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Subject[PATCH V3 1/2] bdisp: Fix a possible sleep-in-atomic bug in bdisp_hw_reset
Date
The driver may sleep under a spinlock.
The function call path is:
bdisp_device_run (acquire the spinlock)
bdisp_hw_reset
msleep --> may sleep

To fix it, readl_poll_timeout_atomic is used to replace msleep.

This bug is found by my static analysis tool(DSAC) and
checked by my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/media/platform/sti/bdisp/bdisp-hw.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/media/platform/sti/bdisp/bdisp-hw.c b/drivers/media/platform/sti/bdisp/bdisp-hw.c
index b7892f3..b63d9c9 100644
--- a/drivers/media/platform/sti/bdisp/bdisp-hw.c
+++ b/drivers/media/platform/sti/bdisp/bdisp-hw.c
@@ -4,7 +4,7 @@
* License terms: GNU General Public License (GPL), version 2
*/

-#include <linux/delay.h>
+#include <linux/iopoll.h>

#include "bdisp.h"
#include "bdisp-filter.h"
@@ -15,7 +15,7 @@

/* Reset & boot poll config */
#define POLL_RST_MAX 50
-#define POLL_RST_DELAY_MS 20
+#define POLL_RST_DELAY_US 20000

enum bdisp_target_plan {
BDISP_RGB,
@@ -366,7 +366,7 @@ struct bdisp_filter_addr {
*/
int bdisp_hw_reset(struct bdisp_dev *bdisp)
{
- unsigned int i;
+ u32 tmp;

dev_dbg(bdisp->dev, "%s\n", __func__);

@@ -378,16 +378,17 @@ int bdisp_hw_reset(struct bdisp_dev *bdisp)
bdisp->regs + BLT_CTL);
writel(0, bdisp->regs + BLT_CTL);

- /* Wait for reset done */
- for (i = 0; i < POLL_RST_MAX; i++) {
- if (readl(bdisp->regs + BLT_STA1) & BLT_STA1_IDLE)
- break;
- msleep(POLL_RST_DELAY_MS);
- }
- if (i == POLL_RST_MAX)
+ /* Wait for reset done.
+ * Despite the large timeout, most of the time the reset happens without
+ * needing any delays */
+ if (readl_poll_timeout_atomic(bdisp->regs + BLT_STA1, tmp,
+ (tmp & BLT_STA1_IDLE), POLL_RST_DELAY_US,
+ POLL_RST_DELAY_US * POLL_RST_MAX)) {
dev_err(bdisp->dev, "Reset timeout\n");
+ return -EAGAIN;
+ }

- return (i == POLL_RST_MAX) ? -EAGAIN : 0;
+ return 0;
}

/**
--
1.7.9.5
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