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Date:   Wed, 4 Oct 2023 18:42:47 +0530
From:   Vinod Koul <vkoul@kernel.org>
To:     Martin =?utf-8?Q?Povi=C5=A1er?= <povik+lin@cutebit.org>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>, asahi@lists.linux.dev,
        dmaengine@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] dmaengine: apple-sio: Add Apple SIO driver
Message-ID: <ZR1kz7Sil8onc1uC@matsya>
References: <20230828170013.75820-1-povik+lin@cutebit.org>
 <20230828170013.75820-3-povik+lin@cutebit.org>
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In-Reply-To: <20230828170013.75820-3-povik+lin@cutebit.org>
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On 28-08-23, 19:00, Martin Povišer wrote:
> Add a dmaengine driver for the Apple SIO coprocessor found on Apple
> SoCs where it provides DMA services. Have the driver support cyclic
> transactions so that ALSA drivers can rely on it in audio output to
> HDMI and DisplayPort.
> 
> Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
> ---
>  MAINTAINERS             |   2 +
>  drivers/dma/Kconfig     |  11 +
>  drivers/dma/Makefile    |   1 +
>  drivers/dma/apple-sio.c | 868 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 882 insertions(+)
>  create mode 100644 drivers/dma/apple-sio.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3be1bdfe8ecc..e65cf3d535ef 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1865,7 +1865,9 @@ M:	Martin Povišer <povik+lin@cutebit.org>
>  L:	asahi@lists.linux.dev
>  L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
>  S:	Maintained
> +F:	Documentation/devicetree/bindings/dma/apple,sio.yaml
>  F:	Documentation/devicetree/bindings/sound/apple,*
> +F:	drivers/dma/apple-sio.c
>  F:	sound/soc/apple/*
>  F:	sound/soc/codecs/cs42l83-i2c.c
>  
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index f52d36e713f3..6e385dee2d3d 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -89,10 +89,21 @@ config APPLE_ADMAC
>  	tristate "Apple ADMAC support"
>  	depends on ARCH_APPLE || COMPILE_TEST
>  	select DMA_ENGINE
> +	select DMA_VIRTUAL_CHANNELS
>  	default ARCH_APPLE
>  	help
>  	  Enable support for Audio DMA Controller found on Apple Silicon SoCs.
>  
> +config APPLE_SIO
> +	tristate "Apple SIO support"
> +	depends on ARCH_APPLE || COMPILE_TEST
> +	depends on APPLE_RTKIT
> +	select DMA_ENGINE
> +	default ARCH_APPLE
> +	help
> +	  Enable support for the SIO coprocessor found on Apple Silicon SoCs
> +	  where it provides DMA services.
> +
>  config AT_HDMAC
>  	tristate "Atmel AHB DMA support"
>  	depends on ARCH_AT91
> diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
> index 83553a97a010..787583ff2d45 100644
> --- a/drivers/dma/Makefile
> +++ b/drivers/dma/Makefile
> @@ -18,6 +18,7 @@ obj-$(CONFIG_AMBA_PL08X) += amba-pl08x.o
>  obj-$(CONFIG_AMCC_PPC440SPE_ADMA) += ppc4xx/
>  obj-$(CONFIG_AMD_PTDMA) += ptdma/
>  obj-$(CONFIG_APPLE_ADMAC) += apple-admac.o
> +obj-$(CONFIG_APPLE_SIO) += apple-sio.o
>  obj-$(CONFIG_AT_HDMAC) += at_hdmac.o
>  obj-$(CONFIG_AT_XDMAC) += at_xdmac.o
>  obj-$(CONFIG_AXI_DMAC) += dma-axi-dmac.o
> diff --git a/drivers/dma/apple-sio.c b/drivers/dma/apple-sio.c
> new file mode 100644
> index 000000000000..e15deeded4dc
> --- /dev/null
> +++ b/drivers/dma/apple-sio.c
> @@ -0,0 +1,868 @@
> +// SPDX-License-Identifier: GPL-2.0-only OR MIT
> +/*
> + * Driver for SIO coprocessor on t8103 (M1) and other Apple SoCs
> + *
> + * Copyright (C) The Asahi Linux Contributors
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/completion.h>
> +#include <linux/device.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_dma.h>
> +#include <linux/soc/apple/rtkit.h>
> +
> +#include "dmaengine.h"
> +#include "virt-dma.h"
> +
> +#define NCHANNELS_MAX	0x80
> +
> +#define REG_CPU_CONTROL	0x44
> +#define CPU_CONTROL_RUN BIT(4)
> +
> +#define SIOMSG_DATA	GENMASK(63, 32)
> +#define SIOMSG_TYPE	GENMASK(23, 16)
> +#define SIOMSG_PARAM	GENMASK(31, 24)
> +#define SIOMSG_TAG	GENMASK(13, 8)
> +#define SIOMSG_EP	GENMASK(7, 0)
> +
> +#define EP_SIO		0x20
> +
> +#define MSG_START	0x2
> +#define MSG_SETUP	0x3
> +#define MSG_CONFIGURE	0x5
> +#define MSG_ISSUE	0x6
> +#define MSG_TERMINATE	0x8
> +#define MSG_ACK		0x65
> +#define MSG_NACK	0x66
> +#define MSG_STARTED	0x67
> +#define MSG_REPORT	0x68
> +
> +#define SIO_CALL_TIMEOUT_MS	100
> +#define SIO_SHMEM_SIZE		0x1000
> +#define SIO_NO_DESC_SLOTS	64
> +
> +/*
> + * There are two kinds of 'transaction descriptors' in play here.
> + *
> + * There's the struct sio_tx, and the struct dma_async_tx_descriptor embedded
> + * inside, which jointly represent a transaction to the dmaengine subsystem.
> + * At this time we only support those transactions to be cyclic.
> + *
> + * Then there are the coprocessor descriptors, which is what the coprocessor
> + * knows and understands. These don't seem to have a cyclic regime, so we can't
> + * map the dmaengine transaction on an exact coprocessor counterpart. Instead
> + * we continually queue up many coprocessor descriptors to implement a cyclic
> + * transaction.
> + *
> + * The number below is the maximum of how far ahead (how many) coprocessor
> + * descriptors we should be queuing up, per channel, for a cyclic transaction.
> + * Basically it's a made-up number.
> + */
> +#define SIO_MAX_NINFLIGHT	4

