RE: [PATCH V3 3/4] mailbox: imx: add SCU MU support

[Peng Fan]

Hi Oleksij,

> Subject: Re: [PATCH V3 3/4] mailbox: imx: add SCU MU support
> 
> Hi,
> 
> On 26.02.20 05:40, peng.fan@xxxxxxx wrote:
> > From: Peng Fan <peng.fan@xxxxxxx>
> >
> > i.MX8/8X SCU MU is dedicated for communication between SCU and
> > Cortex-A cores from hardware design, and could not be reused for other
> purpose.
> >
> > Per i.MX8/8X Reference mannual, Chapter "12.9.2.3.2 Messaging
> Examples",
> >   Passing short messages: Transmit register(s) can be used to pass
> >   short messages from one to four words in length. For example, when
> >   a four-word message is desired, only one of the registers needs to
> >   have its corresponding interrupt enable bit set at the receiver side;
> >   the messageâs first three words are written to the registers whose
> >   interrupt is masked, and the fourth word is written to the other
> >   register (which triggers an interrupt at the receiver side).
> >
> > i.MX8/8X SCU firmware IPC is an implementation of passing short
> > messages. But current imx-mailbox driver only support one word
> > message, i.MX8/8X linux side firmware has to request four TX and four
> > RX to support IPC to SCU firmware. This is low efficent and more
> > interrupts triggered compared with one TX and one RX.
> >
> > To make SCU MU work,
> >    - parse the size of msg.
> >    - Only enable TR0/RR0 interrupt for transmit/receive message.
> >    - For TX/RX, only support one TX channel and one RX channel
> >
> > Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> > ---
> >
> > V3:
> >   Added scu type tx/rx and SCU MU type
> >
> >   drivers/mailbox/imx-mailbox.c | 65
> ++++++++++++++++++++++++++++++++++++++++++-
> >   1 file changed, 64 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mailbox/imx-mailbox.c
> > b/drivers/mailbox/imx-mailbox.c index 901a3431fdb5..41664a64c5fd
> > 100644
> > --- a/drivers/mailbox/imx-mailbox.c
> > +++ b/drivers/mailbox/imx-mailbox.c
> > @@ -4,6 +4,7 @@
> >    */
> >
> >   #include <linux/clk.h>
> > +#include <linux/firmware/imx/ipc.h>
> >   #include <linux/interrupt.h>
> >   #include <linux/io.h>
> >   #include <linux/kernel.h>
> > @@ -38,11 +39,17 @@ enum imx_mu_chan_type {
> >
> >   enum imx_mu_type {
> >   	IMX_MU_TYPE_GENERIC,
> > +	IMX_MU_TYPE_SCU,
> >   };
> >
> >   struct imx_mu_priv;
> >   struct imx_mu_con_priv;
> >
> > +struct imx_sc_rpc_msg_max {
> > +	struct imx_sc_rpc_msg hdr;
> > +	u32 data[7];
> > +} __packed __aligned(4);;
> > +
> >   struct imx_mu_dcfg {
> >   	enum imx_mu_type type;
> >   	int (*tx)(struct imx_mu_priv *priv, struct imx_mu_con_priv *cp,
> > void *data); @@ -141,6 +148,48 @@ static int imx_mu_generic_rx(struct
> imx_mu_priv *priv,
> >   	return 0;
> >   }
> >
> > +static int imx_mu_scu_tx(struct imx_mu_priv *priv,
> > +			 struct imx_mu_con_priv *cp,
> > +			 void *data)
> > +{
> > +	struct imx_sc_rpc_msg_max *msg = data;
> > +	u32 *arg = data;
> > +	int i;
> > +
> > +	switch (cp->type) {
> > +	case IMX_MU_TYPE_TX:
> 
> please add sanity check if msg->hdr.size can be handled by this driver version.

Yes, I forgot to add that. Should as below:

if (msg->hdr.size > sizeof(struct imx_sc_rpc_msg_max))
	return -EINVAL;

> 
> > +		for (i = 0; i < msg->hdr.size; i++) {
> > +			imx_mu_write(priv, *arg++,
> > +				     priv->dcfg->xTR[i % 4]);
> > +		}
> > +		imx_mu_xcr_rmw(priv, IMX_MU_xCR_TIEn(cp->idx), 0);
> > +		break;
> > +	default:
> > +		dev_warn_ratelimited(priv->dev, "Send data on wrong channel
> type: %d\n", cp->type);
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int imx_mu_scu_rx(struct imx_mu_priv *priv,
> > +			 struct imx_mu_con_priv *cp)
> > +{
> > +	struct imx_sc_rpc_msg_max msg;
> > +	u32 *data = (u32 *)&msg;
> > +	int i;
> > +
> > +	imx_mu_xcr_rmw(priv, 0, IMX_MU_xCR_RIEn(0));
> > +	*data++ = imx_mu_read(priv, priv->dcfg->xRR[0]);
> 
> please add sanity check. the message size should not be higher then
> sizeof(msg)

Yes.

