[PATCH v4 0/4] serial: 8250_dw: Add support for UltraRISC DP1000 UART

[PATCH v4 0/4] serial: 8250_dw: Add support for UltraRISC DP1000 UART

[Jia Wang]

This patch series adds support for the UltraRISC DP1000 UART controller.

The series includes four patches. The first two are preparatory cleanups;
the last two add the DP1000 compatible and fixed CPR handling.

The patches have been tested on an UltraRISC DP1000 development board with
Linux v7.0-rc7, verifying basic UART functionality.

Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
---
Changes in v4:
- Added two preparatory patches before the original series, shifting patch
  numbers (former 1/2 -> now 3/4).
- Patch 1:
  * Move all DesignWare UART register/field definitions into 8250_dwlib.h
    for shared use with 8250_dw.
- Patch 2:
  * Converted the Renesas RZ/N1 CPR magic value to use DW_UART_CPR_* macros
    and FIELD_PREP_CONST().
- Patch 4:
  * Converted the UltraRISC DP1000 CPR magic value to use
    DW_UART_CPR_* macros and FIELD_PREP_CONST() (value unchanged).
- Link to v3: https://patch.msgid.link/20260421-ultrarisc-serial-v3-0-3d7f09c2420e@ultrarisc.com

Changes in v3:
- Rebased on Linux v7.0-rc7.
- Patch 1:
   * Removed separate `items` entry for DP1000, merging it into the
     existing `enum` to comply with the schema.
   * Updated commit message to describe DP1000 UART hardware differences.
- Patch 2:
   * Drop the custom quirk for missing CPR register.
   * Switch to using DW_UART_QUIRK_CPR_VALUE to provide a fixed CPR value.
- Link to v2: https://patch.msgid.link/20260316-ultrarisc-serial-v2-0-6ab3e7fa891c@ultrarisc.com

Changes in v2:
- Rebased on Linux v7.0-rc4 (previously on v7.0-rc2).
- Reordered patch series: DT binding patch comes before driver changes.
- Updated commit message for DT binding patch.
- Link to v1: https://patch.msgid.link/20260316-ultrarisc-serial-v1-0-c464f3e933a5@ultrarisc.com

---
Jia Wang (4):
      serial: 8250_dwlib: move DesignWare register definitions to header
      serial: 8250_dw: build Renesas RZN1 CPR value from DW_UART_CPR_* definitions
      dt-bindings: serial: snps-dw-apb-uart: Add UltraRISC DP1000 UART
      serial: 8250_dw: Use a fixed CPR value for UltraRISC DP1000 UART

 .../bindings/serial/snps-dw-apb-uart.yaml          |  1 +
 drivers/tty/serial/8250/8250_dw.c                  | 31 ++++++-----
 drivers/tty/serial/8250/8250_dwlib.c               | 49 -----------------
 drivers/tty/serial/8250/8250_dwlib.h               | 63 ++++++++++++++++++++++
 4 files changed, 83 insertions(+), 61 deletions(-)
---
base-commit: e774d5f1bc27a85f858bce7688509e866f8e8a4e
change-id: 20260309-ultrarisc-serial-64ff637edf26

Best regards,
--  
Jia Wang <wangjia@ultrarisc.com>

[PATCH v4 1/4] serial: 8250_dwlib: move DesignWare register definitions to header

[Jia Wang]

Move the DW_UART_* register offsets and CPR bit/field definitions from
8250_dwlib.c into 8250_dwlib.h so they can be shared by 8250_dw and
8250_dwlib users.

Add an include guard for 8250_dwlib.h.

Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
---
 drivers/tty/serial/8250/8250_dw.c    | 11 -------
 drivers/tty/serial/8250/8250_dwlib.c | 49 ----------------------------
 drivers/tty/serial/8250/8250_dwlib.h | 63 ++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 60 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 94beadb4024d..467755bf0092 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -34,22 +34,11 @@
 
 #include "8250_dwlib.h"
 
-/* Offsets for the DesignWare specific registers */
-#define DW_UART_USR	0x1f /* UART Status Register */
-#define DW_UART_DMASA	0xa8 /* DMA Software Ack */
-
 #define OCTEON_UART_USR	0x27 /* UART Status Register */
 
 #define RZN1_UART_TDMACR 0x10c /* DMA Control Register Transmit Mode */
 #define RZN1_UART_RDMACR 0x110 /* DMA Control Register Receive Mode */
 