you meant SIO_MAX_INFLIGHT if not what is NINFLIGHT?

> +struct sio_coproc_desc {
> +	u32 pad1;
> +	u32 flag;
> +	u64 unk;
> +	u64 iova;
> +	u64 size;
> +	u64 pad2;
> +	u64 pad3;
> +} __packed;
> +static_assert(sizeof(struct sio_coproc_desc) == 48);
> +
> +struct sio_shmem_chan_config {
> +	u32 datashape;
> +	u32 timeout;
> +	u32 fifo;
> +	u32 threshold;
> +	u32 limit;
> +} __packed;
> +
> +struct sio_data;
> +struct sio_tx;
> +
> +struct sio_chan {
> +	unsigned int no;
> +	struct sio_data *host;
> +	struct virt_dma_chan vc;
> +	struct work_struct terminate_wq;
> +
> +	struct sio_tx *current_tx;
> +};
> +
> +#define SIO_NTAGS		16
> +
> +typedef void (*sio_ack_callback)(struct sio_chan *, void *, bool);

what is this callback used for?


> +
> +struct sio_data {
> +	void __iomem *base;
> +	struct dma_device dma;
> +	struct device *dev;
> +	struct apple_rtkit *rtk;
> +	void *shmem;
> +	struct sio_coproc_desc *shmem_desc_base;
> +	unsigned long *desc_allocated;
> +
> +	struct sio_tagdata {
> +		DECLARE_BITMAP(allocated, SIO_NTAGS);
> +		int last_tag;
> +
> +		struct completion completions[SIO_NTAGS];
> +		bool atomic[SIO_NTAGS];
> +		bool acked[SIO_NTAGS];
> +
> +		sio_ack_callback ack_callback[SIO_NTAGS];
> +		void *cookie[SIO_NTAGS];
> +	} tags;
> +
> +	int nchannels;
> +	struct sio_chan channels[];
> +};
> +
> +struct sio_tx {
> +	struct virt_dma_desc vd;
> +	struct completion done;
> +
> +	bool terminated;
> +	size_t period_len;
> +	int nperiods;
> +	int ninflight;
> +	int next;
> +
> +	struct sio_coproc_desc *siodesc[];
> +};
> +
> +static int sio_send_siomsg(struct sio_data *sio, u64 msg);
> +static int sio_send_siomsg_atomic(struct sio_data *sio, u64 msg,
> +				  sio_ack_callback ack_callback,
> +				  void *cookie);
> +static int sio_call(struct sio_data *sio, u64 msg);
> +
> +static struct sio_chan *to_sio_chan(struct dma_chan *chan)
> +{
> +	return container_of(chan, struct sio_chan, vc.chan);
> +}
> +
> +static struct sio_tx *to_sio_tx(struct dma_async_tx_descriptor *tx)
> +{
> +	return container_of(tx, struct sio_tx, vd.tx);
> +}
> +
> +static int sio_alloc_tag(struct sio_data *sio)
> +{
> +	struct sio_tagdata *tags = &sio->tags;
> +	int tag, i;
> +
> +	/*
> +	 * Because tag number 0 is special, the usable tag range
> +	 * is 1...(SIO_NTAGS - 1). So, to pick the next usable tag,
> +	 * we do modulo (SIO_NTAGS - 1) *then* plus one.
> +	 */
> +
> +#define SIO_USABLE_TAGS (SIO_NTAGS - 1)
> +	tag = (READ_ONCE(tags->last_tag) % SIO_USABLE_TAGS) + 1;
> +
> +	for (i = 0; i < SIO_USABLE_TAGS; i++) {
> +		if (!test_and_set_bit(tag, tags->allocated))
> +			break;
> +
> +		tag = (tag % SIO_USABLE_TAGS) + 1;
> +	}
> +
> +	WRITE_ONCE(tags->last_tag, tag);
> +
> +	if (i < SIO_USABLE_TAGS)
> +		return tag;
> +	else
> +		return -EBUSY;
> +#undef SIO_USABLE_TAGS

