linux-kernel - Re: [PATCH v6 2/2] tty: samsung_tty: 32-bit access for TX/RX hold registers

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Date:   Tue, 7 Apr 2020 09:22:21 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     Hyunki Koo <hyunki00.koo@...sung.com>, gregkh@...uxfoundation.org,
        Rob Herring <robh+dt@...nel.org>,
        Kukjin Kim <kgene@...nel.org>, linux-serial@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v6 2/2] tty: samsung_tty: 32-bit access for TX/RX hold
 registers

On Tue, Apr 07, 2020 at 08:32:56AM +0200, Jiri Slaby wrote:
> On 07. 04. 20, 8:24, Krzysztof Kozlowski wrote:
> > On Tue, Apr 07, 2020 at 06:49:29AM +0200, Jiri Slaby wrote:
> >> On 07. 04. 20, 1:08, 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 <hyunki00.koo@...sung.com>
> >> ...
> >>> ---
> >>>  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 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)
> >>
> >> You need to explain, why you need this _barrier variant now. This change
> >> should be done in a separate patch too.
> > 
> > There is no functional change in regard of barrier.  The ordered IO was
> > used there before.
> 
> The patch changes one wr_reg to wr_reg_barrier without any explanation.
> This will hardly be accepted.

I cannot find such change... I see only:

@@ -2612,7 +2664,7 @@ static void samsung_early_putc(struct uart_port *port, int c)
-       writeb(c, port->membase + S3C2410_UTXH);
+       wr_reg_barrier(port, S3C2410_UTXH, c);

which is the same except 'b' -> 'b/l'.

Best regards,
Krzysztof