From: Uwe Kleine-König u.kleine-koenig@pengutronix.de
stable inclusion from stable-5.10.69 commit 777344da345a374eb74f2a743b5399e6e60d566b bugzilla: 182675 https://gitee.com/openeuler/kernel/issues/I4I3ED
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 020162d6f49f2963062229814a56a89c86cbeaa8 upstream.
This fixes a race condition: After pwmchip_add() is called there might already be a consumer and then modifying the hardware behind the consumer's back is bad. So reset before calling pwmchip_add().
Note that reseting the hardware isn't the right thing to do if the PWM is already running as it might e.g. disable (or even enable) a backlight that is supposed to be on (or off).
Fixes: 4dce82c1e840 ("pwm: add pwm-mxs support") Cc: Sascha Hauer s.hauer@pengutronix.de Cc: Shawn Guo shawnguo@kernel.org Signed-off-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Thierry Reding thierry.reding@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- drivers/pwm/pwm-mxs.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c index 7ce616923c52..41bdbe71ae46 100644 --- a/drivers/pwm/pwm-mxs.c +++ b/drivers/pwm/pwm-mxs.c @@ -148,6 +148,11 @@ static int mxs_pwm_probe(struct platform_device *pdev) return ret; }
+ /* FIXME: Only do this if the PWM isn't already running */ + ret = stmp_reset_block(mxs->base); + if (ret) + return dev_err_probe(&pdev->dev, ret, "failed to reset PWM\n"); + ret = pwmchip_add(&mxs->chip); if (ret < 0) { dev_err(&pdev->dev, "failed to add pwm chip %d\n", ret); @@ -156,15 +161,7 @@ static int mxs_pwm_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, mxs);
- ret = stmp_reset_block(mxs->base); - if (ret) - goto pwm_remove; - return 0; - -pwm_remove: - pwmchip_remove(&mxs->chip); - return ret; }
static int mxs_pwm_remove(struct platform_device *pdev)