ida_alloc can be used as well to get a tag as well

> +}
> +
> +static void sio_free_tag(struct sio_data *sio, int tag)
> +{
> +	struct sio_tagdata *tags = &sio->tags;
> +
> +	if (WARN_ON(tag >= SIO_NTAGS))
> +		return;
> +
> +	tags->atomic[tag] = false;
> +	tags->ack_callback[tag] = NULL;
> +
> +	WARN_ON(!test_and_clear_bit(tag, tags->allocated));
> +}
> +
> +static void sio_set_tag_atomic(struct sio_data *sio, int tag,
> +			       sio_ack_callback ack_callback,
> +			       void *cookie)
> +{
> +	struct sio_tagdata *tags = &sio->tags;
> +
> +	tags->atomic[tag] = true;
> +	tags->ack_callback[tag] = ack_callback;
> +	tags->cookie[tag] = cookie;
> +}
> +
> +static struct sio_coproc_desc *sio_alloc_desc(struct sio_data *sio)
> +{
> +	int i;
> +
> +	for (i = 0; i < SIO_NO_DESC_SLOTS; i++)
> +		if (!test_and_set_bit(i, sio->desc_allocated))
> +			return sio->shmem_desc_base + i;
> +
> +	return NULL;
> +}
> +
> +static void sio_free_desc(struct sio_data *sio, struct sio_coproc_desc *desc)
> +{
> +	clear_bit(desc - sio->shmem_desc_base, sio->desc_allocated);
> +}
> +
> +static int sio_coproc_desc_slot(struct sio_data *sio, struct sio_coproc_desc *desc)
> +{
> +	return (desc - sio->shmem_desc_base) * 4;
> +}
> +
> +static enum dma_transfer_direction sio_chan_direction(int channo)
> +{
> +	/* Channel directions are fixed based on channel number */
> +	return (channo & 1) ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
> +}
> +
> +static void sio_tx_free(struct virt_dma_desc *vd)
> +{
> +	struct sio_data *sio = to_sio_chan(vd->tx.chan)->host;
> +	struct sio_tx *siotx = to_sio_tx(&vd->tx);
> +	int i;
> +
> +	for (i = 0; i < siotx->nperiods; i++)
> +		if (siotx->siodesc[i])
> +			sio_free_desc(sio, siotx->siodesc[i]);
> +	kfree(siotx);
> +}
> +
> +static struct dma_async_tx_descriptor *sio_prep_dma_cyclic(
> +		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
> +		size_t period_len, enum dma_transfer_direction direction,
> +		unsigned long flags)
> +{
> +	struct sio_chan *siochan = to_sio_chan(chan);
> +	struct sio_tx *siotx = NULL;
> +	int i, nperiods = buf_len / period_len;
> +
> +	if (direction != sio_chan_direction(siochan->no))
> +		return NULL;
> +
> +	siotx = kzalloc(struct_size(siotx, siodesc, nperiods), GFP_NOWAIT);

wasnt there a helper to do this sort of thing...