-/* DesignWare specific register fields */
-#define DW_UART_IIR_IID			GENMASK(3, 0)
-
-#define DW_UART_MCR_SIRE		BIT(6)
-
-#define DW_UART_USR_BUSY		BIT(0)
-
 /* Renesas specific register fields */
 #define RZN1_UART_xDMACR_DMA_EN		BIT(0)
 #define RZN1_UART_xDMACR_1_WORD_BURST	(0 << 1)
diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c
index b055d89cfb39..8859e66d2d71 100644
--- a/drivers/tty/serial/8250/8250_dwlib.c
+++ b/drivers/tty/serial/8250/8250_dwlib.c
@@ -13,55 +13,6 @@
 
 #include "8250_dwlib.h"
 
-/* Offsets for the DesignWare specific registers */
-#define DW_UART_TCR	0xac /* Transceiver Control Register (RS485) */
-#define DW_UART_DE_EN	0xb0 /* Driver Output Enable Register */
-#define DW_UART_RE_EN	0xb4 /* Receiver Output Enable Register */
-#define DW_UART_DLF	0xc0 /* Divisor Latch Fraction Register */
-#define DW_UART_RAR	0xc4 /* Receive Address Register */
-#define DW_UART_TAR	0xc8 /* Transmit Address Register */
-#define DW_UART_LCR_EXT	0xcc /* Line Extended Control Register */
-#define DW_UART_CPR	0xf4 /* Component Parameter Register */
-#define DW_UART_UCV	0xf8 /* UART Component Version */
-
-/* Receive / Transmit Address Register bits */
-#define DW_UART_ADDR_MASK		GENMASK(7, 0)
-
-/* Line Status Register bits */
-#define DW_UART_LSR_ADDR_RCVD		BIT(8)
-
-/* Transceiver Control Register bits */
-#define DW_UART_TCR_RS485_EN		BIT(0)
-#define DW_UART_TCR_RE_POL		BIT(1)
-#define DW_UART_TCR_DE_POL		BIT(2)
-#define DW_UART_TCR_XFER_MODE		GENMASK(4, 3)
-#define DW_UART_TCR_XFER_MODE_DE_DURING_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 0)
-#define DW_UART_TCR_XFER_MODE_SW_DE_OR_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 1)
-#define DW_UART_TCR_XFER_MODE_DE_OR_RE		FIELD_PREP(DW_UART_TCR_XFER_MODE, 2)
-
-/* Line Extended Control Register bits */
-#define DW_UART_LCR_EXT_DLS_E		BIT(0)
-#define DW_UART_LCR_EXT_ADDR_MATCH	BIT(1)
-#define DW_UART_LCR_EXT_SEND_ADDR	BIT(2)
-#define DW_UART_LCR_EXT_TRANSMIT_MODE	BIT(3)
-
-/* Component Parameter Register bits */
-#define DW_UART_CPR_ABP_DATA_WIDTH	GENMASK(1, 0)
-#define DW_UART_CPR_AFCE_MODE		BIT(4)
-#define DW_UART_CPR_THRE_MODE		BIT(5)
-#define DW_UART_CPR_SIR_MODE		BIT(6)
-#define DW_UART_CPR_SIR_LP_MODE		BIT(7)
-#define DW_UART_CPR_ADDITIONAL_FEATURES	BIT(8)
-#define DW_UART_CPR_FIFO_ACCESS		BIT(9)
-#define DW_UART_CPR_FIFO_STAT		BIT(10)
-#define DW_UART_CPR_SHADOW		BIT(11)
-#define DW_UART_CPR_ENCODED_PARMS	BIT(12)
-#define DW_UART_CPR_DMA_EXTRA		BIT(13)
-#define DW_UART_CPR_FIFO_MODE		GENMASK(23, 16)
-
-/* Helper for FIFO size calculation */
-#define DW_UART_CPR_FIFO_SIZE(a)	(FIELD_GET(DW_UART_CPR_FIFO_MODE, (a)) * 16)
-
 /*
  * divisor = div(I) + div(F)
  * "I" means integer, "F" means fractional
diff --git a/drivers/tty/serial/8250/8250_dwlib.h b/drivers/tty/serial/8250/8250_dwlib.h
index 7dd2a8e7b780..5026a123cf42 100644
--- a/drivers/tty/serial/8250/8250_dwlib.h
+++ b/drivers/tty/serial/8250/8250_dwlib.h
@@ -1,11 +1,72 @@
 /* SPDX-License-Identifier: GPL-2.0+ */
 /* Synopsys DesignWare 8250 library header file. */
 
+#ifndef _SERIAL_8250_DWLIB_H_
+#define _SERIAL_8250_DWLIB_H_
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
 #include <linux/io.h>
 #include <linux/types.h>
 
 #include "8250.h"
 
