Re: [PATCH v10 07/17] media: mali-c55: Add Mali-C55 ISP driver

Sakari Ailus
2025-06-28T20:08:49Z

Hi Daniel,

On 6/24/25 13:21, Daniel Scally wrote:

...

> +static irqreturn_t mali_c55_isr(int irq, void *context)
> +{
> + struct device *dev = context;
> + struct mali_c55 *mali_c55 = dev_get_drvdata(dev);
> + u32 interrupt_status;
> + unsigned int i;
> +
> + interrupt_status = mali_c55_read(mali_c55,
> + MALI_C55_REG_INTERRUPT_STATUS_VECTOR);
> + if (!interrupt_status)
> + return IRQ_NONE;
> +
> + mali_c55_write(mali_c55, MALI_C55_REG_INTERRUPT_CLEAR_VECTOR,
> + interrupt_status);
> + mali_c55_write(mali_c55, MALI_C55_REG_INTERRUPT_CLEAR, 0);
> + mali_c55_write(mali_c55, MALI_C55_REG_INTERRUPT_CLEAR, 1);
> +
> + for (i = 0; i < MALI_C55_NUM_IRQ_BITS; i++) {
> + if (!(interrupt_status & (1 << i)))

BIT(), please!

Although, use __ffs() and this becomes redundant.

...

> +static void __mali_c55_power_off(struct mali_c55 *mali_c55)
> +{
> + reset_control_bulk_assert(ARRAY_SIZE(mali_c55->resets), mali_c55->resets);
> + clk_bulk_disable_unprepare(ARRAY_SIZE(mali_c55->clks), mali_c55->clks);
> +}
> +
> +static int mali_c55_runtime_suspend(struct device *dev)
> +{
> + struct mali_c55 *mali_c55 = dev_get_drvdata(dev);
> +
> + free_irq(mali_c55->irqnum, dev);

Do you really free the IRQ on device suspend? The law probably doesn't
forbid that though.