> +	if (!siotx)
> +		return NULL;
> +
> +	init_completion(&siotx->done);
> +	siotx->period_len = period_len;
> +	siotx->nperiods = nperiods;
> +
> +	for (i = 0; i < nperiods; i++) {
> +		struct sio_coproc_desc *d;
> +
> +		siotx->siodesc[i] = d = sio_alloc_desc(siochan->host);
> +		if (!d) {
> +			sio_tx_free(&siotx->vd);
> +			return NULL;
> +		}
> +
> +		d->flag = 1; // not sure what's up with this

:-) but /* comments only */ pls

> +		d->iova = buf_addr + period_len * i;
> +		d->size = period_len;
> +	}
> +	dma_wmb();

why do you need a barrier here

> +
> +	return vchan_tx_prep(&siochan->vc, &siotx->vd, flags);
> +}
> +
> +static enum dma_status sio_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> +				     struct dma_tx_state *txstate)
> +{
> +	struct sio_chan *siochan = to_sio_chan(chan);
> +	struct virt_dma_desc *vd;
> +	struct sio_tx *siotx;
> +	enum dma_status ret;
> +	unsigned long flags;
> +	int periods_residue;
> +	size_t residue;
> +
> +	ret = dma_cookie_status(chan, cookie, txstate);
> +	if (ret == DMA_COMPLETE || !txstate)
> +		return ret;
> +
> +	spin_lock_irqsave(&siochan->vc.lock, flags);
> +	siotx = siochan->current_tx;
> +
> +	if (siotx && siotx->vd.tx.cookie == cookie) {
> +		ret = DMA_IN_PROGRESS;
> +		periods_residue = siotx->next - siotx->ninflight;
> +		while (periods_residue < 0)
> +			periods_residue += siotx->nperiods;
> +		residue = (siotx->nperiods - periods_residue) * siotx->period_len;
> +	} else {
> +		ret = DMA_IN_PROGRESS;
> +		residue = 0;
> +		vd = vchan_find_desc(&siochan->vc, cookie);
> +		if (vd) {
> +			siotx = to_sio_tx(&vd->tx);
> +			residue = siotx->period_len * siotx->nperiods;
> +		}
> +	}
> +	spin_unlock_irqrestore(&siochan->vc.lock, flags);
> +	dma_set_residue(txstate, residue);
> +
> +	return ret;
> +}
> +
> +static bool sio_fill_in_locked(struct sio_chan *siochan);
> +
> +static void sio_handle_issue_ack(struct sio_chan *siochan, void *cookie, bool ok)
> +{
> +	unsigned long flags;
> +	dma_cookie_t tx_cookie = (unsigned long) cookie;
> +	struct sio_tx *tx;

