Re: [PATCH 2/2] firmware: arm_scmi: Support 'reg-io-width' property for shared memory

[Cristian Marussi <cristian.marussi@arm.com>]

On Sat, Aug 10, 2024 at 02:46:21PM -0700, Florian Fainelli wrote:
> Some shared memory areas might only support a certain access width,
> (e.g.: 32 bits accesses only). Update the shmem layer to support
> reading from and writing to such shared memory area using the specified
> I/O width in the Device Tree. The various transport layers making use of
> the shmem.c code are updated accordingly to pass the I/O width to the
> routines that need it.

Hi Florian,

I only glanced quicky through the series...a few remarks below.

> 
> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
> ---
>  drivers/firmware/arm_scmi/common.h            | 14 +++-
>  .../arm_scmi/scmi_transport_mailbox.c         | 12 ++-
>  .../firmware/arm_scmi/scmi_transport_optee.c  |  7 +-
>  .../firmware/arm_scmi/scmi_transport_smc.c    | 10 ++-
>  drivers/firmware/arm_scmi/shmem.c             | 77 ++++++++++++++++---
>  5 files changed, 96 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> index 69928bbd01c2..97dae844a190 100644
> --- a/drivers/firmware/arm_scmi/common.h
> +++ b/drivers/firmware/arm_scmi/common.h
> @@ -170,6 +170,7 @@ void scmi_protocol_release(const struct scmi_handle *handle, u8 protocol_id);
>   *		       This can be dynamically set by transports at run-time
>   *		       inside their provided .chan_setup().
>   * @transport_info: Transport layer related information
> + * @shmem_io_width: I/O width in bytes of the shared memory area
>   */
>  struct scmi_chan_info {
>  	int id;
> @@ -178,6 +179,7 @@ struct scmi_chan_info {
>  	struct scmi_handle *handle;
>  	bool no_completion_irq;
>  	void *transport_info;
> +	u32 shmem_io_width;
>  };

As you said you dont need this if you embed it inside the
transpor_info...but...
>  
>  /**
> @@ -336,13 +338,16 @@ struct scmi_shared_mem;
>  struct scmi_shared_mem_operations {
>  	void (*tx_prepare)(struct scmi_shared_mem __iomem *shmem,
>  			   struct scmi_xfer *xfer,
> -			   struct scmi_chan_info *cinfo);
> +			   struct scmi_chan_info *cinfo,
> +			   u32 shmem_io_width);

...maybe also you dont need this additional parameters if you setup
upfront the shmem ops to operate ONLY on the configured size...

...I mean all of this seems to be a one-shot setup procedure so it
would be sensible to just configuire the shmem ops pointers once-for all
to ONLY use the proper size helper method...since mixed-size usage at
runtime seems NOT be an option given how the binding is used...

...but I can see that in this case you will need to change a bit
how the scmi_shared_mem_operations are setup...since now they are a
const global and initialized fully at driver init in 

	scmi_trans_core_ops.shmem = scmi_shared_mem_operations_get(); 

..so, in case you want to setup only once the properly sized helpers at
run-time, all of this should happen instead at probe-time and you should
have a per-probe-instance scmni_trans_core_ops struct since you could have
multiple SCMI nodes using multiple shmem transports with different size...
(in theory...)

