[PATCH v7 0/4] Microchip soft ip corePWM driver

[PATCH v7 0/4] Microchip soft ip corePWM driver

[Conor Dooley]

From: Conor Dooley <conor.dooley@microchip.com>

Hey Uwe, all,

(~same cover as v5)

Added some extra patches so I have a cover letter this time.
You pointed out that I was overriding npwmcells in the driver and I
realised that the dt & binding were not correct so I have added two
simple patches to deal with that. The dts patch I will take in my tree
once the binding is applied.

For the maintainers entry, I mentioned before that I have several
changes in-flight for it. We are late~(ish)~ in the cycle so I doubt
you'll be applying this for v5.20, but in the off chance you do - I
would be happy to send it (with your Ack) alongside an i2c addition
that is "deferred". I rebased it ~today~ on top of an additional change
so it may not apply for you.

In your review of v3, you had a lot of comments about the period and
duty cycle calculations, so I have had another run at them. I converted
the period calculation to "search" from the bottom up for the suitable
prescale value. The duty cycle calculation has been fixed - the problem
was exactly what I suspected in my replies to your review. I had to block
the use of a 0xFF period_steps register value (which I think should be
covered by the updated comment and limitation #2).

Beyond that, I have rebased on -next and converted to the devm_ stuff
in probe that was recently added & dropped remove() - as requested.
I added locking to protect the period racing, changed the #defines and
switched to returning -EINVAL when the period is locked to a value
greater than that requested.

I'll take the dts change myself once the rest is merged.

Thanks,
Conor.

Changes from v6:
- Dropped an unused variable that I'd missed
- Actually check the return values of the mutex lock()s
- Re-rebased on -next for the MAINTAINERS patch (again...)

Changes from v5:
- switched to a mutex b/c we must sleep with the lock taken
- simplified the locking in apply() and added locking to get_state()
- reworked apply() as requested
- removed the loop in the period calculation (thanks Uwe!)
- add a copy of the enable registers in the driver to save on reads.
- remove the second (useless) write to sync_update
- added some missing rounding in get_state()
- couple other minor cleanups as requested in:
https://lore.kernel.org/linux-riscv/20220709160206.cw5luo7kxdshoiua@pengutronix.de/

Changes from v4:
- dropped some accidentally added files

Conor Dooley (4):
  dt-bindings: pwm: fix microchip corePWM's pwm-cells
  riscv: dts: fix the icicle's #pwm-cells
  pwm: add microchip soft ip corePWM driver
  MAINTAINERS: add pwm to PolarFire SoC entry

 .../bindings/pwm/microchip,corepwm.yaml       |   4 +-
 MAINTAINERS                                   |   1 +
 .../dts/microchip/mpfs-icicle-kit-fabric.dtsi |   2 +-
 drivers/pwm/Kconfig                           |  10 +
 drivers/pwm/Makefile                          |   1 +
 drivers/pwm/pwm-microchip-core.c              | 371 ++++++++++++++++++
 6 files changed, 387 insertions(+), 2 deletions(-)
 create mode 100644 drivers/pwm/pwm-microchip-core.c


base-commit: a3fd3ca134d9485a0f9a7bdcffd7f8bae27f79d3
-- 
2.37.1

[PATCH v7 1/4] dt-bindings: pwm: fix microchip corePWM's pwm-cells

[Conor Dooley]

From: Conor Dooley <conor.dooley@microchip.com>

corePWM is capable of inverted operation but the binding requires
\#pwm-cells of 2. Expand the binding to support setting the polarity.

Fixes: df77f7735786 ("dt-bindings: pwm: add microchip corepwm binding")
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml b/Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml
index a7fae1772a81..cd8e9a8907f8 100644
--- a/Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml
+++ b/Documentation/devicetree/bindings/pwm/microchip,corepwm.yaml
@@ -30,7 +30,9 @@ properties:
     maxItems: 1
 
   "#pwm-cells":
-    const: 2
+    enum: [2, 3]
+    description:
+      The only flag supported by the controller is PWM_POLARITY_INVERTED.
 
   microchip,sync-update-mask:
     description: |
-- 
2.37.1

Re: [PATCH v7 1/4] dt-bindings: pwm: fix microchip corePWM's pwm-cells

[Uwe Kleine-König]

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On Thu, Jul 21, 2022 at 06:21:07PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> corePWM is capable of inverted operation but the binding requires
> \#pwm-cells of 2. Expand the binding to support setting the polarity.
> 
> Fixes: df77f7735786 ("dt-bindings: pwm: add microchip corepwm binding")
> Acked-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

I'm surprised by myself I didn't notice this when acking df77f7735786,
*shrug*.

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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[PATCH v7 2/4] riscv: dts: fix the icicle's #pwm-cells

[Conor Dooley]

From: Conor Dooley <conor.dooley@microchip.com>

\#pwm-cells for the Icicle kit's fabric PWM was incorrectly set to 2 &
blindly overridden by the (out of tree) driver anyway. The core can
support inverted operation, so update the entry to correctly report its
capabilities.

Fixes: 72560c6559b8 ("riscv: dts: microchip: add fpga fabric section to icicle kit")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi b/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi
index 0d28858b83f2..e09a13aef268 100644
--- a/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi
+++ b/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi
@@ -8,7 +8,7 @@ core_pwm0: pwm@41000000 {
 		compatible = "microchip,corepwm-rtl-v4";
 		reg = <0x0 0x41000000 0x0 0xF0>;
 		microchip,sync-update-mask = /bits/ 32 <0>;
-		#pwm-cells = <2>;
+		#pwm-cells = <3>;
 		clocks = <&fabric_clk3>;
 		status = "disabled";
 	};
-- 
2.37.1

Re: [PATCH v7 2/4] riscv: dts: fix the icicle's #pwm-cells

[Uwe Kleine-König]

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On Thu, Jul 21, 2022 at 06:21:08PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> \#pwm-cells for the Icicle kit's fabric PWM was incorrectly set to 2 &
> blindly overridden by the (out of tree) driver anyway. The core can
> support inverted operation, so update the entry to correctly report its
> capabilities.
> 
> Fixes: 72560c6559b8 ("riscv: dts: microchip: add fpga fabric section to icicle kit")
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi b/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi
> index 0d28858b83f2..e09a13aef268 100644
> --- a/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi
> +++ b/arch/riscv/boot/dts/microchip/mpfs-icicle-kit-fabric.dtsi
> @@ -8,7 +8,7 @@ core_pwm0: pwm@41000000 {
>  		compatible = "microchip,corepwm-rtl-v4";
>  		reg = <0x0 0x41000000 0x0 0xF0>;
>  		microchip,sync-update-mask = /bits/ 32 <0>;
> -		#pwm-cells = <2>;
> +		#pwm-cells = <3>;
>  		clocks = <&fabric_clk3>;
>  		status = "disabled";
>  	};

I checked there are no consumers that need adaption, so:

Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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[PATCH v7 3/4] pwm: add microchip soft ip corePWM driver

[Conor Dooley]

From: Conor Dooley <conor.dooley@microchip.com>

Add a driver that supports the Microchip FPGA "soft" PWM IP core.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 drivers/pwm/Kconfig              |  10 +
 drivers/pwm/Makefile             |   1 +
 drivers/pwm/pwm-microchip-core.c | 371 +++++++++++++++++++++++++++++++
 3 files changed, 382 insertions(+)
 create mode 100644 drivers/pwm/pwm-microchip-core.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 904de8d61828..007ea5750e73 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -383,6 +383,16 @@ config PWM_MEDIATEK
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-mediatek.
 