reverse christmas tree style pls
> +
> +	if (!ok) {
> +		dev_err(siochan->host->dev, "nacked issue on chan %d\n", siochan->no);
> +		return;
> +	}
> +
> +	spin_lock_irqsave(&siochan->vc.lock, flags);
> +	if (!siochan->current_tx || tx_cookie != siochan->current_tx->vd.tx.cookie ||
> +			siochan->current_tx->terminated)
> +		goto out;
> +
> +	tx = siochan->current_tx;
> +	tx->next = (tx->next + 1) % tx->nperiods;
> +	tx->ninflight++;
> +	sio_fill_in_locked(siochan);
> +
> +out:
> +	spin_unlock_irqrestore(&siochan->vc.lock, flags);
> +}
> +
> +static bool sio_fill_in_locked(struct sio_chan *siochan)
> +{
> +	struct sio_data *sio = siochan->host;
> +	struct sio_tx *tx = siochan->current_tx;
> +	struct sio_coproc_desc *d = tx->siodesc[tx->next];
> +	int ret;
> +
> +	if (tx->ninflight >= SIO_MAX_NINFLIGHT || tx->terminated)
> +		return false;
> +
> +	static_assert(sizeof(dma_cookie_t) <= sizeof(void *));
> +	ret = sio_send_siomsg_atomic(sio, FIELD_PREP(SIOMSG_EP, siochan->no) |
> +				     FIELD_PREP(SIOMSG_TYPE, MSG_ISSUE) |
> +				     FIELD_PREP(SIOMSG_DATA, sio_coproc_desc_slot(sio, d)),
> +				     sio_handle_issue_ack, (void *) (uintptr_t) tx->vd.tx.cookie);
> +	if (ret < 0)
> +		dev_err_ratelimited(sio->dev, "can't issue on chan %d ninflight %d: %d\n",
> +				    siochan->no, tx->ninflight, ret);
> +	return true;
> +}
> +
> +static void sio_update_current_tx_locked(struct sio_chan *siochan)
> +{
> +	struct virt_dma_desc *vd = vchan_next_desc(&siochan->vc);
> +
> +	if (vd && !siochan->current_tx) {
> +		list_del(&vd->node);
> +		siochan->current_tx = to_sio_tx(&vd->tx);
> +		sio_fill_in_locked(siochan);
> +	}
> +}
> +
> +static void sio_issue_pending(struct dma_chan *chan)
> +{
> +	struct sio_chan *siochan = to_sio_chan(chan);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&siochan->vc.lock, flags);
> +	vchan_issue_pending(&siochan->vc);
> +	sio_update_current_tx_locked(siochan);
> +	spin_unlock_irqrestore(&siochan->vc.lock, flags);
> +}
> +
> +static int sio_terminate_all(struct dma_chan *chan)
> +{
> +	struct sio_chan *siochan = to_sio_chan(chan);
> +	unsigned long flags;
> +	LIST_HEAD(to_free);
> +
> +	spin_lock_irqsave(&siochan->vc.lock, flags);
> +	if (siochan->current_tx && !siochan->current_tx->terminated) {
> +		dma_cookie_complete(&siochan->current_tx->vd.tx);
> +		siochan->current_tx->terminated = true;
> +		schedule_work(&siochan->terminate_wq);
> +	}
> +	vchan_get_all_descriptors(&siochan->vc, &to_free);
> +	spin_unlock_irqrestore(&siochan->vc.lock, flags);
> +
> +	vchan_dma_desc_free_list(&siochan->vc, &to_free);
> +
> +	return 0;
> +}
> +
> +static void sio_terminate_work(struct work_struct *wq)
> +{
> +	struct sio_chan *siochan = container_of(wq, struct sio_chan, terminate_wq);
> +	struct sio_tx *tx;
> +	unsigned long flags;
> +	int ret;
> +
> +	spin_lock_irqsave(&siochan->vc.lock, flags);
> +	tx = siochan->current_tx;
> +	spin_unlock_irqrestore(&siochan->vc.lock, flags);
> +
> +	if (WARN_ON(!tx))
> +		return;
> +
> +	ret = sio_call(siochan->host, FIELD_PREP(SIOMSG_EP, siochan->no) |
> +				      FIELD_PREP(SIOMSG_TYPE, MSG_TERMINATE));
> +	if (ret < 0)
> +		dev_err(siochan->host->dev, "terminate call on chan %d failed: %d\n",
> +			siochan->no, ret);
> +
> +	ret = wait_for_completion_timeout(&tx->done, msecs_to_jiffies(500));
> +	if (!ret)
> +		dev_err(siochan->host->dev, "terminate descriptor wait timed out\n");
> +
> +	tasklet_kill(&siochan->vc.task);
> +
> +	spin_lock_irqsave(&siochan->vc.lock, flags);
> +	WARN_ON(siochan->current_tx != tx);
> +	siochan->current_tx = NULL;
> +	sio_update_current_tx_locked(siochan);
> +	spin_unlock_irqrestore(&siochan->vc.lock, flags);
> +
> +	sio_tx_free(&tx->vd);
> +}
> +
> +static void sio_synchronize(struct dma_chan *chan)
> +{
> +	struct sio_chan *siochan = to_sio_chan(chan);
> +
> +	flush_work(&siochan->terminate_wq);
> +}
> +
> +static void sio_free_chan_resources(struct dma_chan *chan)
> +{
> +	sio_terminate_all(chan);
> +	sio_synchronize(chan);
> +	vchan_free_chan_resources(&to_sio_chan(chan)->vc);
> +}
> +