>  	u32 (*read_header)(struct scmi_shared_mem __iomem *shmem);
>  
>  	void (*fetch_response)(struct scmi_shared_mem __iomem *shmem,
> -			       struct scmi_xfer *xfer);
> +			       struct scmi_xfer *xfer,
> +			       u32 shmem_io_width);
>  	void (*fetch_notification)(struct scmi_shared_mem __iomem *shmem,
> -				   size_t max_len, struct scmi_xfer *xfer);
> +				   size_t max_len, struct scmi_xfer *xfer,
> +				   u32 shmem_io_width);
>  	void (*clear_channel)(struct scmi_shared_mem __iomem *shmem);
>  	bool (*poll_done)(struct scmi_shared_mem __iomem *shmem,
>  			  struct scmi_xfer *xfer);
> @@ -350,7 +355,8 @@ struct scmi_shared_mem_operations {
>  	bool (*channel_intr_enabled)(struct scmi_shared_mem __iomem *shmem);
>  	void __iomem *(*setup_iomap)(struct scmi_chan_info *cinfo,
>  				     struct device *dev,
> -				     bool tx, struct resource *res);
> +				     bool tx, struct resource *res,
> +				     u32 *shmem_io_width);
>  };
>  
>  const struct scmi_shared_mem_operations *scmi_shared_mem_operations_get(void);
> diff --git a/drivers/firmware/arm_scmi/scmi_transport_mailbox.c b/drivers/firmware/arm_scmi/scmi_transport_mailbox.c
> index dc5ca894d5eb..6bd876875655 100644
> --- a/drivers/firmware/arm_scmi/scmi_transport_mailbox.c
> +++ b/drivers/firmware/arm_scmi/scmi_transport_mailbox.c
> @@ -33,6 +33,7 @@ struct scmi_mailbox {
>  	struct mbox_chan *chan_platform_receiver;
>  	struct scmi_chan_info *cinfo;
>  	struct scmi_shared_mem __iomem *shmem;
> +	u32 shmem_io_width;
>  };
>  
>  #define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
> @@ -43,7 +44,8 @@ static void tx_prepare(struct mbox_client *cl, void *m)
>  {
>  	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
>  
> -	core->shmem->tx_prepare(smbox->shmem, m, smbox->cinfo);
> +	core->shmem->tx_prepare(smbox->shmem, m, smbox->cinfo,
> +				smbox->shmem_io_width);
>  }
>  
>  static void rx_callback(struct mbox_client *cl, void *m)
> @@ -197,7 +199,8 @@ static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
>  	if (!smbox)
>  		return -ENOMEM;
>  
> -	smbox->shmem = core->shmem->setup_iomap(cinfo, dev, tx, NULL);
> +	smbox->shmem = core->shmem->setup_iomap(cinfo, dev, tx, NULL,
> +						&smbox->shmem_io_width);
>  	if (IS_ERR(smbox->shmem))
>  		return PTR_ERR(smbox->shmem);
>  
> @@ -298,7 +301,7 @@ static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
>  {
>  	struct scmi_mailbox *smbox = cinfo->transport_info;
>  
> -	core->shmem->fetch_response(smbox->shmem, xfer);
> +	core->shmem->fetch_response(smbox->shmem, xfer, smbox->shmem_io_width);
>  }
>  
>  static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
> @@ -306,7 +309,8 @@ static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
>  {
>  	struct scmi_mailbox *smbox = cinfo->transport_info;
>  
> -	core->shmem->fetch_notification(smbox->shmem, max_len, xfer);
> +	core->shmem->fetch_notification(smbox->shmem, max_len, xfer,
> +					smbox->shmem_io_width);
>  }
>  
>  static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
> diff --git a/drivers/firmware/arm_scmi/scmi_transport_optee.c b/drivers/firmware/arm_scmi/scmi_transport_optee.c
> index 08911f40d1ff..9f6804647b29 100644
> --- a/drivers/firmware/arm_scmi/scmi_transport_optee.c
> +++ b/drivers/firmware/arm_scmi/scmi_transport_optee.c
> @@ -350,7 +350,8 @@ static int setup_dynamic_shmem(struct device *dev, struct scmi_optee_channel *ch
>  static int setup_static_shmem(struct device *dev, struct scmi_chan_info *cinfo,
>  			      struct scmi_optee_channel *channel)
>  {
> -	channel->req.shmem = core->shmem->setup_iomap(cinfo, dev, true, NULL);
> +	channel->req.shmem = core->shmem->setup_iomap(cinfo, dev, true, NULL,
> +						      NULL);
