[PATCH 0/2] amba/serial: amba-pl011: Bring back zx29 UART support

[PATCH 0/2] amba/serial: amba-pl011: Bring back zx29 UART support

[Stefan Dösinger]

This is based on code removed in commit 89d4f98ae90d ("ARM: remove zte
zx platform"). It was previously discussed and reviewed on the 
linux-arm-kernel mailing list as part of my patchset to add initial 
support for ZTE's zx297520v3 router board. I am sending the two UART 
driver patches to linux-serial. The rest goes through the soc list.

Note that the first patch (LLDEBUG) uses a Kconfig symbol introduced by 
my platform patch, which was sent to the soc mailing list. I don't know 
what the correct way to handle this is. I can delay/resend this patchset 
after the soc changes are merged.

Signed-off-by: Stefan Dösinger <stefandoesinger@gmail.com>
---
Stefan Dösinger (2):
      ARM: zte: Add support for zx29 low level debug
      amba/serial: amba-pl011: Bring back zx29 UART support

 arch/arm/Kconfig.debug          | 12 ++++++++++++
 arch/arm/include/debug/pl01x.S  |  9 +++++++++
 drivers/tty/serial/amba-pl011.c | 42 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+)
---
base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
change-id: 20260513-zx29uart-ef44af731390

Best regards,
-- 
Stefan Dösinger <stefandoesinger@gmail.com>

[PATCH 1/2] ARM: zte: Add support for zx29 low level debug

[Stefan Dösinger]

This is based on the removed zx29 code. A separate (more complicated)
patch will re-add the register map to the pl011 serial driver.

Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Stefan Dösinger <stefandoesinger@gmail.com>

---

Patch changelog:
v8: Adjust UART01x_FR_BUSY to match the different ZX UART registers
(Sashiko). I am unsure about UART01x_FR_TXFF and my boards do not expose
flow control pins to allow me to test if it works.

I am unsure about the virtual address. It doesn't seem to matter, as
long as it is a valid address. This address is based on the old removed
code. Is there a rule-of-thumb physical to virtual mapping I can use to
give a sensible default value?
---
 arch/arm/Kconfig.debug         | 12 ++++++++++++
 arch/arm/include/debug/pl01x.S |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 366f162e147d..98d8a5a60048 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -1331,6 +1331,16 @@ choice
 		  This option selects UART0 on VIA/Wondermedia System-on-a-chip
 		  devices, including VT8500, WM8505, WM8650 and WM8850.
 
+	config DEBUG_ZTE_ZX
+		bool "Kernel low-level debugging via zx29 UART"
+		select DEBUG_UART_PL01X
+		depends on ARCH_ZTE
+		help
+		  Say Y here if you are enabling ZTE zx297520v3 SOC and need
+		  debug UART support. This UART is a PL011 with different
+		  register addresses. The UART for boot messages on zx29 boards
+		  is usually UART1 and is operating at 921600 8N1.
+
 	config DEBUG_ZYNQ_UART0
 		bool "Kernel low-level debugging on Xilinx Zynq using UART0"
 		depends on ARCH_ZYNQ
@@ -1545,6 +1555,7 @@ config DEBUG_UART_8250
 
 config DEBUG_UART_PHYS
 	hex "Physical base address of debug UART"
+	default 0x01408000 if DEBUG_ZTE_ZX
 	default 0x01c28000 if DEBUG_SUNXI_UART0
 	default 0x01c28400 if DEBUG_SUNXI_UART1
 	default 0x01d0c000 if DEBUG_DAVINCI_DA8XX_UART1
@@ -1701,6 +1712,7 @@ config DEBUG_UART_VIRT
 	default 0xf31004c0 if DEBUG_MESON_UARTAO
 	default 0xf4090000 if DEBUG_LPC32XX
 	default 0xf4200000 if DEBUG_GEMINI
+	default 0xf4708000 if DEBUG_ZTE_ZX
 	default 0xf6200000 if DEBUG_PXA_UART1
 	default 0xf7000000 if DEBUG_SUN9I_UART0
 	default 0xf7000000 if DEBUG_S3C64XX_UART && DEBUG_S3C_UART0
diff --git a/arch/arm/include/debug/pl01x.S b/arch/arm/include/debug/pl01x.S
index c7e02d0628bf..9dcdeed2357d 100644
--- a/arch/arm/include/debug/pl01x.S
+++ b/arch/arm/include/debug/pl01x.S
@@ -8,6 +8,15 @@
 */
 #include <linux/amba/serial.h>
 