+config PWM_MICROCHIP_CORE
+	tristate "Microchip corePWM PWM support"
+	depends on SOC_MICROCHIP_POLARFIRE || COMPILE_TEST
+	depends on HAS_IOMEM && OF
+	help
+	  PWM driver for Microchip FPGA soft IP core.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-microchip-core.
+
 config PWM_MXS
 	tristate "Freescale MXS PWM support"
 	depends on ARCH_MXS || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 5c08bdb817b4..43feb7cfc66a 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_PWM_LPSS_PCI)	+= pwm-lpss-pci.o
 obj-$(CONFIG_PWM_LPSS_PLATFORM)	+= pwm-lpss-platform.o
 obj-$(CONFIG_PWM_MESON)		+= pwm-meson.o
 obj-$(CONFIG_PWM_MEDIATEK)	+= pwm-mediatek.o
+obj-$(CONFIG_PWM_MICROCHIP_CORE)	+= pwm-microchip-core.o
 obj-$(CONFIG_PWM_MTK_DISP)	+= pwm-mtk-disp.o
 obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
 obj-$(CONFIG_PWM_NTXEC)		+= pwm-ntxec.o
diff --git a/drivers/pwm/pwm-microchip-core.c b/drivers/pwm/pwm-microchip-core.c
new file mode 100644
index 000000000000..2d12248f86b8
--- /dev/null
+++ b/drivers/pwm/pwm-microchip-core.c
@@ -0,0 +1,371 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * corePWM driver for Microchip "soft" FPGA IP cores.
+ *
+ * Copyright (c) 2021-2022 Microchip Corporation. All rights reserved.
+ * Author: Conor Dooley <conor.dooley@microchip.com>
+ * Documentation:
+ * https://www.microsemi.com/document-portal/doc_download/1245275-corepwm-hb
+ *
+ * Limitations:
+ * - If the IP block is configured without "shadow registers", all register
+ *   writes will take effect immediately, causing glitches on the output.
+ *   If shadow registers *are* enabled, a write to the "SYNC_UPDATE" register
+ *   notifies the core that it needs to update the registers defining the
+ *   waveform from the contents of the "shadow registers".
+ * - The IP block has no concept of a duty cycle, only rising/falling edges of
+ *   the waveform. Unfortunately, if the rising & falling edges registers have
+ *   the same value written to them the IP block will do whichever of a rising
+ *   or a falling edge is possible. I.E. a 50% waveform at twice the requested
+ *   period. Therefore to get a 0% waveform, the output is set the max high/low
+ *   time depending on polarity.
+ * - The PWM period is set for the whole IP block not per channel. The driver
+ *   will only change the period if no other PWM output is enabled.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/math.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#define PREG_TO_VAL(PREG) ((PREG) + 1)
+
+#define MCHPCOREPWM_PRESCALE_MAX	0x100
+#define MCHPCOREPWM_PERIOD_STEPS_MAX	0xff
+#define MCHPCOREPWM_PERIOD_MAX		0xff00
+
+#define MCHPCOREPWM_PRESCALE	0x00
+#define MCHPCOREPWM_PERIOD	0x04
+#define MCHPCOREPWM_EN(i)	(0x08 + 0x04 * (i)) /* 0x08, 0x0c */
+#define MCHPCOREPWM_POSEDGE(i)	(0x10 + 0x08 * (i)) /* 0x10, 0x18, ..., 0x88 */
+#define MCHPCOREPWM_NEGEDGE(i)	(0x14 + 0x08 * (i)) /* 0x14, 0x1c, ..., 0x8c */
+#define MCHPCOREPWM_SYNC_UPD	0xe4
+
+struct mchp_core_pwm_chip {
+	struct pwm_chip chip;
+	struct clk *clk;
+	struct mutex lock; /* protect the shared period */
+	void __iomem *base;
+	u32 sync_update_mask;
+	u16 channel_enabled;
+};
+
+static inline struct mchp_core_pwm_chip *to_mchp_core_pwm(struct pwm_chip *chip)
+{
+	return container_of(chip, struct mchp_core_pwm_chip, chip);
+}
+
+static void mchp_core_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
+				 bool enable, u64 period)
+{
+	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
+	u8 channel_enable, reg_offset, shift;
+
+	/*
+	 * There are two adjacent 8 bit control regs, the lower reg controls
+	 * 0-7 and the upper reg 8-15. Check if the pwm is in the upper reg
+	 * and if so, offset by the bus width.
+	 */
+	reg_offset = MCHPCOREPWM_EN(pwm->hwpwm >> 3);
+	shift = pwm->hwpwm & 7;
+
+	channel_enable = readb_relaxed(mchp_core_pwm->base + reg_offset);
+	channel_enable &= ~(1 << shift);
+	channel_enable |= (enable << shift);
+
+	writel_relaxed(channel_enable, mchp_core_pwm->base + reg_offset);
+	mchp_core_pwm->channel_enabled &= ~BIT(pwm->hwpwm);
+	mchp_core_pwm->channel_enabled |= enable << pwm->hwpwm;
+
+	/*
+	 * Notify the block to update the waveform from the shadow registers.
+	 * The updated values will not appear on the bus until they have been
+	 * applied to the waveform at the beginning of the next period. We must
+	 * write these registers and wait for them to be applied before calling
+	 * enable().
+	 */
+	if (mchp_core_pwm->sync_update_mask & (1 << pwm->hwpwm)) {
+		writel_relaxed(1U, mchp_core_pwm->base + MCHPCOREPWM_SYNC_UPD);
+		usleep_range(period, period * 2);
+	}
+}
+
+static u64 mchp_core_pwm_calc_duty(struct pwm_chip *chip, struct pwm_device *pwm,
+				   const struct pwm_state *state, u8 prescale, u8 period_steps)
+{
+	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
+	u64 duty_steps, period, tmp;
+	u16 prescale_val = PREG_TO_VAL(prescale);
+	u8 period_steps_val = PREG_TO_VAL(period_steps);
+
+	period = period_steps_val * prescale_val * NSEC_PER_SEC;
+	period = DIV64_U64_ROUND_UP(period, clk_get_rate(mchp_core_pwm->clk));
+
+	/*
+	 * Calculate the duty cycle in multiples of the prescaled period:
+	 * duty_steps = duty_in_ns / step_in_ns
+	 * step_in_ns = (prescale * NSEC_PER_SEC) / clk_rate
+	 * The code below is rearranged slightly to only divide once.
+	 */
+	duty_steps = state->duty_cycle * clk_get_rate(mchp_core_pwm->clk);
+	tmp = prescale_val * NSEC_PER_SEC;
+	return div64_u64(duty_steps, tmp);
+}
+
+static void mchp_core_pwm_apply_duty(struct pwm_chip *chip, struct pwm_device *pwm,
+				     const struct pwm_state *state, u64 duty_steps, u8 period_steps)
+{
+	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
+	u8 posedge, negedge;
+	u8 period_steps_val = PREG_TO_VAL(period_steps);
+
+	/*
+	 * Turn the output on unless posedge == negedge, in which case the
+	 * duty is intended to be 0, but limitations of the IP block don't
+	 * allow a zero length duty cycle - so just set the max high/low time
+	 * respectively.
+	 */
+	if (state->polarity == PWM_POLARITY_INVERSED) {
+		negedge = !duty_steps ? period_steps_val : 0u;
+		posedge = duty_steps;
+	} else {
+		posedge = !duty_steps ? period_steps_val : 0u;
+		negedge = duty_steps;
+	}
+
+	writel_relaxed(posedge, mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
+	writel_relaxed(negedge, mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
+}
+
+static int mchp_core_pwm_calc_period(struct pwm_chip *chip, const struct pwm_state *state,
+				     u8 *prescale, u8 *period_steps)
+{
+	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
+	u64 tmp, clk_rate;
+
+	/*
+	 * Calculate the period cycles and prescale values.
+	 * The registers are each 8 bits wide & multiplied to compute the period
+	 * using the formula:
+	 * (clock_period) * (prescale + 1) * (period_steps + 1)
+	 * so the maximum period that can be generated is 0x10000 times the
