read(struct amdgpu_ras_eeprom_control *control,
 			   struct eeprom_table_record *records, const u32 num);
 
-int amdgpu_ras_eeprom_write(struct amdgpu_ras_eeprom_control *control,
+int amdgpu_ras_eeprom_append(struct amdgpu_ras_eeprom_control *control,
 			     struct eeprom_table_record *records, const u32 num);
 
 inline uint32_t amdgpu_ras_eeprom_max_record_count(void);