> +static struct dma_chan *sio_dma_of_xlate(struct of_phandle_args *dma_spec,
> +					 struct of_dma *ofdma)
> +{
> +	struct sio_data *sio = (struct sio_data *) ofdma->of_dma_data;
> +	unsigned int index = dma_spec->args[0];
> +
> +	if (dma_spec->args_count != 1 || index >= sio->nchannels)
> +		return ERR_PTR(-EINVAL);
> +
> +	return dma_get_slave_channel(&sio->channels[index].vc.chan);
> +}
> +
> +static void sio_rtk_crashed(void *cookie)
> +{
> +	struct sio_data *sio = cookie;
> +
> +	dev_err(sio->dev, "SIO down (crashed)");
> +}
> +
> +static void sio_process_report(struct sio_chan *siochan)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&siochan->vc.lock, flags);
> +	if (siochan->current_tx) {
> +		struct sio_tx *tx = siochan->current_tx;
> +
> +		if (tx->ninflight)
> +			tx->ninflight--;
> +		vchan_cyclic_callback(&tx->vd);
> +		if (!sio_fill_in_locked(siochan) && !tx->ninflight)
> +			complete(&tx->done);
> +	}
> +	spin_unlock_irqrestore(&siochan->vc.lock, flags);
> +}
> +
> +static void sio_recv_msg(void *cookie, u8 ep, u64 msg)
> +{
> +	struct sio_data *sio = cookie;
> +	struct sio_tagdata *tags = &sio->tags;
> +	u32 data;
> +	u8 param, type, tag, sioep;
> +
> +	if (ep != EP_SIO)
> +		goto unknown;
> +
> +	data  = FIELD_GET(SIOMSG_DATA, msg);
> +	param = FIELD_GET(SIOMSG_PARAM, msg);
> +	type  = FIELD_GET(SIOMSG_TYPE, msg);
> +	tag   = FIELD_GET(SIOMSG_TAG, msg);
> +	sioep = FIELD_GET(SIOMSG_EP, msg);
> +
> +	switch (type) {
> +	case MSG_STARTED:
> +		dev_info(sio->dev, "SIO protocol v%u\n", data);
> +		type = MSG_ACK; /* Pretend this is an ACK */
> +		fallthrough;
> +	case MSG_ACK:
> +	case MSG_NACK:
> +		if (WARN_ON(tag >= SIO_NTAGS))
> +			break;
> +
> +		if (tags->atomic[tag]) {
> +			sio_ack_callback callback = tags->ack_callback[tag];
> +
> +			if (callback && !WARN_ON(sioep >= sio->nchannels))
> +				callback(&sio->channels[sioep],
> +					 tags->cookie[tag], type == MSG_ACK);
> +			if (type == MSG_NACK)
> +				dev_err(sio->dev, "got a NACK on channel %d\n", sioep);
> +			sio_free_tag(sio, tag);
> +		} else {
> +			tags->acked[tag] = (type == MSG_ACK);
> +			complete(&tags->completions[tag]);
> +		}
> +		break;
> +
> +	case MSG_REPORT:
> +		if (WARN_ON(sioep >= sio->nchannels))
> +			break;
> +
> +		sio_process_report(&sio->channels[sioep]);
> +		break;
> +
> +	default:
> +		goto unknown;
> +	}
> +	return;
> +
> +unknown:
> +	dev_warn(sio->dev, "received unknown message: ep %x data %016llx\n",
> +		 ep, msg);
> +}
> +
> +static int _sio_send_siomsg(struct sio_data *sio, u64 msg, bool atomic,
> +			    sio_ack_callback ack_callback, void *cookie)
> +{
> +	int tag, ret;
> +
> +	tag = sio_alloc_tag(sio);
> +	if (tag < 0)
> +		return tag;
> +
> +	if (atomic)
> +		sio_set_tag_atomic(sio, tag, ack_callback, cookie);
> +	else
> +		reinit_completion(&sio->tags.completions[tag]);
> +
> +	msg &= ~SIOMSG_TAG;
> +	msg |= FIELD_PREP(SIOMSG_TAG, tag);
> +	ret = apple_rtkit_send_message(sio->rtk, EP_SIO, msg, NULL,
> +				       atomic);
> +	if (ret < 0) {
> +		sio_free_tag(sio, tag);
> +		return ret;
> +	}
> +
> +	return tag;
> +}
> +
> +static int sio_send_siomsg(struct sio_data *sio, u64 msg)
> +{
> +	return _sio_send_siomsg(sio, msg, false, NULL, NULL);
> +}
> +
> +static int sio_send_siomsg_atomic(struct sio_data *sio, u64 msg,
> +				  sio_ack_callback ack_callback,
> +				  void *cookie)
> +{
> +	return _sio_send_siomsg(sio, msg, true, ack_callback, cookie);
> +}
> +
> +static int sio_call(struct sio_data *sio, u64 msg)
> +{
> +	int tag, ret;
> +
> +	tag = sio_send_siomsg(sio, msg);
> +	if (tag < 0)
> +		return tag;
> +
> +	ret = wait_for_completion_timeout(&sio->tags.completions[tag],
> +					  msecs_to_jiffies(SIO_CALL_TIMEOUT_MS));
> +	if (!ret) {
> +		dev_warn(sio->dev, "call %8x timed out\n", msg);
> +		sio_free_tag(sio, tag);
> +		return -ETIME;
> +	}
> +
> +	ret = sio->tags.acked[tag];
> +	sio_free_tag(sio, tag);
> +
> +	return ret;
> +}
> +
> +static const struct apple_rtkit_ops sio_rtkit_ops = {
> +	.crashed = sio_rtk_crashed,
> +	.recv_message = sio_recv_msg,
> +};