> + __mali_c55_power_off(mali_c55);
> +
> + return 0;
> +}
> +
> +static int __mali_c55_power_on(struct mali_c55 *mali_c55)
> +{
> + int ret;
> + u32 val;
> +
> + ret = clk_bulk_prepare_enable(ARRAY_SIZE(mali_c55->clks),
> + mali_c55->clks);
> + if (ret) {
> + dev_err(mali_c55->dev, "failed to enable clocks\n");
> + return ret;
> + }
> +
> + ret = reset_control_bulk_deassert(ARRAY_SIZE(mali_c55->resets),
> + mali_c55->resets);
> + if (ret) {
> + dev_err(mali_c55->dev, "failed to deassert resets\n");
> + return ret;
> + }
> +
> + /* Use "software only" context management. */
> + mali_c55_update_bits(mali_c55, MALI_C55_REG_MCU_CONFIG,
> + MALI_C55_REG_MCU_CONFIG_OVERRIDE_MASK, 0x01);
> +
> + /*
> + * Mask the interrupts and clear any that were set, then unmask the ones
> + * that we actually want to handle.
> + */
> + mali_c55_write(mali_c55, MALI_C55_REG_INTERRUPT_MASK_VECTOR,
> + MALI_C55_INTERRUPT_MASK_ALL);
> + mali_c55_write(mali_c55, MALI_C55_REG_INTERRUPT_CLEAR_VECTOR,
> + MALI_C55_INTERRUPT_MASK_ALL);
> + mali_c55_write(mali_c55, MALI_C55_REG_INTERRUPT_CLEAR, 0x01);
> + mali_c55_write(mali_c55, MALI_C55_REG_INTERRUPT_CLEAR, 0x00);
> +
> + mali_c55_update_bits(mali_c55, MALI_C55_REG_INTERRUPT_MASK_VECTOR,
> + MALI_C55_INTERRUPT_BIT(MALI_C55_IRQ_ISP_START) |
> + MALI_C55_INTERRUPT_BIT(MALI_C55_IRQ_ISP_DONE) |
> + MALI_C55_INTERRUPT_BIT(MALI_C55_IRQ_FR_Y_DONE) |
> + MALI_C55_INTERRUPT_BIT(MALI_C55_IRQ_FR_UV_DONE) |
> + MALI_C55_INTERRUPT_BIT(MALI_C55_IRQ_DS_Y_DONE) |
> + MALI_C55_INTERRUPT_BIT(MALI_C55_IRQ_DS_UV_DONE),
> + 0x00);
> +
> + /* Set safe stop to ensure we're in a non-streaming state */
> + mali_c55_write(mali_c55, MALI_C55_REG_INPUT_MODE_REQUEST,
> + MALI_C55_INPUT_SAFE_STOP);
> + readl_poll_timeout(mali_c55->base + MALI_C55_REG_MODE_STATUS,
> + val, !val, 10 * USEC_PER_MSEC, 250 * USEC_PER_MSEC);
> +
> + return 0;
> +}
> +
> +static int mali_c55_runtime_resume(struct device *dev)
> +{
> + struct mali_c55 *mali_c55 = dev_get_drvdata(dev);
> + int ret;
> +
> + ret = __mali_c55_power_on(mali_c55);
> + if (ret)
> + return ret;
> +
> + /*
> + * The driver needs to transfer large amounts of register settings to
> + * the ISP each frame, using either a DMA transfer or memcpy. We use a
> + * threaded IRQ to avoid disabling interrupts the entire time that's
> + * happening.
> + */
> + ret = request_threaded_irq(mali_c55->irqnum, NULL, mali_c55_isr,
> + IRQF_ONESHOT, dev_driver_string(dev), dev);
> + if (ret) {
> + __mali_c55_power_off(mali_c55);
> + dev_err(dev, "failed to request irq\n");
> + }
> +
> + return ret;
> +}
> +
> +static const struct dev_pm_ops mali_c55_pm_ops = {
> + SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> + pm_runtime_force_resume)
> + SET_RUNTIME_PM_OPS(mali_c55_runtime_suspend, mali_c55_runtime_resume,
> + NULL)
> +};
> +
> +static int mali_c55_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct mali_c55 *mali_c55;
> + struct resource *res;
> + dma_cap_mask_t mask;
> + int ret;
> +
> + mali_c55 = devm_kzalloc(dev, sizeof(*mali_c55), GFP_KERNEL);
> + if (!mali_c55)
> + return -ENOMEM;
> +
> + mali_c55->dev = dev;
> + platform_set_drvdata(pdev, mali_c55);
> +
> + mali_c55->base = devm_platform_get_and_ioremap_resource(pdev, 0,
> + &res);
> + if (IS_ERR(mali_c55->base))
> + return dev_err_probe(dev, PTR_ERR(mali_c55->base),
> + "failed to map IO memory\n");
> +
> + for (unsigned int i = 0; i < ARRAY_SIZE(mali_c55_clk_names); i++)
> + mali_c55->clks[i].id = mali_c55_clk_names[i];
> +
> + ret = devm_clk_bulk_get(dev, ARRAY_SIZE(mali_c55->clks), mali_c55->clks);
> + if (ret)
> + return dev_err_probe(dev, ret, "failed to acquire clocks\n");
> +
> + for (unsigned int i = 0; i < ARRAY_SIZE(mali_c55_reset_names); i++)
> + mali_c55->resets[i].id = mali_c55_reset_names[i];
> +
> + ret = devm_reset_control_bulk_get_optional_shared(
> + dev, ARRAY_SIZE(mali_c55_reset_names), mali_c55->resets);
> + if (ret)
> + return dev_err_probe(dev, ret, "failed to acquire resets\n");
> +
> + of_reserved_mem_device_init(dev);
> + vb2_dma_contig_set_max_seg_size(dev, UINT_MAX);
> +
> + dma_cap_zero(mask);
> + dma_cap_set(DMA_MEMCPY, mask);
> +
> + ret = __mali_c55_power_on(mali_c55);
> + if (ret)
> + return dev_err_probe(dev, ret, "failed to power on\n");
> +
> + ret = mali_c55_check_hwcfg(mali_c55);
> + if (ret)
> + goto err_power_off;
> +
> + /*
> + * No failure here because we will just fallback on memcpy if there is
> + * no usable DMA channel on the system.
> + */
> + mali_c55->channel = dma_request_channel(mask, NULL, NULL);
> + dev_dbg(mali_c55->dev,
> + "No DMA channel for config, falling back to memcpy\n");
> +
> + ret = mali_c55_init_context(mali_c55, res);
> + if (ret)
> + goto err_release_dma_channel;
> +
> + mali_c55->media_dev.dev = dev;
> +
> + mali_c55->inline_mode = device_property_read_bool(dev, "arm,inline_mode");
> +
> + ret = mali_c55_media_frameworks_init(mali_c55);
> + if (ret)
> + goto err_free_context_registers;
> +
> + __mali_c55_power_off(mali_c55);
> +
> + pm_runtime_set_autosuspend_delay(&pdev->dev, 2000);
> + pm_runtime_use_autosuspend(&pdev->dev);
> + pm_runtime_enable(&pdev->dev);