+/* Offsets for the DesignWare specific registers */
+#define DW_UART_USR	0x1f /* UART Status Register */
+#define DW_UART_DMASA	0xa8 /* DMA Software Ack */
+#define DW_UART_TCR	0xac /* Transceiver Control Register (RS485) */
+#define DW_UART_DE_EN	0xb0 /* Driver Output Enable Register */
+#define DW_UART_RE_EN	0xb4 /* Receiver Output Enable Register */
+#define DW_UART_DLF	0xc0 /* Divisor Latch Fraction Register */
+#define DW_UART_RAR	0xc4 /* Receive Address Register */
+#define DW_UART_TAR	0xc8 /* Transmit Address Register */
+#define DW_UART_LCR_EXT	0xcc /* Line Extended Control Register */
+#define DW_UART_CPR	0xf4 /* Component Parameter Register */
+#define DW_UART_UCV	0xf8 /* UART Component Version */
+
+/* Receive / Transmit Address Register bits */
+#define DW_UART_ADDR_MASK		GENMASK(7, 0)
+
+/* Line Status Register bits */
+#define DW_UART_LSR_ADDR_RCVD		BIT(8)
+
+/* Transceiver Control Register bits */
+#define DW_UART_TCR_RS485_EN		BIT(0)
+#define DW_UART_TCR_RE_POL		BIT(1)
+#define DW_UART_TCR_DE_POL		BIT(2)
+#define DW_UART_TCR_XFER_MODE		GENMASK(4, 3)
+#define DW_UART_TCR_XFER_MODE_DE_DURING_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 0)
+#define DW_UART_TCR_XFER_MODE_SW_DE_OR_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 1)
+#define DW_UART_TCR_XFER_MODE_DE_OR_RE		FIELD_PREP(DW_UART_TCR_XFER_MODE, 2)
+
+/* Line Extended Control Register bits */
+#define DW_UART_LCR_EXT_DLS_E		BIT(0)
+#define DW_UART_LCR_EXT_ADDR_MATCH	BIT(1)
+#define DW_UART_LCR_EXT_SEND_ADDR	BIT(2)
+#define DW_UART_LCR_EXT_TRANSMIT_MODE	BIT(3)
+
+/* Component Parameter Register bits */
+#define DW_UART_CPR_ABP_DATA_WIDTH	GENMASK(1, 0)
+#define DW_UART_CPR_AFCE_MODE		BIT(4)
+#define DW_UART_CPR_THRE_MODE		BIT(5)
+#define DW_UART_CPR_SIR_MODE		BIT(6)
+#define DW_UART_CPR_SIR_LP_MODE		BIT(7)
+#define DW_UART_CPR_ADDITIONAL_FEATURES	BIT(8)
+#define DW_UART_CPR_FIFO_ACCESS		BIT(9)
+#define DW_UART_CPR_FIFO_STAT		BIT(10)
+#define DW_UART_CPR_SHADOW		BIT(11)
+#define DW_UART_CPR_ENCODED_PARMS	BIT(12)
+#define DW_UART_CPR_DMA_EXTRA		BIT(13)
+#define DW_UART_CPR_FIFO_MODE		GENMASK(23, 16)
+
+/* DesignWare specific register fields */
+#define DW_UART_IIR_IID			GENMASK(3, 0)
+#define DW_UART_MCR_SIRE		BIT(6)
+#define DW_UART_USR_BUSY		BIT(0)
+
+/* Helper for FIFO size calculation */
+#define DW_UART_CPR_FIFO_SIZE(a)	(FIELD_GET(DW_UART_CPR_FIFO_MODE, (a)) * 16)
+
 struct dw8250_port_data {
 	/* Port properties */
 	int			line;
@@ -38,3 +99,5 @@ static inline void dw8250_writel_ext(struct uart_port *p, int offset, u32 reg)
 	else
 		writel(reg, p->membase + offset);
 }
+
+#endif /* _SERIAL_8250_DWLIB_H_ */

-- 
2.34.1

Re: [PATCH v4 1/4] serial: 8250_dwlib: move DesignWare register definitions to header

[Andy Shevchenko]

On Fri, Apr 24, 2026 at 01:39:28PM +0800, Jia Wang wrote:
> Move the DW_UART_* register offsets and CPR bit/field definitions from
> 8250_dwlib.c into 8250_dwlib.h so they can be shared by 8250_dw and
> 8250_dwlib users.
> 
> Add an include guard for 8250_dwlib.h.

...

> -/* DesignWare specific register fields */
> -#define DW_UART_IIR_IID			GENMASK(3, 0)
> -
> -#define DW_UART_MCR_SIRE		BIT(6)
> -
> -#define DW_UART_USR_BUSY		BIT(0)
> -

One nit-pick, though, these three need the similar comments in the header and a
blank line between them.