so we ahve a remote processor which we send message to right? 

> +static int sio_device_config(struct dma_chan *chan,
> +			     struct dma_slave_config *config)
> +{
> +	struct sio_chan *siochan = to_sio_chan(chan);
> +	struct sio_data *sio = siochan->host;
> +	bool is_tx = sio_chan_direction(siochan->no) == DMA_MEM_TO_DEV;
> +	struct sio_shmem_chan_config *cfg = sio->shmem;
> +	int ret;
> +
> +	switch (is_tx ? config->dst_addr_width : config->src_addr_width) {
> +	case DMA_SLAVE_BUSWIDTH_1_BYTE:
> +		cfg->datashape = 0;
> +		break;
> +	case DMA_SLAVE_BUSWIDTH_2_BYTES:
> +		cfg->datashape = 1;
> +		break;
> +	case DMA_SLAVE_BUSWIDTH_4_BYTES:
> +		cfg->datashape = 2;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	cfg->fifo = 0x800;
> +	cfg->limit = 0x800;
> +	cfg->threshold = 0x800;
> +	dma_wmb();

??

> +
> +	ret = sio_call(sio, FIELD_PREP(SIOMSG_TYPE, MSG_CONFIGURE) |
> +			    FIELD_PREP(SIOMSG_EP, siochan->no));