+#ifdef CONFIG_DEBUG_ZTE_ZX
+#undef UART01x_DR
+#undef UART01x_FR
+#undef UART01x_FR_BUSY
+#define UART01x_DR		0x04
+#define UART01x_FR		0x14
+#define UART01x_FR_BUSY		(1<<8)
+#endif
+
 #ifdef CONFIG_DEBUG_UART_PHYS
 		.macro	addruart, rp, rv, tmp
 		ldr	\rp, =CONFIG_DEBUG_UART_PHYS

-- 
2.53.0

[PATCH 2/2] amba/serial: amba-pl011: Bring back zx29 UART support

[Stefan Dösinger]

This is based on code removed in commit 89d4f98ae90d ("ARM: remove zte
zx platform"). I did not bring back the zx29-uart .compatible as the
arm,primecell-periphid does the job.

Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Stefan Dösinger <stefandoesinger@gmail.com>
---

Changes since v4:
Use ZTE's JEDEC ID instead of 0xfe for the DT-Provided AMBA ID.
---
 drivers/tty/serial/amba-pl011.c | 42 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 028e37ad8d79..8ed91e1da22b 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -240,6 +240,38 @@ static struct vendor_data vendor_nvidia = {
 	.get_fifosize		= get_fifosize_nvidia,
 };
 
+static const u16 pl011_zte_offsets[REG_ARRAY_SIZE] = {
+	[REG_DR] = ZX_UART011_DR,
+	[REG_FR] = ZX_UART011_FR,
+	[REG_LCRH_RX] = ZX_UART011_LCRH,
+	[REG_LCRH_TX] = ZX_UART011_LCRH,
+	[REG_IBRD] = ZX_UART011_IBRD,
+	[REG_FBRD] = ZX_UART011_FBRD,
+	[REG_CR] = ZX_UART011_CR,
+	[REG_IFLS] = ZX_UART011_IFLS,
+	[REG_IMSC] = ZX_UART011_IMSC,
+	[REG_RIS] = ZX_UART011_RIS,
+	[REG_MIS] = ZX_UART011_MIS,
+	[REG_ICR] = ZX_UART011_ICR,
+	[REG_DMACR] = ZX_UART011_DMACR,
+};
+
+static unsigned int get_fifosize_zte(struct amba_device *dev)
+{
+	return 16;
+}
+
+static struct vendor_data vendor_zte = {
+	.reg_offset		= pl011_zte_offsets,
+	.access_32b		= true,
+	.ifls			= UART011_IFLS_RX4_8 | UART011_IFLS_TX4_8,
+	.fr_busy		= ZX_UART01x_FR_BUSY,
+	.fr_dsr			= ZX_UART01x_FR_DSR,
+	.fr_cts			= ZX_UART01x_FR_CTS,
+	.fr_ri			= ZX_UART011_FR_RI,
+	.get_fifosize		= get_fifosize_zte,
+};
+
 /* Deals with DMA transactions */
 
 struct pl011_dmabuf {
@@ -3180,6 +3212,16 @@ static const struct amba_id pl011_ids[] = {
 		.mask	= 0x000fffff,
 		.data	= &vendor_nvidia,
 	},
+	{
+		/* This is an invented ID. The actual hardware that contains
+		 * these ZTE UARTs (zx29 boards) has no AMBA PIDs stored. ZTE
+		 * JEDEC ID (ignoring banks) and the "011" part number as used
+		 * by ARM.
+		 */
+		.id	= 0x0008c011,
+		.mask	= 0x000fffff,
+		.data	= &vendor_zte,
+	},
 	{ 0, 0 },
 };
 

-- 
2.53.0