+	 * period of the input clock.
+	 * However, due to the design of the "hardware", it is not possible to
+	 * attain a 100% duty cycle if the full range of period_steps is used.
+	 * Therefore period_steps is restricted to 0xFE and the maximum multiple
+	 * of the clock period attainable is 0xFF00.
+	 */
+	clk_rate = clk_get_rate(mchp_core_pwm->clk);
+
+	/*
+	 * If clk_rate is too big, the following multiplication might overflow.
+	 * However this is implausible, as the fabric of current FPGAs cannot
+	 * provide clocks at a rate high enough.
+	 */
+	if (clk_rate >= NSEC_PER_SEC)
+		return -EINVAL;
+
+	tmp = mul_u64_u64_div_u64(state->period, clk_rate, NSEC_PER_SEC);
+
+	if (tmp >= MCHPCOREPWM_PERIOD_MAX) {
+		*prescale = MCHPCOREPWM_PRESCALE_MAX - 1;
+		*period_steps = MCHPCOREPWM_PERIOD_STEPS_MAX - 1;
+		return 0;
+	}
+
+	*prescale = div_u64(tmp, MCHPCOREPWM_PERIOD_STEPS_MAX);
+	/* PREG_TO_VAL() can produce a value larger than UINT8_MAX */
+	*period_steps = div_u64(tmp, PREG_TO_VAL((u32)*prescale)) - 1;
+
+	return 0;
+}
+
+static inline void mchp_core_pwm_apply_period(struct mchp_core_pwm_chip *mchp_core_pwm,
+					      u8 prescale, u8 period_steps)
+{
+	writel_relaxed(prescale, mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
+	writel_relaxed(period_steps, mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
+}
+
+static int mchp_core_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			       const struct pwm_state *state)
+{
+	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
+	struct pwm_state current_state = pwm->state;
+	bool period_locked;
+	u64 duty_steps;
+	u8 prescale, period_steps, hw_prescale, hw_period_steps;
+	int ret;
+
+	ret = mutex_lock_interruptible(&mchp_core_pwm->lock);
+	if (ret)
+		return ret;
+
+	if (!state->enabled) {
+		mchp_core_pwm_enable(chip, pwm, false, current_state.period);
+		mutex_unlock(&mchp_core_pwm->lock);
+		return 0;
+	}
+
+	/*
+	 * If the only thing that has changed is the duty cycle or the polarity,
+	 * we can shortcut the calculations and just compute/apply the new duty
+	 * cycle pos & neg edges
+	 * As all the channels share the same period, do not allow it to be
+	 * changed if any other channels are enabled.
+	 * If the period is locked, it may not be possible to use a period
+	 * less than that requested. In that case, we just abort.
+	 */
+	period_locked = mchp_core_pwm->channel_enabled & ~(1 << pwm->hwpwm);
+
+	if (period_locked) {
+		mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
+		hw_prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
+		hw_period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
+
+		if ((period_steps * prescale) < (hw_period_steps * hw_prescale)) {
+			mutex_unlock(&mchp_core_pwm->lock);
+			return -EINVAL;
+		}
+
+		prescale = hw_prescale;
+		period_steps = hw_period_steps;
+	} else if (!current_state.enabled || current_state.period != state->period) {
+		ret = mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
+		if (ret) {
+			mutex_unlock(&mchp_core_pwm->lock);
+			return ret;
+		}
+		mchp_core_pwm_apply_period(mchp_core_pwm, prescale, period_steps);
+	} else {
+		prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
+		period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
+	}
+
+	duty_steps = mchp_core_pwm_calc_duty(chip, pwm, state, prescale, period_steps);
+
+	/*
+	 * Because the period is per channel, it is possible that the requested
+	 * duty cycle is longer than the period, in which case cap it to the
+	 * period, IOW a 100% duty cycle.
+	 */
+	if (duty_steps > period_steps)
+		duty_steps = period_steps + 1;
+
+	mchp_core_pwm_apply_duty(chip, pwm, state, duty_steps, period_steps);
+
+	mchp_core_pwm_enable(chip, pwm, true, state->period);
+
+	mutex_unlock(&mchp_core_pwm->lock);
+
+	return 0;
+}
+
+static void mchp_core_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				    struct pwm_state *state)
+{
+	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
+	u16 prescale;
+	u8 period_steps, duty_steps, posedge, negedge;
+	int ret;
+
+	ret = mutex_lock_interruptible(&mchp_core_pwm->lock);
+	if (ret)
+		return;
+
+	if (mchp_core_pwm->channel_enabled & (1 << pwm->hwpwm))
+		state->enabled = true;
+	else
+		state->enabled = false;
+
+	prescale = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE));
+
+	period_steps = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD));
+	state->period = period_steps * prescale * NSEC_PER_SEC;
+	state->period = DIV64_U64_ROUND_UP(state->period, clk_get_rate(mchp_core_pwm->clk));
+
+	posedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
+	negedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
+
+	if (negedge == posedge) {
+		state->duty_cycle = state->period / 2;
+	} else {
+		duty_steps = abs((s16)posedge - (s16)negedge);
+		state->duty_cycle = duty_steps * prescale * NSEC_PER_SEC;
+		state->duty_cycle = DIV64_U64_ROUND_UP(state->duty_cycle,
+						       clk_get_rate(mchp_core_pwm->clk));
+	}
+
+	state->polarity = negedge < posedge ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
+
+	mutex_unlock(&mchp_core_pwm->lock);
+}
+
+static const struct pwm_ops mchp_core_pwm_ops = {
+	.apply = mchp_core_pwm_apply,
+	.get_state = mchp_core_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static const struct of_device_id mchp_core_of_match[] = {
+	{
+		.compatible = "microchip,corepwm-rtl-v4",
+	},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mchp_core_of_match);
+
+static int mchp_core_pwm_probe(struct platform_device *pdev)
+{
+	struct mchp_core_pwm_chip *mchp_pwm;
+	struct resource *regs;
+	int ret;
+
+	mchp_pwm = devm_kzalloc(&pdev->dev, sizeof(*mchp_pwm), GFP_KERNEL);
+	if (!mchp_pwm)
+		return -ENOMEM;
+
+	mchp_pwm->base = devm_platform_get_and_ioremap_resource(pdev, 0, &regs);
+	if (IS_ERR(mchp_pwm->base))
+		return PTR_ERR(mchp_pwm->base);
+
+	mchp_pwm->clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	if (IS_ERR(mchp_pwm->clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(mchp_pwm->clk),
+				     "failed to get PWM clock\n");
+
+	if (of_property_read_u32(pdev->dev.of_node, "microchip,sync-update-mask",
+				 &mchp_pwm->sync_update_mask))
+		mchp_pwm->sync_update_mask = 0u;
+
+	mutex_init(&mchp_pwm->lock);
+
+	mchp_pwm->chip.dev = &pdev->dev;
+	mchp_pwm->chip.ops = &mchp_core_pwm_ops;
+	mchp_pwm->chip.npwm = 16;
+
+	ret = devm_pwmchip_add(&pdev->dev, &mchp_pwm->chip);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");
+
+	return 0;
+}
+
+static struct platform_driver mchp_core_pwm_driver = {
+	.driver = {
+		.name = "mchp-core-pwm",
+		.of_match_table = mchp_core_of_match,
+	},
+	.probe = mchp_core_pwm_probe,
+};
+module_platform_driver(mchp_core_pwm_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Conor Dooley <conor.dooley@microchip.com>");
+MODULE_DESCRIPTION("corePWM driver for Microchip FPGAs");
-- 
2.37.1

