[RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5

[RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5

[Jongsung Kim]

The latest r1p5-revision of the ARM PL011 UART has 32-byte FIFOs,
while all earlier ones have 16-byte FIFOs. This patch suggests
a way to set the FIFO-size correctly & flexibly by using a member
function named get_fifosize, rather than using the fifosize member
variable. The function takes the UARTPeriphID, and returns the
correct FIFO size.

Signed-off-by: Jongsung Kim <neidhard.kim@lge.com>
---
 drivers/tty/serial/amba-pl011.c |   20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 3ea5408..22af0c8 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -72,32 +72,44 @@
 /* There is by now at least one vendor with differing details, so handle it */
 struct vendor_data {
 	unsigned int		ifls;
-	unsigned int		fifosize;
 	unsigned int		lcrh_tx;
 	unsigned int		lcrh_rx;
 	bool			oversampling;
 	bool			dma_threshold;
 	bool			cts_event_workaround;
+
+	unsigned int (*get_fifosize)(unsigned int periphid);
 };
 
+static unsigned int get_fifosize_arm(unsigned int periphid)
+{
+	unsigned int rev = (periphid >> 20) & 0xf;
+	return rev < 3 ? 16 : 32;
+}
+
 static struct vendor_data vendor_arm = {
 	.ifls			= UART011_IFLS_RX4_8|UART011_IFLS_TX4_8,
-	.fifosize		= 16,
 	.lcrh_tx		= UART011_LCRH,
 	.lcrh_rx		= UART011_LCRH,
 	.oversampling		= false,
 	.dma_threshold		= false,
 	.cts_event_workaround	= false,
+	.get_fifosize		= get_fifosize_arm,
 };
 
+static unsigned int get_fifosize_st(unsigned int periphid)
+{
+	return 64;
+}
+
 static struct vendor_data vendor_st = {
 	.ifls			= UART011_IFLS_RX_HALF|UART011_IFLS_TX_HALF,
-	.fifosize		= 64,
 	.lcrh_tx		= ST_UART011_LCRH_TX,
 	.lcrh_rx		= ST_UART011_LCRH_RX,
 	.oversampling		= true,
 	.dma_threshold		= true,
 	.cts_event_workaround	= true,
+	.get_fifosize		= get_fifosize_st,
 };
 
 static struct uart_amba_port *amba_ports[UART_NR];
@@ -2010,7 +2022,7 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 	uap->lcrh_rx = vendor->lcrh_rx;
 	uap->lcrh_tx = vendor->lcrh_tx;
 	uap->old_cr = 0;
-	uap->fifosize = vendor->fifosize;
+	uap->fifosize = vendor->get_fifosize(dev->periphid);
 	uap->port.dev = &dev->dev;
 	uap->port.mapbase = dev->res.start;
 	uap->port.membase = base;

Re: [RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5

[Russell King - ARM Linux]

On Mon, Apr 15, 2013 at 02:45:25PM +0900, Jongsung Kim wrote:
> The latest r1p5-revision of the ARM PL011 UART has 32-byte FIFOs,
> while all earlier ones have 16-byte FIFOs. This patch suggests
> a way to set the FIFO-size correctly & flexibly by using a member
> function named get_fifosize, rather than using the fifosize member
> variable. The function takes the UARTPeriphID, and returns the
> correct FIFO size.

Same comments as previous version.

Re: [RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5

[Linus Walleij]

On Mon, Apr 15, 2013 at 7:45 AM, Jongsung Kim <neidhard.kim@lge.com> wrote:

At the risk to re-stating what Russell has already said...

> +
> +       unsigned int (*get_fifosize)(unsigned int periphid);
>  };
>
> +static unsigned int get_fifosize_arm(unsigned int periphid)
> +{
> +       unsigned int rev = (periphid >> 20) & 0xf;
> +       return rev < 3 ? 16 : 32;
> +}

This is a very complicated way to to something very simple.

Keep the .fifosize as part of struct vendor_data, define a
new vendor data cunk for your variant, use .id and .mask
to select your variant.

static struct vendor_data vendor_arm_deepfifo = {
     .fifosize = 32,
     (... the rest is the same)
}

(...)

static struct amba_id pl011_ids[] = {
        {
                .id     = 0x00341011,
                .mask   = 0x00ffffff,
                .data   = &vendor_arm_deepfifo,
        },
(...)
};

As you can see in amba_lookup() in
drivers/amba/bus.c the table is traversed from the top,
so for the new "3" variant this entry will match, while the
next entry will match all older versions.

Yours,
Linus Walleij

Re: [RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5

[Russell King - ARM Linux]

On Sat, Apr 20, 2013 at 03:31:39PM +0200, Linus Walleij wrote:
> static struct amba_id pl011_ids[] = {
>         {
>                 .id     = 0x00341011,
>                 .mask   = 0x00ffffff,
>                 .data   = &vendor_arm_deepfifo,
>         },
> (...)
> };
> 
> As you can see in amba_lookup() in
> drivers/amba/bus.c the table is traversed from the top,
> so for the new "3" variant this entry will match, while the
> next entry will match all older versions.

This isn't equivalent - this will only match variant 3, not any later
ones.  The original patch uses the deep fifo for variant 3 or larger.

RE: [RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5

[Jongsung Kim]

Thank you for your comments, Russell. I'll happily apply your recommendation
just after it come up to the merge window. Or, do you want me to send it by now?

-----Original Message-----
From: Russell King - ARM Linux [mailto:linux@arm.linux.org.uk] 
Sent: Friday, April 19, 2013 11:18 PM
To: Jongsung Kim
Cc: gregkh@linuxfoundation.org; jslaby@suse.cz; linux-serial@vger.kernel.org;
linux-kernel@vger.kernel.org
Subject: Re: [RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of
PL011-r1p5

On Mon, Apr 15, 2013 at 02:45:25PM +0900, Jongsung Kim wrote:
> The latest r1p5-revision of the ARM PL011 UART has 32-byte FIFOs,
> while all earlier ones have 16-byte FIFOs. This patch suggests
> a way to set the FIFO-size correctly & flexibly by using a member
> function named get_fifosize, rather than using the fifosize member
> variable. The function takes the UARTPeriphID, and returns the
> correct FIFO size.

Same comments as previous version.

Re: [RESEND][PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5

[Russell King - ARM Linux]

On Mon, Apr 22, 2013 at 11:24:18AM +0900, Jongsung Kim wrote:
> Thank you for your comments, Russell. I'll happily apply your recommendation
> just after it come up to the merge window. Or, do you want me to send it by
> now?

Sorry, don't understand what you're asking, could you rephrase please?