On Thu, Jul 07, 2016 at 11:01:07PM +0800, Shawn Guo wrote:

On Thu, Jul 07, 2016 at 05:54:53PM +0800, Shawn Guo wrote:

quoted

I think this version of the patch is trying to address the comment you
put on v1, i.e. instead of extending platform driver we should try to
probe ZTE UART from AMBA bus.

The solution here is to fake a AMBA peripheral ID which does not exist
on hardware with a magic number.  While it's working, it looks too
hackish, and doesn't really scale in the long run.  I hope that's also
the reason you are unwilling to provide your ACK :)

Unless you have a better solution to suggest, I would think that
platform driver is a sensible way to support the device, and will go
back to v1 approach.

Just found that Russell's email address changed.  Resend to the new
address.

So, if I were to do this, there wouldn't be any objection?

An alternative would be to use the real hardware ID if it exists, add
a compatible to DT, and use of_device_is_compatible() in the driver
to discover if it's a zte device.

8<====
Subject: [PATCH] amba: make ZTE pseudo-ID more "official"

Signed-off-by: Russell King <redacted>
---
 drivers/tty/serial/amba-pl011.c | 4 ++--
 include/linux/amba/bus.h        | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 77b05f5bf866..2dbe5776ac56 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c

@@ -2659,8 +2659,8 @@ static struct amba_id pl011_ids[] = {
 		.data	= &vendor_st,
 	},
 	{
-		.id	= 0xfefefe,
-		.mask	= 0xffffff,
+		.id	= AMBA_LINUX_ID(0x00, 0xf, 0xefe),
+		.mask	= 0x00ffffff,
 		.data	= &vendor_zte,
 	},
 	{ 0, 0 },

diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h
index 3d8dcdd1aeae..dc29d504b4fc 100644
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h

@@ -53,8 +53,13 @@ enum amba_vendor {
 	AMBA_VENDOR_ST = 0x80,
 	AMBA_VENDOR_QCOM = 0x51,
 	AMBA_VENDOR_LSI = 0xb6,
+	AMBA_VENDOR_LINUX = 0xef,	/* This value is not official */
 };
 
+#define AMBA_LINUX_ID(conf, rev, part) \
+	(((conf) & 0xff) << 24 | ((rev) & 0xf) << 20 | \
+	 AMBA_VENDOR_LINUX << 12 | ((part) & 0xfff))
+
 extern struct bus_type amba_bustype;
 
 #define to_amba_device(d)	container_of(d, struct amba_device, dev)

-- 
2.1.0

-- 
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