Re: [PATCH v7 3/4] pwm: add microchip soft ip corePWM driver

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 17757 bytes --]

Hello,

On Thu, Jul 21, 2022 at 06:21:09PM +0100, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> Add a driver that supports the Microchip FPGA "soft" PWM IP core.
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  drivers/pwm/Kconfig              |  10 +
>  drivers/pwm/Makefile             |   1 +
>  drivers/pwm/pwm-microchip-core.c | 371 +++++++++++++++++++++++++++++++
>  3 files changed, 382 insertions(+)
>  create mode 100644 drivers/pwm/pwm-microchip-core.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 904de8d61828..007ea5750e73 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -383,6 +383,16 @@ config PWM_MEDIATEK
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-mediatek.
>  
> +config PWM_MICROCHIP_CORE
> +	tristate "Microchip corePWM PWM support"
> +	depends on SOC_MICROCHIP_POLARFIRE || COMPILE_TEST
> +	depends on HAS_IOMEM && OF
> +	help
> +	  PWM driver for Microchip FPGA soft IP core.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-microchip-core.
> +
>  config PWM_MXS
>  	tristate "Freescale MXS PWM support"
>  	depends on ARCH_MXS || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 5c08bdb817b4..43feb7cfc66a 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -33,6 +33,7 @@ obj-$(CONFIG_PWM_LPSS_PCI)	+= pwm-lpss-pci.o
>  obj-$(CONFIG_PWM_LPSS_PLATFORM)	+= pwm-lpss-platform.o
>  obj-$(CONFIG_PWM_MESON)		+= pwm-meson.o
>  obj-$(CONFIG_PWM_MEDIATEK)	+= pwm-mediatek.o
> +obj-$(CONFIG_PWM_MICROCHIP_CORE)	+= pwm-microchip-core.o
>  obj-$(CONFIG_PWM_MTK_DISP)	+= pwm-mtk-disp.o
>  obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
>  obj-$(CONFIG_PWM_NTXEC)		+= pwm-ntxec.o
> diff --git a/drivers/pwm/pwm-microchip-core.c b/drivers/pwm/pwm-microchip-core.c
> new file mode 100644
> index 000000000000..2d12248f86b8
> --- /dev/null
> +++ b/drivers/pwm/pwm-microchip-core.c
> @@ -0,0 +1,371 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * corePWM driver for Microchip "soft" FPGA IP cores.
> + *
> + * Copyright (c) 2021-2022 Microchip Corporation. All rights reserved.
> + * Author: Conor Dooley <conor.dooley@microchip.com>
> + * Documentation:
> + * https://www.microsemi.com/document-portal/doc_download/1245275-corepwm-hb
> + *
> + * Limitations:
> + * - If the IP block is configured without "shadow registers", all register
> + *   writes will take effect immediately, causing glitches on the output.
> + *   If shadow registers *are* enabled, a write to the "SYNC_UPDATE" register
> + *   notifies the core that it needs to update the registers defining the
> + *   waveform from the contents of the "shadow registers".
> + * - The IP block has no concept of a duty cycle, only rising/falling edges of
> + *   the waveform. Unfortunately, if the rising & falling edges registers have
> + *   the same value written to them the IP block will do whichever of a rising
> + *   or a falling edge is possible. I.E. a 50% waveform at twice the requested
> + *   period. Therefore to get a 0% waveform, the output is set the max high/low
> + *   time depending on polarity.
> + * - The PWM period is set for the whole IP block not per channel. The driver
> + *   will only change the period if no other PWM output is enabled.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/math.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +
> +#define PREG_TO_VAL(PREG) ((PREG) + 1)
> +
> +#define MCHPCOREPWM_PRESCALE_MAX	0x100
> +#define MCHPCOREPWM_PERIOD_STEPS_MAX	0xff
> +#define MCHPCOREPWM_PERIOD_MAX		0xff00
> +
> +#define MCHPCOREPWM_PRESCALE	0x00
> +#define MCHPCOREPWM_PERIOD	0x04
> +#define MCHPCOREPWM_EN(i)	(0x08 + 0x04 * (i)) /* 0x08, 0x0c */
> +#define MCHPCOREPWM_POSEDGE(i)	(0x10 + 0x08 * (i)) /* 0x10, 0x18, ..., 0x88 */
> +#define MCHPCOREPWM_NEGEDGE(i)	(0x14 + 0x08 * (i)) /* 0x14, 0x1c, ..., 0x8c */
> +#define MCHPCOREPWM_SYNC_UPD	0xe4
> +
> +struct mchp_core_pwm_chip {
> +	struct pwm_chip chip;
> +	struct clk *clk;
> +	struct mutex lock; /* protect the shared period */
> +	void __iomem *base;
> +	u32 sync_update_mask;
> +	u16 channel_enabled;
> +};
> +
> +static inline struct mchp_core_pwm_chip *to_mchp_core_pwm(struct pwm_chip *chip)
> +{
> +	return container_of(chip, struct mchp_core_pwm_chip, chip);
> +}
> +
> +static void mchp_core_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
> +				 bool enable, u64 period)
> +{
> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> +	u8 channel_enable, reg_offset, shift;
> +
> +	/*
> +	 * There are two adjacent 8 bit control regs, the lower reg controls
> +	 * 0-7 and the upper reg 8-15. Check if the pwm is in the upper reg
> +	 * and if so, offset by the bus width.
> +	 */
> +	reg_offset = MCHPCOREPWM_EN(pwm->hwpwm >> 3);
> +	shift = pwm->hwpwm & 7;
> +
> +	channel_enable = readb_relaxed(mchp_core_pwm->base + reg_offset);
> +	channel_enable &= ~(1 << shift);
> +	channel_enable |= (enable << shift);
> +
> +	writel_relaxed(channel_enable, mchp_core_pwm->base + reg_offset);
> +	mchp_core_pwm->channel_enabled &= ~BIT(pwm->hwpwm);
> +	mchp_core_pwm->channel_enabled |= enable << pwm->hwpwm;
> +
> +	/*
> +	 * Notify the block to update the waveform from the shadow registers.
> +	 * The updated values will not appear on the bus until they have been
> +	 * applied to the waveform at the beginning of the next period. We must
> +	 * write these registers and wait for them to be applied before calling
> +	 * enable().