this does not sound okay, can you explain why this call is here

> +
> +	if (ret == 1)
> +		ret = 0;
> +	else if (ret == 0)
> +		ret = -EINVAL;
> +	return ret;
> +}
> +
> +static int sio_alloc_shmem(struct sio_data *sio)
> +{
> +	dma_addr_t iova;
> +	int err;
> +
> +	sio->shmem = dma_alloc_coherent(sio->dev, SIO_SHMEM_SIZE,
> +					&iova, GFP_KERNEL);
> +	if (!sio->shmem)
> +		return -ENOMEM;
> +
> +	sio->shmem_desc_base = (struct sio_coproc_desc *) (sio->shmem + 56);
> +	sio->desc_allocated = devm_kzalloc(sio->dev, SIO_NO_DESC_SLOTS / 32,
> +					   GFP_KERNEL);
> +	if (!sio->desc_allocated)
> +		return -ENOMEM;
> +
> +	err = sio_call(sio, FIELD_PREP(SIOMSG_TYPE, MSG_SETUP) |
> +			    FIELD_PREP(SIOMSG_PARAM, 1) |
> +			    FIELD_PREP(SIOMSG_DATA, iova >> 12));
> +	if (err != 1) {
> +		if (err == 0)
> +			err = -EINVAL;
> +		return err;
> +	}
> +
> +	err = sio_call(sio, FIELD_PREP(SIOMSG_TYPE, MSG_SETUP) |
> +			    FIELD_PREP(SIOMSG_PARAM, 2) |
> +			    FIELD_PREP(SIOMSG_DATA, SIO_SHMEM_SIZE));
> +	if (err != 1) {
> +		if (err == 0)
> +			err = -EINVAL;
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int sio_send_dt_params(struct sio_data *sio)
> +{
> +	struct device_node *np = sio->dev->of_node;
> +	const char *propname = "apple,sio-firmware-params";
> +	int nparams, err, i;
> +
> +	nparams = of_property_count_u32_elems(np, propname);
> +	if (nparams < 0) {
> +		err = nparams;
> +		goto badprop;
> +	}
> +
> +	for (i = 0; i < nparams / 2; i++) {
> +		u32 key, val;
> +
> +		err = of_property_read_u32_index(np, propname, 2 * i, &key);
> +		if (err)
> +			goto badprop;
> +		err = of_property_read_u32_index(np, propname, 2 * i + 1, &val);
> +		if (err)
> +			goto badprop;
> +
> +		err = sio_call(sio, FIELD_PREP(SIOMSG_TYPE, MSG_SETUP) |
> +				    FIELD_PREP(SIOMSG_PARAM, key & 0xff) |
> +				    FIELD_PREP(SIOMSG_EP, key >> 8) |
> +				    FIELD_PREP(SIOMSG_DATA, val));
> +		if (err < 1) {
> +			if (err == 0)
> +				err = -ENXIO;
> +			return dev_err_probe(sio->dev, err, "sending SIO parameter %#x value %#x\n",
> +					     key, val);
> +		}
> +	}
> +
> +	return 0;
> +
> +badprop:
> +	return dev_err_probe(sio->dev, err, "failed to read '%s'\n", propname);
> +}
> +
> +static int sio_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct sio_data *sio;
> +	struct dma_device *dma;
> +	int nchannels;
> +	int err, i;
> +
> +	err = of_property_read_u32(np, "dma-channels", &nchannels);
> +	if (err || nchannels > NCHANNELS_MAX)
> +		return dev_err_probe(&pdev->dev, -EINVAL,
> +				     "missing or invalid dma-channels property\n");
> +
> +	sio = devm_kzalloc(&pdev->dev, struct_size(sio, channels, nchannels), GFP_KERNEL);
> +	if (!sio)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, sio);
> +	sio->dev = &pdev->dev;
> +	sio->nchannels = nchannels;
> +
> +	sio->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(sio->base))
> +		return PTR_ERR(sio->base);
> +
> +	sio->rtk = devm_apple_rtkit_init(&pdev->dev, sio, NULL, 0, &sio_rtkit_ops);
> +	if (IS_ERR(sio->rtk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(sio->rtk),
> +				     "couldn't initialize rtkit\n");
> +	for (i = 1; i < SIO_NTAGS; i++)
> +		init_completion(&sio->tags.completions[i]);
> +
> +	dma = &sio->dma;
> +	dma_cap_set(DMA_PRIVATE, dma->cap_mask);
> +	dma_cap_set(DMA_CYCLIC, dma->cap_mask);
> +
> +	dma->dev = &pdev->dev;
> +	dma->device_free_chan_resources = sio_free_chan_resources;
> +	dma->device_tx_status = sio_tx_status;
> +	dma->device_issue_pending = sio_issue_pending;
> +	dma->device_terminate_all = sio_terminate_all;
> +	dma->device_synchronize = sio_synchronize;
> +	dma->device_prep_dma_cyclic = sio_prep_dma_cyclic;
> +	dma->device_config = sio_device_config;
> +
> +	dma->directions = BIT(DMA_MEM_TO_DEV);
> +	dma->residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> +	dma->dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
> +			       BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
> +			       BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
> +
> +	INIT_LIST_HEAD(&dma->channels);
> +	for (i = 0; i < nchannels; i++) {
> +		struct sio_chan *siochan = &sio->channels[i];
> +
> +		siochan->host = sio;
> +		siochan->no = i;
> +		siochan->vc.desc_free = sio_tx_free;
> +		INIT_WORK(&siochan->terminate_wq, sio_terminate_work);
> +		vchan_init(&siochan->vc, dma);
> +	}
> +
> +	writel(CPU_CONTROL_RUN, sio->base + REG_CPU_CONTROL);
> +
> +	err = apple_rtkit_boot(sio->rtk);
> +	if (err)
> +		return dev_err_probe(&pdev->dev, err, "SIO did not boot\n");
> +
> +	err = apple_rtkit_start_ep(sio->rtk, EP_SIO);
> +	if (err)
> +		return dev_err_probe(&pdev->dev, err, "starting SIO endpoint\n");
> +
> +	err = sio_call(sio, FIELD_PREP(SIOMSG_TYPE, MSG_START));
> +	if (err < 1) {
> +		if (err == 0)
> +			err = -ENXIO;
> +		return dev_err_probe(&pdev->dev, err, "starting SIO service\n");
> +	}
> +
> +	err = sio_send_dt_params(sio);
> +	if (err < 0)
> +		return dev_err_probe(&pdev->dev, err, "failed to send boot-up parameters\n");
> +
> +	err = sio_alloc_shmem(sio);
> +	if (err < 0)
> +		return err;
> +
> +	err = dma_async_device_register(&sio->dma);
> +	if (err)
> +		return dev_err_probe(&pdev->dev, err, "failed to register DMA device\n");
> +
> +	err = of_dma_controller_register(pdev->dev.of_node, sio_dma_of_xlate, sio);
> +	if (err) {
> +		dma_async_device_unregister(&sio->dma);
> +		return dev_err_probe(&pdev->dev, err, "failed to register with OF\n");
> +	}
> +
> +	return 0;
> +}
> +
> +static int sio_remove(struct platform_device *pdev)
> +{
> +	struct sio_data *sio = platform_get_drvdata(pdev);
> +
> +	of_dma_controller_free(pdev->dev.of_node);
> +	dma_async_device_unregister(&sio->dma);
> +	return 0;
> +}
> +
> +static const struct of_device_id sio_of_match[] = {
> +	{ .compatible = "apple,sio", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, sio_of_match);
> +
> +static struct platform_driver apple_sio_driver = {
> +	.driver = {
> +		.name = "apple-sio",
> +		.of_match_table = sio_of_match,
> +	},
> +	.probe = sio_probe,
> +	.remove = sio_remove,
> +};
> +module_platform_driver(apple_sio_driver);
> +
> +MODULE_AUTHOR("Martin Povišer <povik+lin@cutebit.org>");
> +MODULE_DESCRIPTION("Driver for SIO coprocessor on Apple SoCs");
> +MODULE_LICENSE("Dual MIT/GPL");
> -- 
> 2.38.3

-- 
~Vinod