Note that runtime PM resume fails before this so accessing UAPI would
fail. Please enable runtime PM before registering anything outside the
driver.

> +
> + mali_c55->irqnum = platform_get_irq(pdev, 0);

Wouldn't it make sense to read this earlier? For the same reason than
above, actually.

> + if (mali_c55->irqnum < 0) {
> + dev_err(dev, "failed to get interrupt\n");
> + goto err_pm_runtime_disable;
> + }
> +
> + return 0;
> +
> +err_pm_runtime_disable:
> + pm_runtime_disable(&pdev->dev);
> + mali_c55_media_frameworks_deinit(mali_c55);
> +err_free_context_registers:
> + kfree(mali_c55->context.registers);
> +err_release_dma_channel:
> + if (mali_c55->channel)
> + dma_release_channel(mali_c55->channel);
> +err_power_off:
> + __mali_c55_power_off(mali_c55);
> +
> + return ret;
> +}
> +

...

> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-isp.c b/drivers/media/platform/arm/mali-c55/mali-c55-isp.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..20d4d16c75fbf0d5519ecadb5ed1d080bdae05de
> --- /dev/null
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-isp.c
> @@ -0,0 +1,656 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ARM Mali-C55 ISP Driver - Image signal processor
> + *
> + * Copyright (C) 2024 Ideas on Board Oy

It's 2025 already.

> + */
> +
> +#include <linux/delay.h>
> +#include <linux/iopoll.h>
> +#include <linux/property.h>
> +#include <linux/string.h>
> +
> +#include <linux/media/arm/mali-c55-config.h>

If this is a UAPI header, please include uapi in the path, too.

Earlier such headers have been under include/uapi/linux, I don't object
putting new ones elsewhere in principle though. Just check with Hans and
Laurent, too... I don't have an opinion yet really.

> +/* NOT const because the default needs to be filled in at runtime */
> +static struct v4l2_ctrl_config mali_c55_isp_v4l2_custom_ctrls[] = {
> + {
> + .ops = &mali_c55_isp_ctrl_ops,
> + .id = V4L2_CID_MALI_C55_CAPABILITIES,
> + .name = "Mali-C55 ISP Capabilities",
> + .type = V4L2_CTRL_TYPE_BITMASK,
> + .min = 0,
> + .max = MALI_C55_GPS_PONG_FITTED |
> + MALI_C55_GPS_WDR_FITTED |
> + MALI_C55_GPS_COMPRESSION_FITTED |
> + MALI_C55_GPS_TEMPER_FITTED |
> + MALI_C55_GPS_SINTER_LITE_FITTED |
> + MALI_C55_GPS_SINTER_FITTED |
> + MALI_C55_GPS_IRIDIX_LTM_FITTED |
> + MALI_C55_GPS_IRIDIX_GTM_FITTED |
> + MALI_C55_GPS_CNR_FITTED |
> + MALI_C55_GPS_FRSCALER_FITTED |
> + MALI_C55_GPS_DS_PIPE_FITTED,
> + .def = 0,
> + },
> +};
> +
> +static int mali_c55_isp_init_controls(struct mali_c55 *mali_c55)
> +{
> + struct v4l2_ctrl_handler *handler = &mali_c55->isp.handler;
> + struct v4l2_ctrl *capabilities;
> + int ret;
> +
> + ret = v4l2_ctrl_handler_init(handler, 1);
> + if (ret)
> + return ret;
> +
> + mali_c55_isp_v4l2_custom_ctrls[0].def = mali_c55->capabilities;

The capabilities here are still specific to a device, not global, in
principle at least. Can you move it here, as a local variable?