What does "calling enable()" mean? There is no such function or callback
with that name?!

> +	 */
> +	if (mchp_core_pwm->sync_update_mask & (1 << pwm->hwpwm)) {
> +		writel_relaxed(1U, mchp_core_pwm->base + MCHPCOREPWM_SYNC_UPD);
> +		usleep_range(period, period * 2);

So if period = 5000 *ns* you sleep between 5000 and 10000 *us* here?

> +	}
> +}
> +
> +static u64 mchp_core_pwm_calc_duty(struct pwm_chip *chip, struct pwm_device *pwm,
> +				   const struct pwm_state *state, u8 prescale, u8 period_steps)
> +{
> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> +	u64 duty_steps, period, tmp;
> +	u16 prescale_val = PREG_TO_VAL(prescale);
> +	u8 period_steps_val = PREG_TO_VAL(period_steps);

Can it happen that period_steps is 0xff? Then period_steps_val ends up
being 0.

> +
> +	period = period_steps_val * prescale_val * NSEC_PER_SEC;
> +	period = DIV64_U64_ROUND_UP(period, clk_get_rate(mchp_core_pwm->clk));

The value you are calculating for period isn't used?!

> +
> +	/*
> +	 * Calculate the duty cycle in multiples of the prescaled period:
> +	 * duty_steps = duty_in_ns / step_in_ns
> +	 * step_in_ns = (prescale * NSEC_PER_SEC) / clk_rate
> +	 * The code below is rearranged slightly to only divide once.
> +	 */
> +	duty_steps = state->duty_cycle * clk_get_rate(mchp_core_pwm->clk);
> +	tmp = prescale_val * NSEC_PER_SEC;
> +	return div64_u64(duty_steps, tmp);
> +}
> +
> +static void mchp_core_pwm_apply_duty(struct pwm_chip *chip, struct pwm_device *pwm,
> +				     const struct pwm_state *state, u64 duty_steps, u8 period_steps)
> +{
> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> +	u8 posedge, negedge;
> +	u8 period_steps_val = PREG_TO_VAL(period_steps);
> +
> +	/*
> +	 * Turn the output on unless posedge == negedge, in which case the
> +	 * duty is intended to be 0, but limitations of the IP block don't
> +	 * allow a zero length duty cycle - so just set the max high/low time
> +	 * respectively.
> +	 */

I don't understand that comment. Maybe you mean?:

	/*
	 * Setting posedge == negedge doesn't yield a constant output,
	 * so that's an unsuitable setting to model duty_steps = 0.
	 * In that case set the unwanted edge to a value that never
	 * triggers.
	 */

> +	if (state->polarity == PWM_POLARITY_INVERSED) {
> +		negedge = !duty_steps ? period_steps_val : 0u;
> +		posedge = duty_steps;
> +	} else {
> +		posedge = !duty_steps ? period_steps_val : 0u;
> +		negedge = duty_steps;
> +	}
> +
> +	writel_relaxed(posedge, mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
> +	writel_relaxed(negedge, mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
> +}
> +
> +static int mchp_core_pwm_calc_period(struct pwm_chip *chip, const struct pwm_state *state,
> +				     u8 *prescale, u8 *period_steps)
> +{
> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> +	u64 tmp, clk_rate;
> +
> +	/*
> +	 * Calculate the period cycles and prescale values.
> +	 * The registers are each 8 bits wide & multiplied to compute the period
> +	 * using the formula:
> +	 * (clock_period) * (prescale + 1) * (period_steps + 1)
> +	 * so the maximum period that can be generated is 0x10000 times the
> +	 * period of the input clock.
> +	 * However, due to the design of the "hardware", it is not possible to
> +	 * attain a 100% duty cycle if the full range of period_steps is used.
> +	 * Therefore period_steps is restricted to 0xFE and the maximum multiple
> +	 * of the clock period attainable is 0xFF00.
> +	 */
> +	clk_rate = clk_get_rate(mchp_core_pwm->clk);
> +
> +	/*
> +	 * If clk_rate is too big, the following multiplication might overflow.
> +	 * However this is implausible, as the fabric of current FPGAs cannot
> +	 * provide clocks at a rate high enough.
> +	 */
> +	if (clk_rate >= NSEC_PER_SEC)
> +		return -EINVAL;
> +
> +	tmp = mul_u64_u64_div_u64(state->period, clk_rate, NSEC_PER_SEC);
> +
> +	if (tmp >= MCHPCOREPWM_PERIOD_MAX) {
> +		*prescale = MCHPCOREPWM_PRESCALE_MAX - 1;

why -1 here?

> +		*period_steps = MCHPCOREPWM_PERIOD_STEPS_MAX - 1;
> +		return 0;
> +	}
> +
> +	*prescale = div_u64(tmp, MCHPCOREPWM_PERIOD_STEPS_MAX);
> +	/* PREG_TO_VAL() can produce a value larger than UINT8_MAX */

That should explain the cast to u32? If this were really necessary
(hint: it isn't) it would IMHO be better to hide that cast in the macro.

> +	*period_steps = div_u64(tmp, PREG_TO_VAL((u32)*prescale)) - 1;
> +
> +	return 0;
> +}
> +
> +static inline void mchp_core_pwm_apply_period(struct mchp_core_pwm_chip *mchp_core_pwm,
> +					      u8 prescale, u8 period_steps)
> +{
> +	writel_relaxed(prescale, mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
> +	writel_relaxed(period_steps, mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
> +}
> +
> +static int mchp_core_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			       const struct pwm_state *state)
> +{
> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> +	struct pwm_state current_state = pwm->state;
> +	bool period_locked;
> +	u64 duty_steps;
> +	u8 prescale, period_steps, hw_prescale, hw_period_steps;
> +	int ret;
> +
> +	ret = mutex_lock_interruptible(&mchp_core_pwm->lock);
> +	if (ret)
> +		return ret;

I would have used mutex_lock() here. Why should a signal prevent
reconfiguration of the PWM?