>  	if (IS_ERR(channel->req.shmem))
>  		return PTR_ERR(channel->req.shmem);
>  
> @@ -465,7 +466,7 @@ static int scmi_optee_send_message(struct scmi_chan_info *cinfo,
>  		ret = invoke_process_msg_channel(channel,
>  						 core->msg->command_size(xfer));
>  	} else {
> -		core->shmem->tx_prepare(channel->req.shmem, xfer, cinfo);
> +		core->shmem->tx_prepare(channel->req.shmem, xfer, cinfo, 0);
>  		ret = invoke_process_smt_channel(channel);
>  	}
>  
> @@ -484,7 +485,7 @@ static void scmi_optee_fetch_response(struct scmi_chan_info *cinfo,
>  		core->msg->fetch_response(channel->req.msg,
>  					  channel->rx_len, xfer);
>  	else
> -		core->shmem->fetch_response(channel->req.shmem, xfer);
> +		core->shmem->fetch_response(channel->req.shmem, xfer, 0);
>  }
>  
>  static void scmi_optee_mark_txdone(struct scmi_chan_info *cinfo, int ret,
> diff --git a/drivers/firmware/arm_scmi/scmi_transport_smc.c b/drivers/firmware/arm_scmi/scmi_transport_smc.c
> index c6c69a17a9cc..4e7b2ac1c7e8 100644
> --- a/drivers/firmware/arm_scmi/scmi_transport_smc.c
> +++ b/drivers/firmware/arm_scmi/scmi_transport_smc.c
> @@ -60,6 +60,7 @@ struct scmi_smc {
>  	int irq;
>  	struct scmi_chan_info *cinfo;
>  	struct scmi_shared_mem __iomem *shmem;
> +	u32 shmem_io_width;
>  	/* Protect access to shmem area */
>  	struct mutex shmem_lock;
>  #define INFLIGHT_NONE	MSG_TOKEN_MAX
> @@ -144,7 +145,8 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
>  	if (!scmi_info)
>  		return -ENOMEM;
>  
> -	scmi_info->shmem = core->shmem->setup_iomap(cinfo, dev, tx, &res);
> +	scmi_info->shmem = core->shmem->setup_iomap(cinfo, dev, tx, &res,
> +						    &scmi_info->shmem_io_width);
>  	if (IS_ERR(scmi_info->shmem))
>  		return PTR_ERR(scmi_info->shmem);
>  
> @@ -229,7 +231,8 @@ static int smc_send_message(struct scmi_chan_info *cinfo,
>  	 */
>  	smc_channel_lock_acquire(scmi_info, xfer);
>  
> -	core->shmem->tx_prepare(scmi_info->shmem, xfer, cinfo);
> +	core->shmem->tx_prepare(scmi_info->shmem, xfer, cinfo,
> +				scmi_info->shmem_io_width);
>  
>  	if (scmi_info->cap_id != ULONG_MAX)
>  		arm_smccc_1_1_invoke(scmi_info->func_id, scmi_info->cap_id, 0,
> @@ -253,7 +256,8 @@ static void smc_fetch_response(struct scmi_chan_info *cinfo,
>  {
>  	struct scmi_smc *scmi_info = cinfo->transport_info;
>  
> -	core->shmem->fetch_response(scmi_info->shmem, xfer);
> +	core->shmem->fetch_response(scmi_info->shmem, xfer,
> +				    scmi_info->shmem_io_width);
>  }
>  
>  static void smc_mark_txdone(struct scmi_chan_info *cinfo, int ret,
> diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c
> index 01d8a9398fe8..192262d63baa 100644
> --- a/drivers/firmware/arm_scmi/shmem.c
> +++ b/drivers/firmware/arm_scmi/shmem.c
> @@ -34,9 +34,20 @@ struct scmi_shared_mem {
>  	u8 msg_payload[];
>  };
>  
> +#define __shmem_copy_toio_tpl(s)			\
> +	for (unsigned int i = 0; i < xfer->tx.len; i += shmem_io_width)		\
> +		iowrite##s(((u##s *)(xfer->tx.buf))[i / shmem_io_width],	\
> +			   shmem->msg_payload + i);
> +
> +#define __shmem_copy_fromio_tpl(s)			\
> +	for (unsigned int i = 0; i < xfer->rx.len; i += shmem_io_width)		\
> +		((u##s *)(xfer->rx.buf))[i / shmem_io_width] = 			\
> +			 ioread##s(shmem->msg_payload + shmem_io_width + i);
> +
>  static void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem,
>  			     struct scmi_xfer *xfer,
> -			     struct scmi_chan_info *cinfo)
> +			     struct scmi_chan_info *cinfo,
> +			     u32 shmem_io_width)
>  {
>  	ktime_t stop;
>  
> @@ -72,8 +83,25 @@ static void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem,
>  		  &shmem->flags);
>  	iowrite32(sizeof(shmem->msg_header) + xfer->tx.len, &shmem->length);
>  	iowrite32(pack_scmi_header(&xfer->hdr), &shmem->msg_header);

