5.4-stable review patch. If anyone has any objections, please let me know.
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From: Laurentiu Mihalcea laurentiu.mihalcea@nxp.com
commit 65c6f742ab14ab1a2679fba72b82dcc0289d96f1 upstream.
As per the i.MX93 TRM, section 67.3.2.1 "MOD register update", the value of the TPM counter does NOT get updated when writing MOD.MOD unless SC.CMOD != 0. Therefore, with the current code, assuming the following sequence:
1) pwm_disable() 2) pwm_apply_might_sleep() /* period is changed here */ 3) pwm_enable()
and assuming only one channel is active, if CNT.COUNT is higher than the MOD.MOD value written during the pwm_apply_might_sleep() call then, when re-enabling the PWM during pwm_enable(), the counter will end up resetting after UINT32_MAX - CNT.COUNT + MOD.MOD cycles instead of MOD.MOD cycles as normally expected.
Fix this problem by forcing a reset of the TPM counter before MOD.MOD is written.
Fixes: 738a1cfec2ed ("pwm: Add i.MX TPM PWM driver support") Cc: stable@vger.kernel.org Signed-off-by: Laurentiu Mihalcea laurentiu.mihalcea@nxp.com Link: https://lore.kernel.org/r/20250728194144.22884-1-laurentiumihalcea111@gmail.... Signed-off-by: Uwe Kleine-König ukleinek@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pwm/pwm-imx-tpm.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/drivers/pwm/pwm-imx-tpm.c +++ b/drivers/pwm/pwm-imx-tpm.c @@ -205,6 +205,15 @@ static int pwm_imx_tpm_apply_hw(struct p writel(val, tpm->base + PWM_IMX_TPM_SC);
/* + * if the counter is disabled (CMOD == 0), programming the new + * period length (MOD) will not reset the counter (CNT). If + * CNT.COUNT happens to be bigger than the new MOD value then + * the counter will end up being reset way too late. Therefore, + * manually reset it to 0. + */ + if (!cmod) + writel(0x0, tpm->base + PWM_IMX_TPM_CNT); + /* * set period count: * if the PWM is disabled (CMOD[1:0] = 2b00), then MOD register * is updated when MOD register is written.