> +
> +	if (!state->enabled) {
> +		mchp_core_pwm_enable(chip, pwm, false, current_state.period);
> +		mutex_unlock(&mchp_core_pwm->lock);
> +		return 0;
> +	}
> +
> +	/*
> +	 * If the only thing that has changed is the duty cycle or the polarity,
> +	 * we can shortcut the calculations and just compute/apply the new duty
> +	 * cycle pos & neg edges
> +	 * As all the channels share the same period, do not allow it to be
> +	 * changed if any other channels are enabled.
> +	 * If the period is locked, it may not be possible to use a period
> +	 * less than that requested. In that case, we just abort.
> +	 */
> +	period_locked = mchp_core_pwm->channel_enabled & ~(1 << pwm->hwpwm);
> +
> +	if (period_locked) {
> +		mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
> +		hw_prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
> +		hw_period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
> +
> +		if ((period_steps * prescale) < (hw_period_steps * hw_prescale)) {

You need

	if ((period_steps + 1) * (prescale + 1) < (hw_period_steps + 1) * (hw_prescale + 1))

here, don't you?

> +			mutex_unlock(&mchp_core_pwm->lock);
> +			return -EINVAL;
> +		}
> +
> +		prescale = hw_prescale;
> +		period_steps = hw_period_steps;

The two hw_* variables are only used in this branch. So their
declaration can move into here.

> +	} else if (!current_state.enabled || current_state.period != state->period) {
> +		ret = mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
> +		if (ret) {
> +			mutex_unlock(&mchp_core_pwm->lock);
> +			return ret;
> +		}
> +		mchp_core_pwm_apply_period(mchp_core_pwm, prescale, period_steps);
> +	} else {
> +		prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
> +		period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
> +	}
> +
> +	duty_steps = mchp_core_pwm_calc_duty(chip, pwm, state, prescale, period_steps);
> +
> +	/*
> +	 * Because the period is per channel, it is possible that the requested
> +	 * duty cycle is longer than the period, in which case cap it to the
> +	 * period, IOW a 100% duty cycle.
> +	 */
> +	if (duty_steps > period_steps)
> +		duty_steps = period_steps + 1;
> +
> +	mchp_core_pwm_apply_duty(chip, pwm, state, duty_steps, period_steps);
> +
> +	mchp_core_pwm_enable(chip, pwm, true, state->period);
> +
> +	mutex_unlock(&mchp_core_pwm->lock);
> +
> +	return 0;
> +}
> +
> +static void mchp_core_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> +				    struct pwm_state *state)
> +{
> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
> +	u16 prescale;
> +	u8 period_steps, duty_steps, posedge, negedge;
> +	int ret;
> +
> +	ret = mutex_lock_interruptible(&mchp_core_pwm->lock);
> +	if (ret)
> +		return;
> +
> +	if (mchp_core_pwm->channel_enabled & (1 << pwm->hwpwm))

channel_enabled is initialized to 0 in .probe(), so a PWM is never
diagnosed to be running when the core initially wants to determine the
current state.

> +		state->enabled = true;
> +	else
> +		state->enabled = false;
> +
> +	prescale = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE));
> +
> +	period_steps = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD));
> +	state->period = period_steps * prescale * NSEC_PER_SEC;
> +	state->period = DIV64_U64_ROUND_UP(state->period, clk_get_rate(mchp_core_pwm->clk));
> +
> +	posedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
> +	negedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
> +
> +	if (negedge == posedge) {
> +		state->duty_cycle = state->period / 2;

I thought that's:

		state->duty_cycle = state->period;
		state->period *= 2;

?

> +	} else {
> +		duty_steps = abs((s16)posedge - (s16)negedge);
> +		state->duty_cycle = duty_steps * prescale * NSEC_PER_SEC;
> +		state->duty_cycle = DIV64_U64_ROUND_UP(state->duty_cycle,
> +						       clk_get_rate(mchp_core_pwm->clk));
> +	}
> +
> +	state->polarity = negedge < posedge ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
> +
> +	mutex_unlock(&mchp_core_pwm->lock);
> +}
> +
> +static const struct pwm_ops mchp_core_pwm_ops = {
> +	.apply = mchp_core_pwm_apply,
> +	.get_state = mchp_core_pwm_get_state,
> +	.owner = THIS_MODULE,
> +};
> +
> +static const struct of_device_id mchp_core_of_match[] = {
> +	{
> +		.compatible = "microchip,corepwm-rtl-v4",
> +	},
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mchp_core_of_match);
> +
> +static int mchp_core_pwm_probe(struct platform_device *pdev)
> +{
> +	struct mchp_core_pwm_chip *mchp_pwm;
> +	struct resource *regs;
> +	int ret;
> +
> +	mchp_pwm = devm_kzalloc(&pdev->dev, sizeof(*mchp_pwm), GFP_KERNEL);
> +	if (!mchp_pwm)
> +		return -ENOMEM;
> +
> +	mchp_pwm->base = devm_platform_get_and_ioremap_resource(pdev, 0, &regs);
> +	if (IS_ERR(mchp_pwm->base))
> +		return PTR_ERR(mchp_pwm->base);
> +
> +	mchp_pwm->clk = devm_clk_get_enabled(&pdev->dev, NULL);
> +	if (IS_ERR(mchp_pwm->clk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(mchp_pwm->clk),
> +				     "failed to get PWM clock\n");
> +
> +	if (of_property_read_u32(pdev->dev.of_node, "microchip,sync-update-mask",
> +				 &mchp_pwm->sync_update_mask))
> +		mchp_pwm->sync_update_mask = 0u;
> +
> +	mutex_init(&mchp_pwm->lock);
> +
> +	mchp_pwm->chip.dev = &pdev->dev;
> +	mchp_pwm->chip.ops = &mchp_core_pwm_ops;
> +	mchp_pwm->chip.npwm = 16;
> +
> +	ret = devm_pwmchip_add(&pdev->dev, &mchp_pwm->chip);
> +	if (ret < 0)
> +		return dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");
> +
> +	return 0;
> +}
> +
> +static struct platform_driver mchp_core_pwm_driver = {
> +	.driver = {
> +		.name = "mchp-core-pwm",
> +		.of_match_table = mchp_core_of_match,
> +	},
> +	.probe = mchp_core_pwm_probe,
> +};
> +module_platform_driver(mchp_core_pwm_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Conor Dooley <conor.dooley@microchip.com>");
> +MODULE_DESCRIPTION("corePWM driver for Microchip FPGAs");

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH v7 3/4] pwm: add microchip soft ip corePWM driver

[Conor.Dooley]

On 02/08/2022 09:46, Uwe Kleine-König wrote:
> Hello,
> 
> On Thu, Jul 21, 2022 at 06:21:09PM +0100, Conor Dooley wrote:
>> From: Conor Dooley <conor.dooley@microchip.com>
>>
>> Add a driver that supports the Microchip FPGA "soft" PWM IP core.
>>
>> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>> ---

>> +static void mchp_core_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
>> +				 bool enable, u64 period)
>> +{
>> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
>> +	u8 channel_enable, reg_offset, shift;
>> +
>> +	/*
>> +	 * There are two adjacent 8 bit control regs, the lower reg controls
>> +	 * 0-7 and the upper reg 8-15. Check if the pwm is in the upper reg
>> +	 * and if so, offset by the bus width.
>> +	 */
>> +	reg_offset = MCHPCOREPWM_EN(pwm->hwpwm >> 3);
>> +	shift = pwm->hwpwm & 7;
>> +
>> +	channel_enable = readb_relaxed(mchp_core_pwm->base + reg_offset);
>> +	channel_enable &= ~(1 << shift);
>> +	channel_enable |= (enable << shift);
>> +
>> +	writel_relaxed(channel_enable, mchp_core_pwm->base + reg_offset);
>> +	mchp_core_pwm->channel_enabled &= ~BIT(pwm->hwpwm);
>> +	mchp_core_pwm->channel_enabled |= enable << pwm->hwpwm;
>> +
>> +	/*
>> +	 * Notify the block to update the waveform from the shadow registers.
>> +	 * The updated values will not appear on the bus until they have been
>> +	 * applied to the waveform at the beginning of the next period. We must
>> +	 * write these registers and wait for them to be applied before calling
>> +	 * enable().
> 
> What does "calling enable()" mean? There is no such function or callback
> with that name?!

