Subject: RE: [PATCH v4] tty: samsung_tty: 32-bit access for TX/RX hold registers

From: "Hyunki Koo" <[email-masked]>
Date: Mon, 6 Apr 2020 06:41:09 +0900

On Fri, Apr 03, 2020 at 10:35:10PM +0900, Krzysztof Kozlowski wrote:
> On Fri, Apr 03, 2020 at 08:15:10PM +0900, Hyunki Koo wrote:
> > Support 32-bit access for the TX/RX hold registers UTXH and URXH.
> >
> > This is required for some newer SoCs.
> >
> > Signed-off-by: Hyunki Koo <[email-masked]>
> > ---
> > v2:
> > line 954 : change rd_regl to rd_reg in for backward compatibility.
> > line 2031: Add init value for ourport->port.iotype  to UPIO_MEM
> > v3:
> > line 2031: remove redundant init value  for ourport->port.iotype
> > v4:
> > correct variable types and change misleading function name
> > ---
> >  drivers/tty/serial/samsung_tty.c | 76
> > +++++++++++++++++++++++++++++++++-------
> >  1 file changed, 64 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/tty/serial/samsung_tty.c
> > b/drivers/tty/serial/samsung_tty.c
> > index 73f951d65b93..bdf1d4d12cb1 100644
> > --- a/drivers/tty/serial/samsung_tty.c
> > +++ b/drivers/tty/serial/samsung_tty.c
> > @@ -154,12 +154,47 @@ struct s3c24xx_uart_port {  #define
> > portaddrl(port, reg) \
> >  	((unsigned long *)(unsigned long)((port)->membase + (reg)))
> >
> > -#define rd_regb(port, reg) (readb_relaxed(portaddr(port, reg)))
> > +static u32 rd_reg(struct uart_port *port, u32 reg) {
> > +	switch (port->iotype) {
> > +	case UPIO_MEM:
> > +		return readb_relaxed(portaddr(port, reg));
> > +	case UPIO_MEM32:
> > +		return readl_relaxed(portaddr(port, reg));
> > +	default:
> > +		return 0;
> > +	}
> > +	return 0;
> > +}
> > +
> >  #define rd_regl(port, reg) (readl_relaxed(portaddr(port, reg)))
> >
> > -#define wr_regb(port, reg, val) writeb_relaxed(val, portaddr(port,
> > reg))
> > +static void wr_reg(struct uart_port *port, u32 reg, u32 val) {
> > +	switch (port->iotype) {
> > +	case UPIO_MEM:
> > +		writeb_relaxed(val, portaddr(port, reg));
> > +		break;
> > +	case UPIO_MEM32:
> > +		writel_relaxed(val, portaddr(port, reg));
> > +		break;
> > +	}
> > +}
> > +
> >  #define wr_regl(port, reg, val) writel_relaxed(val, portaddr(port,
> > reg))
> >
> > +static void wr_reg_barrier(struct uart_port *port, u32 reg, u32 val)
> > +{
> > +	switch (port->iotype) {
> > +	case UPIO_MEM:
> > +		writeb(val, portaddr(port, reg));
> > +		break;
> > +	case UPIO_MEM32:
> > +		writel(val, portaddr(port, reg));
> > +		break;
> > +	}
> > +}
> > +
> >  /* Byte-order aware bit setting/clearing functions. */
> >
> >  static inline void s3c24xx_set_bit(struct uart_port *port, int idx,
> > @@ -714,7 +749,7 @@ static void s3c24xx_serial_rx_drain_fifo(struct
> s3c24xx_uart_port *ourport)
> >  		fifocnt--;
> >
> >  		uerstat = rd_regl(port, S3C2410_UERSTAT);
> > -		ch = rd_regb(port, S3C2410_URXH);
> > +		ch = rd_reg(port, S3C2410_URXH);
> >
> >  		if (port->flags & UPF_CONS_FLOW) {
> >  			int txe = s3c24xx_serial_txempty_nofifo(port);
> > @@ -826,7 +861,7 @@ static irqreturn_t s3c24xx_serial_tx_chars(int
> irq, void *id)
> >  	}
> >
> >  	if (port->x_char) {
> > -		wr_regb(port, S3C2410_UTXH, port->x_char);
> > +		wr_reg(port, S3C2410_UTXH, port->x_char);
> >  		port->icount.tx++;
> >  		port->x_char = 0;
> >  		goto out;
> > @@ -852,7 +887,7 @@ static irqreturn_t s3c24xx_serial_tx_chars(int
> irq, void *id)
> >  		if (rd_regl(port, S3C2410_UFSTAT) & ourport->info-
> >tx_fifofull)
> >  			break;
> >
> > -		wr_regb(port, S3C2410_UTXH, xmit->buf[xmit->tail]);
> > +		wr_reg(port, S3C2410_UTXH, xmit->buf[xmit->tail]);
> >  		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
> >  		port->icount.tx++;
> >  		count--;
> > @@ -916,7 +951,7 @@ static unsigned int
> s3c24xx_serial_tx_empty(struct
> > uart_port *port)
> >  /* no modem control lines */
> >  static unsigned int s3c24xx_serial_get_mctrl(struct uart_port *port)
> > {
> > -	unsigned int umstat = rd_regb(port, S3C2410_UMSTAT);
> > +	unsigned int umstat = rd_reg(port, S3C2410_UMSTAT);
> >
> >  	if (umstat & S3C2410_UMSTAT_CTS)
> >  		return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS; @@ -
> 1974,7 +2009,7 @@
> > static int s3c24xx_serial_probe(struct platform_device *pdev)
> >  	struct device_node *np = pdev->dev.of_node;
> >  	struct s3c24xx_uart_port *ourport;
> >  	int index = probe_index;
> > -	int ret;
> > +	int ret, prop = 0;
> >
> >  	if (np) {
> >  		ret = of_alias_get_id(np, "serial"); @@ -2000,10
> +2035,27 @@ static
> > int s3c24xx_serial_probe(struct platform_device *pdev)
> >  			dev_get_platdata(&pdev->dev) :
> >  			ourport->drv_data->def_cfg;
> >
> > -	if (np)
> > +	if (np) {
> >  		of_property_read_u32(np,
> >  			"samsung,uart-fifosize", &ourport->port.fifosize);
> >
> > +		if (of_property_read_u32(np, "reg-io-width", &prop) ==
> 0) {
> 
> I got more thoughts... where is the binding for it? It looked like standard
> DT property but it is not described in device tree spec.
> 
> Also, where is the user (DTS) with it? I expect such changes go with the
> user itself... otherwise, next cleanup it will go away.
> 
> Best regards,
> Krzysztof

Do you think this kind of change is needed?
Do I have to make as a series patches with previous patch?

diff --git a/Documentation/devicetree/bindings/serial/samsung_uart.yaml b/Documentation/devicetree/bindings/serial/samsung_uart.yaml
index 9d2ce347875b..a57b1233c691 100644
--- a/Documentation/devicetree/bindings/serial/samsung_uart.yaml
+++ b/Documentation/devicetree/bindings/serial/samsung_uart.yaml
@@ -29,6 +29,14 @@ properties:
   reg:
     maxItems: 1
 
+  reg-io-width:
+    description: |
+      The size (in bytes) of the IO accesses that should be performed
+      on the device.
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+      - enum: [ 1, 4 ]
+

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