msm: limits: Add support to handle data greater than PAGE_SIZE

Debug data read was not handling the buffer overflow case when
the data to write is greater than PAGE_SIZE. This resulted in
calling the hardware for new data multiple times.

Returning success when buffer overflowed will cause the sequence
traverse function to call again with a new buffer with increased
size. This process will go on until the buffer size is big enough
to hold the data. But limits data read function couldn't distinguish
if the call is a retry or a new call and will initiate a new data
fetch from hardware and re-populate with new data.

Modify debug read interface to immediately return success when
overflow happens. The debug read function now can distinguish between
a sequence retry call by retaining the data buffer in a static if
overflow happens. When called again, debug read now will avoid
calling the hardware for new data and instead will populate the new
sequence buffer with the previously fetched data.

Change-Id: Icc0eb035047ab734d2eb5366cade4ec187747379
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>

1 files changed, 34 insertions, 13 deletions

diff --git a/drivers/thermal/lmh_interface.c b/drivers/thermal/lmh_interface.c
index ce3854cba1c5..5266a4e64914 100644
--- a/drivers/thermal/lmh_interface.c
+++ b/drivers/thermal/lmh_interface.c
@@ -970,23 +970,44 @@ static ssize_t lmh_dbgfs_config_write(struct file *file,
 
 static int lmh_dbgfs_data_read(struct seq_file *seq_fp, void *data)
 {
-	uint32_t *read_buf = NULL;
-	int ret = 0, i = 0;
-
-	ret = lmh_mon_data->debug_ops->debug_read(lmh_mon_data->debug_ops,
-		&read_buf);
-	if (ret <= 0 || !read_buf)
-		goto dfs_read_exit;
+	static uint32_t *read_buf;
+	static int read_buf_size;
+	int idx = 0, ret = 0, print_ret = 0;
+
+	if (!read_buf_size) {
+		ret = lmh_mon_data->debug_ops->debug_read(
+			lmh_mon_data->debug_ops, &read_buf);
+		if (ret <= 0)
+			goto dfs_read_exit;
+		if (!read_buf || ret < sizeof(uint32_t)) {
+			ret = -EINVAL;
+			goto dfs_read_exit;
+	       }
+		read_buf_size = ret;
+		ret = 0;
+	}
 
 	do {
-		seq_printf(seq_fp, "0x%x ", read_buf[i]);
-		i++;
-		if ((i % LMH_READ_LINE_LENGTH) == 0)
-			seq_puts(seq_fp, "\n");
-	} while (i < (ret / sizeof(uint32_t)));
+		print_ret = seq_printf(seq_fp, "0x%x ", read_buf[idx]);
+		if (print_ret) {
+			pr_err("Seq print error. idx:%d err:%d\n",
+				idx, print_ret);
+			goto dfs_read_exit;
+		}
+		idx++;
+		if ((idx % LMH_READ_LINE_LENGTH) == 0) {
+			print_ret = seq_puts(seq_fp, "\n");
+			if (print_ret) {
+				pr_err("Seq print error. err:%d\n", print_ret);
+				goto dfs_read_exit;
+			}
+		}
+	} while (idx < (read_buf_size / sizeof(uint32_t)));
+	read_buf_size = 0;
+	read_buf = NULL;
 
 dfs_read_exit:
-	return (ret < 0) ? ret : 0;
+	return ret;
 }
 
 static ssize_t lmh_dbgfs_data_write(struct file *file,