> +
> + capabilities = v4l2_ctrl_new_custom(handler,
> + &mali_c55_isp_v4l2_custom_ctrls[0],
> + NULL);
> + if (capabilities)
> + capabilities->flags |= V4L2_CTRL_FLAG_READ_ONLY;
> +
> + if (handler->error) {
> + dev_err(mali_c55->dev, "failed to register capabilities control\n");
> + v4l2_ctrl_handler_free(handler);
> + return handler->error;

v4l2_ctrl_handler_free() will return the error soon, presumably sooner
than the above code makes it to upstream. Before that, this pattern
won't work as v4l2_ctrl_handler_free() also resets the handler's error
field. :-)

> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-registers.h b/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
> new file mode 100644
> index 0000000000000000000000000000000000000000..36a81be0191a15da91809dd2da5d279716f6d725
> --- /dev/null
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-registers.h
> @@ -0,0 +1,318 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * ARM Mali-C55 ISP Driver - Register definitions
> + *
> + * Copyright (C) 2024 Ideas on Board Oy
> + */
> +
> +#ifndef _MALI_C55_REGISTERS_H
> +#define _MALI_C55_REGISTERS_H
> +
> +#include <linux/bits.h>
> +
> +/* ISP Common 0x00000 - 0x000ff */
> +
> +#define MALI_C55_REG_API 0x00000
> +#define MALI_C55_REG_PRODUCT 0x00004
> +#define MALI_C55_REG_VERSION 0x00008
> +#define MALI_C55_REG_REVISION 0x0000c
> +#define MALI_C55_REG_PULSE_MODE 0x0003c
> +#define MALI_C55_REG_INPUT_MODE_REQUEST 0x0009c
> +#define MALI_C55_INPUT_SAFE_STOP 0x00
> +#define MALI_C55_INPUT_SAFE_START 0x01
> +#define MALI_C55_REG_MODE_STATUS 0x000a0
> +#define MALI_C55_REG_INTERRUPT_MASK_VECTOR 0x00030
> +#define MALI_C55_INTERRUPT_MASK_ALL GENMASK(31, 0)
> +
> +#define MALI_C55_REG_GLOBAL_MONITOR 0x00050
> +
> +#define MALI_C55_REG_GEN_VIDEO 0x00080
> +#define MALI_C55_REG_GEN_VIDEO_ON_MASK BIT(0)
> +#define MALI_C55_REG_GEN_VIDEO_MULTI_MASK BIT(1)
> +#define MALI_C55_REG_GEN_PREFETCH_MASK GENMASK(31, 16)
> +
> +#define MALI_C55_REG_MCU_CONFIG 0x00020
> +#define MALI_C55_REG_MCU_CONFIG_OVERRIDE_MASK BIT(0)
> +#define MALI_C55_REG_MCU_CONFIG_WRITE_MASK BIT(1)
> +#define MALI_C55_MCU_CONFIG_WRITE(x) ((x) << 1)

Is x unsigned?