I relocated the comment but forgot to proof read it!
s/calling enable()/considering the channel enabled/
I'm not sure where it comes from, but I keep thinking that there is an
enable() callback...

> 
>> +	 */
>> +	if (mchp_core_pwm->sync_update_mask & (1 << pwm->hwpwm)) {
>> +		writel_relaxed(1U, mchp_core_pwm->base + MCHPCOREPWM_SYNC_UPD);
>> +		usleep_range(period, period * 2);
> 
> So if period = 5000 *ns* you sleep between 5000 and 10000 *us* here?

/facepalm

> 
>> +	}
>> +}
>> +
>> +static u64 mchp_core_pwm_calc_duty(struct pwm_chip *chip, struct pwm_device *pwm,
>> +				   const struct pwm_state *state, u8 prescale, u8 period_steps)
>> +{
>> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
>> +	u64 duty_steps, period, tmp;
>> +	u16 prescale_val = PREG_TO_VAL(prescale);
>> +	u8 period_steps_val = PREG_TO_VAL(period_steps);
> 
> Can it happen that period_steps is 0xff? Then period_steps_val ends up
> being 0.

I guess that register could have a value it in from the bootloader etc and
therefore handling it is a good idea - but not in this function since it
is never used...

> 
>> +
>> +	period = period_steps_val * prescale_val * NSEC_PER_SEC;
>> +	period = DIV64_U64_ROUND_UP(period, clk_get_rate(mchp_core_pwm->clk));
> 
> The value you are calculating for period isn't used?!

huh, I am surprised that this was not caught by a W=1 C=1 build. Or maybe it
was and I just didn't notice - but I am 99% sure I made sure there were none.

> 
>> +
>> +	/*
>> +	 * Calculate the duty cycle in multiples of the prescaled period:
>> +	 * duty_steps = duty_in_ns / step_in_ns
>> +	 * step_in_ns = (prescale * NSEC_PER_SEC) / clk_rate
>> +	 * The code below is rearranged slightly to only divide once.
>> +	 */
>> +	duty_steps = state->duty_cycle * clk_get_rate(mchp_core_pwm->clk);
>> +	tmp = prescale_val * NSEC_PER_SEC;
>> +	return div64_u64(duty_steps, tmp);
>> +}
>> +
>> +static void mchp_core_pwm_apply_duty(struct pwm_chip *chip, struct pwm_device *pwm,
>> +				     const struct pwm_state *state, u64 duty_steps, u8 period_steps)
>> +{
>> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
>> +	u8 posedge, negedge;
>> +	u8 period_steps_val = PREG_TO_VAL(period_steps);
>> +
>> +	/*
>> +	 * Turn the output on unless posedge == negedge, in which case the
>> +	 * duty is intended to be 0, but limitations of the IP block don't
>> +	 * allow a zero length duty cycle - so just set the max high/low time
>> +	 * respectively.
>> +	 */
> 
> I don't understand that comment. Maybe you mean?:
> 
> 	/*
> 	 * Setting posedge == negedge doesn't yield a constant output,
> 	 * so that's an unsuitable setting to model duty_steps = 0.
> 	 * In that case set the unwanted edge to a value that never
> 	 * triggers.
> 	 */

Yeah, this is a better comment. Thanks.

> 
>> +	if (state->polarity == PWM_POLARITY_INVERSED) {
>> +		negedge = !duty_steps ? period_steps_val : 0u;
>> +		posedge = duty_steps;
>> +	} else {
>> +		posedge = !duty_steps ? period_steps_val : 0u;
>> +		negedge = duty_steps;
>> +	}
>> +
>> +	writel_relaxed(posedge, mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
>> +	writel_relaxed(negedge, mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
>> +}
>> +
>> +static int mchp_core_pwm_calc_period(struct pwm_chip *chip, const struct pwm_state *state,
>> +				     u8 *prescale, u8 *period_steps)
>> +{
>> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
>> +	u64 tmp, clk_rate;
>> +
>> +	/*
>> +	 * Calculate the period cycles and prescale values.
>> +	 * The registers are each 8 bits wide & multiplied to compute the period
>> +	 * using the formula:
>> +	 * (clock_period) * (prescale + 1) * (period_steps + 1)
>> +	 * so the maximum period that can be generated is 0x10000 times the
>> +	 * period of the input clock.
>> +	 * However, due to the design of the "hardware", it is not possible to
>> +	 * attain a 100% duty cycle if the full range of period_steps is used.
>> +	 * Therefore period_steps is restricted to 0xFE and the maximum multiple
>> +	 * of the clock period attainable is 0xFF00.
>> +	 */
>> +	clk_rate = clk_get_rate(mchp_core_pwm->clk);
>> +
>> +	/*
>> +	 * If clk_rate is too big, the following multiplication might overflow.
>> +	 * However this is implausible, as the fabric of current FPGAs cannot
>> +	 * provide clocks at a rate high enough.
>> +	 */
>> +	if (clk_rate >= NSEC_PER_SEC)
>> +		return -EINVAL;
>> +
>> +	tmp = mul_u64_u64_div_u64(state->period, clk_rate, NSEC_PER_SEC);
>> +
>> +	if (tmp >= MCHPCOREPWM_PERIOD_MAX) {
>> +		*prescale = MCHPCOREPWM_PRESCALE_MAX - 1;
> 
> why -1 here?

Because the hardware adds 1 to the register value. I had tried to explain
in the large comment above, but I will reword the comment for v8.

