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pwm: axi-pwmgen: Enable FORCE_ALIGN by default

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Enable the FORCE_ALIGN flag by default in the AXI PWMGEN driver. This
flag makes the behavior of the PWM output consistent with the
description at the top of the driver file.

    * Limitations:
    * - The writes to registers for period and duty are shadowed until
    *   LOAD_CONFIG is written to AXI_PWMGEN_REG_RSTN, at which point
    *   they take effect.
    * - Writing LOAD_CONFIG also has the effect of re-synchronizing all
    *   enabled channels, which could cause glitching on other channels. It
    *   is therefore expected that channels are assigned harmonic periods
    *   and all have a single user coordinating this.

Without this flag, the PWM output does not change until the period of
all PWM output channels has run out, which makes the PWM impossible to
use in some cases because it takes too long to change the output.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20241009-pwm-axi-pwmgen-enable-force_align-v1-2-5d6ad8cbf5b4@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
This commit is contained in:
David Lechner 2024-10-09 16:11:50 -05:00 committed by Uwe Kleine-König
parent 2e82d58c7b
commit 15effedc48
1 changed files with 12 additions and 0 deletions
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12
drivers/pwm/pwm-axi-pwmgen.c
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@ -37,6 +37,8 @@
#define AXI_PWMGEN_REG_RSTN_LOAD_CONFIG BIT(1)
#define AXI_PWMGEN_REG_RSTN_RESET BIT(0)
#define AXI_PWMGEN_REG_NPWM 0x14
#define AXI_PWMGEN_REG_CONFIG 0x18
#define AXI_PWMGEN_REG_CONFIG_FORCE_ALIGN BIT(1)
#define AXI_PWMGEN_CHX_PERIOD(ch) (0x40 + (4 * (ch)))
#define AXI_PWMGEN_CHX_DUTY(ch) (0x80 + (4 * (ch)))
#define AXI_PWMGEN_CHX_OFFSET(ch) (0xC0 + (4 * (ch)))
@ -227,6 +229,16 @@ static int axi_pwmgen_setup(struct regmap *regmap, struct device *dev)
if (ret)
return ret;
/*
* Enable force align so that changes to PWM period and duty cycle take
* effect immediately. Otherwise, the effect of the change is delayed
* until the period of all channels run out, which can be long after the
* apply function returns.
*/
ret = regmap_set_bits(regmap, AXI_PWMGEN_REG_CONFIG, AXI_PWMGEN_REG_CONFIG_FORCE_ALIGN);
if (ret)
return ret;
ret = regmap_read(regmap, AXI_PWMGEN_REG_NPWM, &val);
if (ret)
return ret;