what about these (and other) header reads if reg-io-width is defined as < 32 ?
Should not these accesses be size-wise too ? or I am missing smth ...
(...and if yes I would once more say that all of this should be setup once for
all at setup time and not checked against a parameter at run time for each access...)

> -	if (xfer->tx.buf)
> -		memcpy_toio(shmem->msg_payload, xfer->tx.buf, xfer->tx.len);
> +	if (xfer->tx.buf) {
> +		switch (shmem_io_width) {
> +		case 1:
> +			__shmem_copy_toio_tpl(8);
> +			break;
> +		case 2:
> +			__shmem_copy_toio_tpl(16);
> +			break;
> +		case 4:
> +			__shmem_copy_toio_tpl(32);
> +			break;
> +		case 8:
> +			__shmem_copy_toio_tpl(64);
> +			break;
> +		default:
> +			memcpy_toio(shmem->msg_payload, xfer->tx.buf, xfer->tx.len);
> +			break;

...as said above, this switch could be avoided by setting up the
transport access size once for all at setup time with properly
sized-helpers...


> +		}
> +	}
>  }
>  
>  static u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem)
> @@ -81,8 +109,34 @@ static u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem)
>  	return ioread32(&shmem->msg_header);
>  }
>  
> +static void __shmem_fetch_resp_notif_data(struct scmi_xfer *xfer,
> +					  struct scmi_shared_mem __iomem *shmem,
> +					  u32 shmem_io_width)
> +{
> +	/* Take a copy to the rx buffer.. */
> +	switch (shmem_io_width) {
> +	case 1:
> +		__shmem_copy_fromio_tpl(8);
> +		break;
> +	case 2:
> +		__shmem_copy_fromio_tpl(16);
> +		break;
> +	case 4:
> +		__shmem_copy_fromio_tpl(32);
> +		break;
> +	case 8:
> +		__shmem_copy_fromio_tpl(32);
> +		break;
> +	default:
> +		memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4,
> +			      xfer->rx.len);
> +		break;
> +	}
> +}
> +
>  static void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
> -				 struct scmi_xfer *xfer)
> +				 struct scmi_xfer *xfer,
> +				 u32 shmem_io_width)
>  {
>  	size_t len = ioread32(&shmem->length);
>  
> @@ -90,20 +144,19 @@ static void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
>  	/* Skip the length of header and status in shmem area i.e 8 bytes */
>  	xfer->rx.len = min_t(size_t, xfer->rx.len, len > 8 ? len - 8 : 0);
>  
> -	/* Take a copy to the rx buffer.. */
> -	memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4, xfer->rx.len);
> +	__shmem_fetch_resp_notif_data(xfer, shmem, shmem_io_width);
>  }
>  
>  static void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
> -				     size_t max_len, struct scmi_xfer *xfer)
> +				     size_t max_len, struct scmi_xfer *xfer,
> +				     u32 shmem_io_width)
>  {
>  	size_t len = ioread32(&shmem->length);
>  
>  	/* Skip only the length of header in shmem area i.e 4 bytes */
>  	xfer->rx.len = min_t(size_t, max_len, len > 4 ? len - 4 : 0);
>  
> -	/* Take a copy to the rx buffer.. */
> -	memcpy_fromio(xfer->rx.buf, shmem->msg_payload, xfer->rx.len);
> +	__shmem_fetch_resp_notif_data(xfer, shmem, shmem_io_width);
>  }
>  
>  static void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem)
> @@ -139,7 +192,8 @@ static bool shmem_channel_intr_enabled(struct scmi_shared_mem __iomem *shmem)
>  
>  static void __iomem *shmem_setup_iomap(struct scmi_chan_info *cinfo,
>  				       struct device *dev, bool tx,
> -				       struct resource *res)
> +				       struct resource *res,
> +				       u32 *shmem_io_width)
>  {
>  	struct device_node *shmem __free(device_node);
>  	const char *desc = tx ? "Tx" : "Rx";
> @@ -173,6 +227,9 @@ static void __iomem *shmem_setup_iomap(struct scmi_chan_info *cinfo,
>  		return IOMEM_ERR_PTR(-EADDRNOTAVAIL);
>  	}
>  
> +	if (shmem_io_width)
> +		of_property_read_u32(shmem, "reg-io-width", shmem_io_width);
> +


...this and all the subsequent setup could be moved inside a modified
shared_mem_operations_get(dev) while moving its callsite from driver_init into
driver_probe (probably) insside @scmi_transport_setup....but it will require
a non-trivial amount of changes in the transport to avoid the global core-> ptr.

Thanks,
Cristian