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

From: Greg KH <[email-masked]>
Date: Fri, 3 Apr 2020 13:57:15 +0200

On Fri, Apr 03, 2020 at 01:53:13PM +0200, Krzysztof Kozlowski wrote:
> On Fri, Apr 03, 2020 at 01:42:37PM +0200, Greg KH 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;
> > > +	}
> > > +}
> > 
> > why do you have a default for the read function, but not the write
> > functions?
> 
> The default for read will never happen and it returns bogus value just
> to satisfy the compiler. That's my understanding. What would you like to
> do for writes()? Print error msg? No point, it should not happen because
> of check in probe().

Consistancy please, either do it for all, or none, otherwise it makes no
sense at all.

> > > +
> > >  /* 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) {
> > > +			switch (prop) {
> > > +			case 1:
> > > +				ourport->port.iotype = UPIO_MEM;
> > > +				break;
> > > +			case 4:
> > > +				ourport->port.iotype = UPIO_MEM32;
> > > +				break;
> > > +			default:
> > > +				dev_warn(&pdev->dev, "unsupported reg-io-width (%d)\n",
> > > +						prop);
> > > +				ret = -EINVAL;
> > > +				break;
> > > +			}
> > > +		}
> > > +	}
> > 
> > If the property is not there, the type will be uninitialized and no
> > warning will be spit out, are you sure you want to do that?
> 
> The default value from initial ourport will be used, which is UPIO_MEM.
> This way it is backward compatible.

Where is iotype set to UPIO_MEM as a default?

thanks,

greg k-h

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