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From:   Peng Fan <peng.fan@nxp.com>
To:     Leonard Crestez <leonard.crestez@nxp.com>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "o.rempel@pengutronix.de" <o.rempel@pengutronix.de>
CC:     "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
        "jassisinghbrar@gmail.com" <jassisinghbrar@gmail.com>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "festevam@gmail.com" <festevam@gmail.com>,
        dl-linux-imx <linux-imx@nxp.com>,
        Anson Huang <anson.huang@nxp.com>,
        Aisheng Dong <aisheng.dong@nxp.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Franck Lenormand <franck.lenormand@nxp.com>
Subject: RE: [PATCH V6 3/4] mailbox: imx: add SCU MU support
Thread-Topic: [PATCH V6 3/4] mailbox: imx: add SCU MU support
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Date:   Wed, 18 Mar 2020 12:17:07 +0000
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> Subject: Re: [PATCH V6 3/4] mailbox: imx: add SCU MU support
>=20
> On 2020-03-04 7:56 AM, Peng Fan wrote:
> > From: Peng Fan <peng.fan@nxp.com>
> >
> > 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 message's 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
> >    - For RX, support receive msg larger than 4 u32 words.
> >    - Support 6 channels, TX0/RX0/RXDB[0-3], not support TXDB.
> >
> > Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
> > Signed-off-by: Peng Fan <peng.fan@nxp.com>
> > ---
> >
> > V6:
> >   Add R-b tag
> >   Use %zu for printk sizeof
> >
> > V5:
> >   Code style cleanup
> >   Add more debug msg
> >   Drop __packed aligned
> >   idx santity check in scu xlate
> >
> > V4:
> >   Added separate chans init and xlate function for SCU MU
> >   Limit chans to TX0/RX0/RXDB[0-3], max 6 chans.
> >   Santity check to msg size
> >
> > V3:
> >   Added scu type tx/rx and SCU MU type
> >
> >   drivers/mailbox/imx-mailbox.c | 134
> ++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 134 insertions(+)
> >
> > diff --git a/drivers/mailbox/imx-mailbox.c
> > b/drivers/mailbox/imx-mailbox.c index df6c4ecd913c..0895ccd23d17
> > 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>
> > @@ -27,6 +28,8 @@
> >   #define IMX_MU_xCR_GIRn(x)	BIT(16 + (3 - (x)))
> >
> >   #define IMX_MU_CHANS		16
> > +/* TX0/RX0/RXDB[0-3] */
> > +#define IMX_MU_SCU_CHANS	6
> >   #define IMX_MU_CHAN_NAME_SIZE	20
> >
> >   enum imx_mu_chan_type {
> > @@ -36,6 +39,11 @@ enum imx_mu_chan_type {
> >   	IMX_MU_TYPE_RXDB,	/* Rx doorbell */
> >   };
> >
> > +struct imx_sc_rpc_msg_max {
> > +	struct imx_sc_rpc_msg hdr;
> > +	u32 data[7];
> > +};
> > +
> >   struct imx_mu_con_priv {
> >   	unsigned int		idx;
> >   	char			irq_desc[IMX_MU_CHAN_NAME_SIZE];
> > @@ -134,6 +142,63 @@ 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 =3D data;
> > +	u32 *arg =3D data;
> > +	int i;
> > +
> > +	switch (cp->type) {
> > +	case IMX_MU_TYPE_TX:
> > +		if (msg->hdr.size > sizeof(*msg)) {
> > +			/*
> > +			 * The real message size can be different to
> > +			 * struct imx_sc_rpc_msg_max size
> > +			 */
> > +			dev_err(priv->dev, "Exceed max msg size (%zu) on TX,
> got: %i\n", sizeof(*msg), msg->hdr.size);
> > +			return -EINVAL;
> > +		}
> > +
> > +		for (i =3D 0; i < msg->hdr.size; i++) > +			imx_mu_write(priv,
> *arg++, priv->dcfg->xTR[i % 4]);
>=20
> Need to poll for TE, otherwise for long messages we could overwrite TR0
> before SCU reads it.

I planned to add a follow up patch for long word messages.
Since you raised it, I'll add check for TX for send, RX for recv.

>=20
> > +
> > +		imx_mu_xcr_rmw(priv, IMX_MU_xCR_TIEn(cp->idx), 0);
>=20
> Shouldn't TIE be armed ahead of writing? In theory SCU could read first
> register before loop above is over.

This is to avoid TX interrupt be triggered early.

>=20
> > +		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 =3D (u32 *)&msg;
> > +	int i;
> > +
> > +	imx_mu_xcr_rmw(priv, 0, IMX_MU_xCR_RIEn(0));
> > +	*data++ =3D imx_mu_read(priv, priv->dcfg->xRR[0]);
> > +
> > +	if (msg.hdr.size > sizeof(msg)) {
> > +		dev_err(priv->dev, "Exceed max msg size (%zu) on RX, got: %i\n",
> > +			sizeof(msg), msg.hdr.size);
> > +		return -EINVAL;
> > +	}
> > +
> > +	for (i =3D 1; i < msg.hdr.size; i++)
> > +		*data++ =3D imx_mu_read(priv, priv->dcfg->xRR[i % 4]);
>=20
> Shouldn't you poll for !RE? It's possible to receive RX interrupt and sta=
rt
> reading before other side writes the second word.

