msm: mdss: handle synchronization issues during DSI debugfs read/write

Handle race condition during read/write operations to DSI debugfs nodes
related to DSI panel ON/OFF commands.

Change-Id: I29c4ad74bf21d4cb5362565e902a682fe7263147
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>
Signed-off-by: Rajkumar Subbiah <rsubbia@codeaurora.org>

diff --git a/drivers/video/fbdev/msm/mdss_dsi.c b/drivers/video/fbdev/msm/mdss_dsi.c
index 51745a9..a79cd1f 100644 (file)
--- a/drivers/video/fbdev/msm/mdss_dsi.c
+++ b/drivers/video/fbdev/msm/mdss_dsi.c
@@ -629,6 +629,7 @@ struct buf_data {
        char *string_buf; /* cmd buf as string, 3 bytes per number */
        int sblen; /* string buffer length */
        int sync_flag;
+       struct mutex dbg_mutex; /* mutex to synchronize read/write/flush */
 };
 
 struct mdss_dsi_debugfs_info {
@@ -718,6 +719,7 @@ static ssize_t mdss_dsi_cmd_read(struct file *file, char __user *buf,
        char *bp;
        ssize_t ret = 0;
 
+       mutex_lock(&pcmds->dbg_mutex);
        if (*ppos == 0) {
                kfree(pcmds->string_buf);
                pcmds->string_buf = NULL;
@@ -736,6 +738,7 @@ static ssize_t mdss_dsi_cmd_read(struct file *file, char __user *buf,
                buffer = kmalloc(bsize, GFP_KERNEL);
                if (!buffer) {
                        pr_err("%s: Failed to allocate memory\n", __func__);
+                       mutex_unlock(&pcmds->dbg_mutex);
                        return -ENOMEM;
                }
 
@@ -771,10 +774,12 @@ static ssize_t mdss_dsi_cmd_read(struct file *file, char __user *buf,
                kfree(pcmds->string_buf);
                pcmds->string_buf = NULL;
                pcmds->sblen = 0;
+               mutex_unlock(&pcmds->dbg_mutex);
                return 0; /* the end */
        }
        ret = simple_read_from_buffer(buf, count, ppos, pcmds->string_buf,
                                      pcmds->sblen);
+       mutex_unlock(&pcmds->dbg_mutex);
        return ret;
 }
 
@@ -786,6 +791,7 @@ static ssize_t mdss_dsi_cmd_write(struct file *file, const char __user *p,
        int blen = 0;
        char *string_buf;
 
+       mutex_lock(&pcmds->dbg_mutex);
        if (*ppos == 0) {
                kfree(pcmds->string_buf);
                pcmds->string_buf = NULL;
@@ -797,6 +803,7 @@ static ssize_t mdss_dsi_cmd_write(struct file *file, const char __user *p,
        string_buf = krealloc(pcmds->string_buf, blen + 1, GFP_KERNEL);
        if (!string_buf) {
                pr_err("%s: Failed to allocate memory\n", __func__);
+               mutex_unlock(&pcmds->dbg_mutex);
                return -ENOMEM;
        }
 
@@ -806,6 +813,7 @@ static ssize_t mdss_dsi_cmd_write(struct file *file, const char __user *p,
        string_buf[blen] = '\0';
        pcmds->string_buf = string_buf;
        pcmds->sblen = blen;
+       mutex_unlock(&pcmds->dbg_mutex);
        return ret;
 }
 
@@ -816,8 +824,12 @@ static int mdss_dsi_cmd_flush(struct file *file, fl_owner_t id)
        char *buf, *bufp, *bp;
        struct dsi_ctrl_hdr *dchdr;
 
-       if (!pcmds->string_buf)
+       mutex_lock(&pcmds->dbg_mutex);
+
+       if (!pcmds->string_buf) {
+               mutex_unlock(&pcmds->dbg_mutex);
                return 0;
+       }
 
        /*
         * Allocate memory for command buffer
@@ -830,6 +842,7 @@ static int mdss_dsi_cmd_flush(struct file *file, fl_owner_t id)
                kfree(pcmds->string_buf);
                pcmds->string_buf = NULL;
                pcmds->sblen = 0;
+               mutex_unlock(&pcmds->dbg_mutex);
                return -ENOMEM;
        }
 
@@ -854,6 +867,7 @@ static int mdss_dsi_cmd_flush(struct file *file, fl_owner_t id)
                        pr_err("%s: dtsi cmd=%x error, len=%d\n",
                                __func__, dchdr->dtype, dchdr->dlen);
                        kfree(buf);
+                       mutex_unlock(&pcmds->dbg_mutex);
                        return -EINVAL;
                }
                bp += sizeof(*dchdr);
@@ -865,6 +879,7 @@ static int mdss_dsi_cmd_flush(struct file *file, fl_owner_t id)
                pr_err("%s: dcs_cmd=%x len=%d error!\n", __func__,
                                bp[0], len);
                kfree(buf);
+               mutex_unlock(&pcmds->dbg_mutex);
                return -EINVAL;
        }
 
@@ -877,6 +892,7 @@ static int mdss_dsi_cmd_flush(struct file *file, fl_owner_t id)
                pcmds->buf = buf;
                pcmds->blen = blen;
        }
+       mutex_unlock(&pcmds->dbg_mutex);
        return 0;
 }
 
@@ -891,6 +907,7 @@ struct dentry *dsi_debugfs_create_dcs_cmd(const char *name, umode_t mode,
                                struct dentry *parent, struct buf_data *cmd,
                                struct dsi_panel_cmds ctrl_cmds)
 {
+       mutex_init(&cmd->dbg_mutex);
        cmd->buf = ctrl_cmds.buf;
        cmd->blen = ctrl_cmds.blen;
        cmd->string_buf = NULL;