> 
> > +	for (i = 1; i < msg.hdr.size; i++)
> > +		*data++ = imx_mu_read(priv, priv->dcfg->xRR[i % 4]);
> > +
> > +	imx_mu_xcr_rmw(priv, IMX_MU_xCR_RIEn(0), 0);
> 
> Please do not forget to handle properly new msg size in your rx_callback. In
> previous implementation the message size was 4byte.

My patch could handle size larger than 4 words. The previous implementation
to limit 4 words is not good.

> 
> > +	mbox_chan_received_data(cp->chan, (void *)&msg);
> > +
> > +	return 0;
> > +}
> > +
> >   static void imx_mu_txdb_tasklet(unsigned long data)
> >   {
> >   	struct imx_mu_con_priv *cp = (struct imx_mu_con_priv *)data; @@
> > -274,6 +323,7 @@ static struct mbox_chan * imx_mu_xlate(struct
> mbox_controller *mbox,
> >   				       const struct of_phandle_args *sp)
> >   {
> >   	u32 type, idx, chan;
> > +	struct imx_mu_priv *priv = to_imx_mu_priv(mbox);
> >
> >   	if (sp->args_count != 2) {
> >   		dev_err(mbox->dev, "Invalid argument count %d\n",
> sp->args_count);
> > @@ -284,7 +334,9 @@ static struct mbox_chan * imx_mu_xlate(struct
> mbox_controller *mbox,
> >   	idx = sp->args[1]; /* index */
> >   	chan = type * 4 + idx;
> >
> > -	if (chan >= mbox->num_chans) {
> > +	if (chan >= mbox->num_chans ||
> > +	    (priv->dcfg->type == IMX_MU_TYPE_SCU &&
> > +	     type < IMX_MU_TYPE_TXDB && idx > 0)) {
> 
> We need this check since mbox->num_chans do not reflects new reality. Now
> we have only 2 channels. One RX and one TX. No idea if we need doorbell
> channels for SCU. If doorbells are not supported, it is better to add a separate
> imx_mu_xlate for SCU

TXDB currently not supported, but I am not sure whether it will be supported
in future. I could add a separate xlate as you suggested, since TXDB not support
now.

> 
> and add SCU specific channel init in probe in addition to:
>          for (i = 0; i < IMX_MU_CHANS; i++) {
> 
>                  struct imx_mu_con_priv *cp = &priv->con_priv[i];
> 
> 
> 
>                  cp->idx = i % 4;
> 
>                  cp->type = i >> 2;
> 
>                  cp->chan = &priv->mbox_chans[i];
> 
>                  priv->mbox_chans[i].con_priv = cp;
> 
>                  snprintf(cp->irq_desc, sizeof(cp->irq_desc),
> 
>                           "imx_mu_chan[%i-%i]", cp->type, cp->idx);
> 
>          }
> 
> There is no need to init unsupported channels. Please pack it in separate
> function

ok. I just want to reuse current code as more as possible and avoid
adding too much new code.

Thanks,
Peng.

> 
> >   		dev_err(mbox->dev, "Not supported channel number: %d.
> (type: %d, idx: %d)\n", chan, type, idx);
> >   		return ERR_PTR(-EINVAL);
> >   	}
> > @@ -401,9 +453,20 @@ static const struct imx_mu_dcfg
> imx_mu_cfg_imx7ulp = {
> >   	.xCR	= 0x64,
> >   };
> >
> > +static const struct imx_mu_dcfg imx_mu_cfg_imx8_scu = {
> > +	.type	= IMX_MU_TYPE_SCU,
> > +	.tx	= imx_mu_scu_tx,
> > +	.rx	= imx_mu_scu_rx,
> > +	.xTR	= {0x0, 0x4, 0x8, 0xc},
> > +	.xRR	= {0x10, 0x14, 0x18, 0x1c},
> > +	.xSR	= 0x20,
> > +	.xCR	= 0x24,
> > +};
> > +
> >   static const struct of_device_id imx_mu_dt_ids[] = {
> >   	{ .compatible = "fsl,imx7ulp-mu", .data = &imx_mu_cfg_imx7ulp },
> >   	{ .compatible = "fsl,imx6sx-mu", .data = &imx_mu_cfg_imx6sx },
> > +	{ .compatible = "fsl,imx8-mu-scu", .data = &imx_mu_cfg_imx8_scu },
> >   	{ },
> >   };
> >   MODULE_DEVICE_TABLE(of, imx_mu_dt_ids);
> >
> 
> Kind regards,
> Oleksij Rempel
> 
> --
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