Will add RE check.


Thanks,
Peng.

>=20
> > +
> > +	imx_mu_xcr_rmw(priv, IMX_MU_xCR_RIEn(0), 0);
> > +	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 =3D (struct imx_mu_con_priv *)data; @@
> > -263,6 +328,42 @@ static const struct mbox_chan_ops imx_mu_ops =3D {
> >   	.shutdown =3D imx_mu_shutdown,
> >   };
> >
> > +static struct mbox_chan *imx_mu_scu_xlate(struct mbox_controller
> *mbox,
> > +					  const struct of_phandle_args *sp) {
> > +	u32 type, idx, chan;
> > +
> > +	if (sp->args_count !=3D 2) {
> > +		dev_err(mbox->dev, "Invalid argument count %d\n",
> sp->args_count);
> > +		return ERR_PTR(-EINVAL);
> > +	}
> > +
> > +	type =3D sp->args[0]; /* channel type */
> > +	idx =3D sp->args[1]; /* index */
> > +
> > +	switch (type) {
> > +	case IMX_MU_TYPE_TX:
> > +	case IMX_MU_TYPE_RX:
> > +		if (idx !=3D 0)
> > +			dev_err(mbox->dev, "Invalid chan idx: %d\n", idx);
> > +		chan =3D type;
> > +		break;
> > +	case IMX_MU_TYPE_RXDB:
> > +		chan =3D 2 + idx;
> > +		break;
> > +	default:
> > +		dev_err(mbox->dev, "Invalid chan type: %d\n", type);
> > +		return NULL;
> > +	}
> > +
> > +	if (chan >=3D mbox->num_chans) {
> > +		dev_err(mbox->dev, "Not supported channel number: %d. (type: %d,
> idx: %d)\n", chan, type, idx);
> > +		return ERR_PTR(-EINVAL);
> > +	}
> > +
> > +	return &mbox->chans[chan];
> > +}
> > +
> >   static struct mbox_chan * imx_mu_xlate(struct mbox_controller *mbox,
> >   				       const struct of_phandle_args *sp)
> >   {
> > @@ -310,6 +411,28 @@ static void imx_mu_init_generic(struct
> imx_mu_priv *priv)
> >   	imx_mu_write(priv, 0, priv->dcfg->xCR);
> >   }
> >
> > +static void imx_mu_init_scu(struct imx_mu_priv *priv) {
> > +	unsigned int i;
> > +
> > +	for (i =3D 0; i < IMX_MU_SCU_CHANS; i++) {
> > +		struct imx_mu_con_priv *cp =3D &priv->con_priv[i];
> > +
> > +		cp->idx =3D i < 2 ? 0 : i - 2;
> > +		cp->type =3D i < 2 ? i : IMX_MU_TYPE_RXDB;
> > +		cp->chan =3D &priv->mbox_chans[i];
> > +		priv->mbox_chans[i].con_priv =3D cp;
> > +		snprintf(cp->irq_desc, sizeof(cp->irq_desc),
> > +			 "imx_mu_chan[%i-%i]", cp->type, cp->idx);
> > +	}
> > +
> > +	priv->mbox.num_chans =3D IMX_MU_SCU_CHANS;
> > +	priv->mbox.of_xlate =3D imx_mu_scu_xlate;
> > +
> > +	/* Set default MU configuration */
> > +	imx_mu_write(priv, 0, priv->dcfg->xCR); }
> > +
> >   static int imx_mu_probe(struct platform_device *pdev)
> >   {
> >   	struct device *dev =3D &pdev->dev;
> > @@ -396,9 +519,20 @@ static const struct imx_mu_dcfg
> imx_mu_cfg_imx7ulp =3D {
> >   	.xCR	=3D 0x64,
> >   };
> >
> > +static const struct imx_mu_dcfg imx_mu_cfg_imx8_scu =3D {
> > +	.tx	=3D imx_mu_scu_tx,
> > +	.rx	=3D imx_mu_scu_rx,
> > +	.init	=3D imx_mu_init_scu,
> > +	.xTR	=3D {0x0, 0x4, 0x8, 0xc},
> > +	.xRR	=3D {0x10, 0x14, 0x18, 0x1c},
> > +	.xSR	=3D 0x20,
> > +	.xCR	=3D 0x24,
> > +};
> > +
> >   static const struct of_device_id imx_mu_dt_ids[] =3D {
> >   	{ .compatible =3D "fsl,imx7ulp-mu", .data =3D &imx_mu_cfg_imx7ulp },
> >   	{ .compatible =3D "fsl,imx6sx-mu", .data =3D &imx_mu_cfg_imx6sx },
> > +	{ .compatible =3D "fsl,imx8-mu-scu", .data =3D &imx_mu_cfg_imx8_scu }=
,
> >   	{ },
> >   };
> >   MODULE_DEVICE_TABLE(of, imx_mu_dt_ids);
> >