> +#define MALI_C55_REG_MCU_CONFIG_WRITE_PING BIT(1)
> +#define MALI_C55_REG_MCU_CONFIG_WRITE_PONG 0x00
> +#define MALI_C55_REG_MULTI_CONTEXT_MODE_MASK BIT(8)
> +#define MALI_C55_REG_PING_PONG_READ 0x00024
> +#define MALI_C55_REG_PING_PONG_READ_MASK BIT(2)
> +#define MALI_C55_INTERRUPT_BIT(x) BIT(x)
> +
> +#define MALI_C55_REG_GLOBAL_PARAMETER_STATUS 0x00068
> +#define MALI_C55_GPS_PONG_FITTED BIT(0)
> +#define MALI_C55_GPS_WDR_FITTED BIT(1)
> +#define MALI_C55_GPS_COMPRESSION_FITTED BIT(2)
> +#define MALI_C55_GPS_TEMPER_FITTED BIT(3)
> +#define MALI_C55_GPS_SINTER_LITE_FITTED BIT(4)
> +#define MALI_C55_GPS_SINTER_FITTED BIT(5)
> +#define MALI_C55_GPS_IRIDIX_LTM_FITTED BIT(6)
> +#define MALI_C55_GPS_IRIDIX_GTM_FITTED BIT(7)
> +#define MALI_C55_GPS_CNR_FITTED BIT(8)
> +#define MALI_C55_GPS_FRSCALER_FITTED BIT(9)
> +#define MALI_C55_GPS_DS_PIPE_FITTED BIT(10)
> +
> +#define MALI_C55_REG_BLANKING 0x00084
> +#define MALI_C55_REG_HBLANK_MASK GENMASK(15, 0)
> +#define MALI_C55_REG_VBLANK_MASK GENMASK(31, 16)
> +#define MALI_C55_VBLANK(x) ((x) << 16)

Same question for the bit shifts left elsewhere in the header.

> +
> +#define MALI_C55_REG_HC_START 0x00088
> +#define MALI_C55_HC_START(h) (((h) & 0xffff) << 16)
> +#define MALI_C55_REG_HC_SIZE 0x0008c
> +#define MALI_C55_HC_SIZE(h) ((h) & 0xffff)
> +#define MALI_C55_REG_VC_START_SIZE 0x00094
> +#define MALI_C55_VC_START(v) ((v) & 0xffff)
> +#define MALI_C55_VC_SIZE(v) (((v) & 0xffff) << 16)
> +
> +/* Ping/Pong Configuration Space */
> +#define MALI_C55_REG_BASE_ADDR 0x18e88
> +#define MALI_C55_REG_BYPASS_0 0x18eac
> +#define MALI_C55_REG_BYPASS_0_VIDEO_TEST BIT(0)
> +#define MALI_C55_REG_BYPASS_0_INPUT_FMT BIT(1)
> +#define MALI_C55_REG_BYPASS_0_DECOMPANDER BIT(2)
> +#define MALI_C55_REG_BYPASS_0_SENSOR_OFFSET_WDR BIT(3)
> +#define MALI_C55_REG_BYPASS_0_GAIN_WDR BIT(4)
> +#define MALI_C55_REG_BYPASS_0_FRAME_STITCH BIT(5)
> +#define MALI_C55_REG_BYPASS_1 0x18eb0
> +#define MALI_C55_REG_BYPASS_1_DIGI_GAIN BIT(0)
> +#define MALI_C55_REG_BYPASS_1_FE_SENSOR_OFFS BIT(1)
> +#define MALI_C55_REG_BYPASS_1_FE_SQRT BIT(2)
> +#define MALI_C55_REG_BYPASS_1_RAW_FE BIT(3)
> +#define MALI_C55_REG_BYPASS_2 0x18eb8
> +#define MALI_C55_REG_BYPASS_2_SINTER BIT(0)
> +#define MALI_C55_REG_BYPASS_2_TEMPER BIT(1)
> +#define MALI_C55_REG_BYPASS_3 0x18ebc
> +#define MALI_C55_REG_BYPASS_3_SQUARE_BE BIT(0)
> +#define MALI_C55_REG_BYPASS_3_SENSOR_OFFSET_PRE_SH BIT(1)
> +#define MALI_C55_REG_BYPASS_3_MESH_SHADING BIT(3)
> +#define MALI_C55_REG_BYPASS_3_WHITE_BALANCE BIT(4)
> +#define MALI_C55_REG_BYPASS_3_IRIDIX BIT(5)
> +#define MALI_C55_REG_BYPASS_3_IRIDIX_GAIN BIT(6)
> +#define MALI_C55_REG_BYPASS_4 0x18ec0
> +#define MALI_C55_REG_BYPASS_4_DEMOSAIC_RGB BIT(1)
> +#define MALI_C55_REG_BYPASS_4_PF_CORRECTION BIT(3)
> +#define MALI_C55_REG_BYPASS_4_CCM BIT(4)
> +#define MALI_C55_REG_BYPASS_4_CNR BIT(5)
> +#define MALI_C55_REG_FR_BYPASS 0x18ec4
> +#define MALI_C55_REG_DS_BYPASS 0x18ec8
> +#define MALI_C55_BYPASS_CROP BIT(0)
> +#define MALI_C55_BYPASS_SCALER BIT(1)
> +#define MALI_C55_BYPASS_GAMMA_RGB BIT(2)
> +#define MALI_C55_BYPASS_SHARPEN BIT(3)
> +#define MALI_C55_BYPASS_CS_CONV BIT(4)
> +#define MALI_C55_REG_ISP_RAW_BYPASS 0x18ecc
> +#define MALI_C55_ISP_RAW_BYPASS_BYPASS_MASK BIT(0)
> +#define MALI_C55_ISP_RAW_BYPASS_FR_BYPASS_MASK GENMASK(9, 8)
> +#define MALI_C55_ISP_RAW_BYPASS_RAW_FR_BYPASS (2 << 8)
> +#define MALI_C55_ISP_RAW_BYPASS_RGB_FR_BYPASS (1 << 8)