> 
>> +		*period_steps = MCHPCOREPWM_PERIOD_STEPS_MAX - 1;
>> +		return 0;
>> +	}
>> +
>> +	*prescale = div_u64(tmp, MCHPCOREPWM_PERIOD_STEPS_MAX);
>> +	/* PREG_TO_VAL() can produce a value larger than UINT8_MAX */
> 
> That should explain the cast to u32? If this were really necessary
> (hint: it isn't) it would IMHO be better to hide that cast in the macro.
> 
>> +	*period_steps = div_u64(tmp, PREG_TO_VAL((u32)*prescale)) - 1;
>> +
>> +	return 0;
>> +}
>> +
>> +static inline void mchp_core_pwm_apply_period(struct mchp_core_pwm_chip *mchp_core_pwm,
>> +					      u8 prescale, u8 period_steps)
>> +{
>> +	writel_relaxed(prescale, mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
>> +	writel_relaxed(period_steps, mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
>> +}
>> +
>> +static int mchp_core_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>> +			       const struct pwm_state *state)
>> +{
>> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
>> +	struct pwm_state current_state = pwm->state;
>> +	bool period_locked;
>> +	u64 duty_steps;
>> +	u8 prescale, period_steps, hw_prescale, hw_period_steps;
>> +	int ret;
>> +
>> +	ret = mutex_lock_interruptible(&mchp_core_pwm->lock);
>> +	if (ret)
>> +		return ret;
> 
> I would have used mutex_lock() here. Why should a signal prevent
> reconfiguration of the PWM?

Cool, willdo.

> 
>> +
>> +	if (!state->enabled) {
>> +		mchp_core_pwm_enable(chip, pwm, false, current_state.period);
>> +		mutex_unlock(&mchp_core_pwm->lock);
>> +		return 0;
>> +	}
>> +
>> +	/*
>> +	 * If the only thing that has changed is the duty cycle or the polarity,
>> +	 * we can shortcut the calculations and just compute/apply the new duty
>> +	 * cycle pos & neg edges
>> +	 * As all the channels share the same period, do not allow it to be
>> +	 * changed if any other channels are enabled.
>> +	 * If the period is locked, it may not be possible to use a period
>> +	 * less than that requested. In that case, we just abort.
>> +	 */
>> +	period_locked = mchp_core_pwm->channel_enabled & ~(1 << pwm->hwpwm);
>> +
>> +	if (period_locked) {
>> +		mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
>> +		hw_prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
>> +		hw_period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
>> +
>> +		if ((period_steps * prescale) < (hw_period_steps * hw_prescale)) {
> 
> You need
> 
> 	if ((period_steps + 1) * (prescale + 1) < (hw_period_steps + 1) * (hw_prescale + 1))
> 
> here, don't you?

Yikes, yeah...

> 
>> +			mutex_unlock(&mchp_core_pwm->lock);
>> +			return -EINVAL;
>> +		}
>> +
>> +		prescale = hw_prescale;
>> +		period_steps = hw_period_steps;
> 
> The two hw_* variables are only used in this branch. So their
> declaration can move into here.
> 
>> +	} else if (!current_state.enabled || current_state.period != state->period) {
>> +		ret = mchp_core_pwm_calc_period(chip, state, &prescale, &period_steps);
>> +		if (ret) {
>> +			mutex_unlock(&mchp_core_pwm->lock);
>> +			return ret;
>> +		}
>> +		mchp_core_pwm_apply_period(mchp_core_pwm, prescale, period_steps);
>> +	} else {
>> +		prescale = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE);
>> +		period_steps = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD);
>> +	}
>> +
>> +	duty_steps = mchp_core_pwm_calc_duty(chip, pwm, state, prescale, period_steps);
>> +
>> +	/*
>> +	 * Because the period is per channel, it is possible that the requested
>> +	 * duty cycle is longer than the period, in which case cap it to the
>> +	 * period, IOW a 100% duty cycle.
>> +	 */
>> +	if (duty_steps > period_steps)
>> +		duty_steps = period_steps + 1;
>> +
>> +	mchp_core_pwm_apply_duty(chip, pwm, state, duty_steps, period_steps);
>> +
>> +	mchp_core_pwm_enable(chip, pwm, true, state->period);
>> +
>> +	mutex_unlock(&mchp_core_pwm->lock);
>> +
>> +	return 0;
>> +}
>> +
>> +static void mchp_core_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>> +				    struct pwm_state *state)
>> +{
>> +	struct mchp_core_pwm_chip *mchp_core_pwm = to_mchp_core_pwm(chip);
>> +	u16 prescale;
>> +	u8 period_steps, duty_steps, posedge, negedge;
>> +	int ret;
>> +
>> +	ret = mutex_lock_interruptible(&mchp_core_pwm->lock);
>> +	if (ret)
>> +		return;
>> +
>> +	if (mchp_core_pwm->channel_enabled & (1 << pwm->hwpwm))
> 
> channel_enabled is initialized to 0 in .probe(), so a PWM is never
> diagnosed to be running when the core initially wants to determine the
> current state.

Good point. I'll initialise it in probe.

> 
>> +		state->enabled = true;
>> +	else
>> +		state->enabled = false;
>> +
>> +	prescale = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PRESCALE));
>> +
>> +	period_steps = PREG_TO_VAL(readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_PERIOD));
>> +	state->period = period_steps * prescale * NSEC_PER_SEC;
>> +	state->period = DIV64_U64_ROUND_UP(state->period, clk_get_rate(mchp_core_pwm->clk));
>> +
>> +	posedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_POSEDGE(pwm->hwpwm));
>> +	negedge = readb_relaxed(mchp_core_pwm->base + MCHPCOREPWM_NEGEDGE(pwm->hwpwm));
>> +
>> +	if (negedge == posedge) {
>> +		state->duty_cycle = state->period / 2;
> 
> I thought that's:
> 
> 		state->duty_cycle = state->period;
> 		state->period *= 2;

Correct, as usual..
Thanks for your review Uwe! I'll fix it all up & submit v8 after -rc1.
Conor.

Re: [PATCH v7 3/4] pwm: add microchip soft ip corePWM driver

[Uwe Kleine-König]

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Hello Conor,

On Tue, Aug 02, 2022 at 12:34:14PM +0000, Conor.Dooley@microchip.com wrote:
> I'll fix it all up & submit v8 after -rc1.

I discard the whole series in patchwork in the expectation that all
patches will be part of your v8.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH v7 3/4] pwm: add microchip soft ip corePWM driver

[Conor.Dooley]

On 05/08/2022 20:58, Uwe Kleine-König wrote:
> Hello Conor,
> 
> On Tue, Aug 02, 2022 at 12:34:14PM +0000, Conor.Dooley@microchip.com wrote:
>> I'll fix it all up & submit v8 after -rc1.
> 
> I discard the whole series in patchwork in the expectation that all
> patches will be part of your v8.

That was my plan, don't think there's a rush on the dt-binding fix.
Thanks Uwe,
Conor.

[PATCH v7 4/4] MAINTAINERS: add pwm to PolarFire SoC entry

[Conor Dooley]

From: Conor Dooley <conor.dooley@microchip.com>

Add the newly introduced pwm driver to the existing PolarFire SoC entry.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 MAINTAINERS | 1 +
 1 file changed, 1 insertion(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 7d14a446df13..c785765c66b7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17510,6 +17510,7 @@ F:	drivers/char/hw_random/mpfs-rng.c
 F:	drivers/clk/microchip/clk-mpfs.c
 F:	drivers/mailbox/mailbox-mpfs.c
 F:	drivers/pci/controller/pcie-microchip-host.c
+F:	drivers/pwm/pwm-microchip-core.c
 F:	drivers/rtc/rtc-mpfs.c
 F:	drivers/soc/microchip/
 F:	drivers/spi/spi-microchip-core.c
-- 
2.37.1