BIT() or make these unsigned.

...

> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-resizer.c b/drivers/media/platform/arm/mali-c55/mali-c55-resizer.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..f0b079a2322125ad6313d6cf9651afaf2180b96c
> --- /dev/null
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-resizer.c

...

> +static unsigned int mali_c55_rsz_calculate_bank(struct mali_c55 *mali_c55,
> + unsigned int rsz_in,
> + unsigned int rsz_out)
> +{
> + unsigned int rsz_ratio = (rsz_out * 1000U) / rsz_in;

Can this overflow?

> + unsigned int i;
> +
> + for (i = 0; i < ARRAY_SIZE(mali_c55_rsz_coef_banks_range_start); i++)
> + if (rsz_ratio >= mali_c55_rsz_coef_banks_range_start[i])
> + break;
> +
> + return i;
> +}

...

> +static int mali_c55_rsz_set_sink_fmt(struct v4l2_subdev *sd,
> + struct v4l2_subdev_state *state,
> + struct v4l2_subdev_format *format)
> +{
> + struct v4l2_mbus_framefmt *fmt = &format->format;
> + struct v4l2_mbus_framefmt *sink_fmt;
> + unsigned int active_sink;
> + struct v4l2_rect *rect;
> +
> + sink_fmt = v4l2_subdev_state_get_format(state, format->pad, 0);
> +
> + /*
> + * Clamp to min/max and then reset crop and compose rectangles to the
> + * newly applied size.
> + */
> + sink_fmt->width = clamp_t(unsigned int, fmt->width,
> + MALI_C55_MIN_WIDTH, MALI_C55_MAX_WIDTH);
> + sink_fmt->height = clamp_t(unsigned int, fmt->height,
> + MALI_C55_MIN_HEIGHT, MALI_C55_MAX_HEIGHT);
> +
> + /*
> + * Make sure the media bus code for the bypass pad is one of the
> + * supported ISP input media bus codes. Default it to SRGGB otherwise.
> + */
> + if (format->pad == MALI_C55_RSZ_SINK_BYPASS_PAD)
> + sink_fmt->code = mali_c55_isp_get_mbus_config_by_code(fmt->code) ?
> + fmt->code : MEDIA_BUS_FMT_SRGGB20_1X20;
> +
> + *fmt = *sink_fmt;
> +
> + if (format->pad == MALI_C55_RSZ_SINK_PAD) {
> + rect = v4l2_subdev_state_get_crop(state, format->pad);
> + rect->left = 0;
> + rect->top = 0;
> + rect->width = fmt->width;
> + rect->height = fmt->height;
> +
> + rect = v4l2_subdev_state_get_compose(state, format->pad);
> + rect->left = 0;
> + rect->top = 0;
> + rect->width = fmt->width;
> + rect->height = fmt->height;

If both of the rects are the same, you can simply assign the former to
the latter.

Overall, this seems like a nicely written driver. It's a very big one,
too...

--
Kind regards,

Sakari Ailus