...

> +/* Offsets for the DesignWare specific registers */
> +#define DW_UART_USR	0x1f /* UART Status Register */
> +#define DW_UART_DMASA	0xa8 /* DMA Software Ack */
> +#define DW_UART_TCR	0xac /* Transceiver Control Register (RS485) */
> +#define DW_UART_DE_EN	0xb0 /* Driver Output Enable Register */
> +#define DW_UART_RE_EN	0xb4 /* Receiver Output Enable Register */
> +#define DW_UART_DLF	0xc0 /* Divisor Latch Fraction Register */
> +#define DW_UART_RAR	0xc4 /* Receive Address Register */
> +#define DW_UART_TAR	0xc8 /* Transmit Address Register */
> +#define DW_UART_LCR_EXT	0xcc /* Line Extended Control Register */
> +#define DW_UART_CPR	0xf4 /* Component Parameter Register */
> +#define DW_UART_UCV	0xf8 /* UART Component Version */
> +
> +/* Receive / Transmit Address Register bits */
> +#define DW_UART_ADDR_MASK		GENMASK(7, 0)

> +/* Line Status Register bits */
> +#define DW_UART_LSR_ADDR_RCVD		BIT(8)

Like this one, the IIR. MCR, and USR bits should be commented. Also preserve
the sorting by the register offset, so the groups of bits follow the above list
of registers, where USR bits, for example, should go before TCR.

> +/* Transceiver Control Register bits */
> +#define DW_UART_TCR_RS485_EN		BIT(0)
> +#define DW_UART_TCR_RE_POL		BIT(1)
> +#define DW_UART_TCR_DE_POL		BIT(2)
> +#define DW_UART_TCR_XFER_MODE		GENMASK(4, 3)
> +#define DW_UART_TCR_XFER_MODE_DE_DURING_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 0)
> +#define DW_UART_TCR_XFER_MODE_SW_DE_OR_RE	FIELD_PREP(DW_UART_TCR_XFER_MODE, 1)
> +#define DW_UART_TCR_XFER_MODE_DE_OR_RE		FIELD_PREP(DW_UART_TCR_XFER_MODE, 2)
> +
> +/* Line Extended Control Register bits */
> +#define DW_UART_LCR_EXT_DLS_E		BIT(0)
> +#define DW_UART_LCR_EXT_ADDR_MATCH	BIT(1)
> +#define DW_UART_LCR_EXT_SEND_ADDR	BIT(2)
> +#define DW_UART_LCR_EXT_TRANSMIT_MODE	BIT(3)
> +
> +/* Component Parameter Register bits */
> +#define DW_UART_CPR_ABP_DATA_WIDTH	GENMASK(1, 0)
> +#define DW_UART_CPR_AFCE_MODE		BIT(4)
> +#define DW_UART_CPR_THRE_MODE		BIT(5)
> +#define DW_UART_CPR_SIR_MODE		BIT(6)
> +#define DW_UART_CPR_SIR_LP_MODE		BIT(7)
> +#define DW_UART_CPR_ADDITIONAL_FEATURES	BIT(8)
> +#define DW_UART_CPR_FIFO_ACCESS		BIT(9)
> +#define DW_UART_CPR_FIFO_STAT		BIT(10)
> +#define DW_UART_CPR_SHADOW		BIT(11)
> +#define DW_UART_CPR_ENCODED_PARMS	BIT(12)
> +#define DW_UART_CPR_DMA_EXTRA		BIT(13)
> +#define DW_UART_CPR_FIFO_MODE		GENMASK(23, 16)

> +/* DesignWare specific register fields */
> +#define DW_UART_IIR_IID			GENMASK(3, 0)
> +#define DW_UART_MCR_SIRE		BIT(6)
> +#define DW_UART_USR_BUSY		BIT(0)

I.o.w. uncouple these as per above.

-- 
With Best Regards,
Andy Shevchenko

[PATCH v4 2/4] serial: 8250_dw: build Renesas RZN1 CPR value from DW_UART_CPR_* definitions

[Jia Wang]

Replace the magic CPR value for Renesas RZ/N1 with a composition using
DW_UART_CPR_* bit/field definitions and FIELD_PREP_CONST().

Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
---
 drivers/tty/serial/8250/8250_dw.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 467755bf0092..d3c2c9c84d9f 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -937,7 +937,15 @@ static const struct dw8250_platform_data dw8250_armada_38x_data = {
 
 static const struct dw8250_platform_data dw8250_renesas_rzn1_data = {
 	.usr_reg = DW_UART_USR,
-	.cpr_value = 0x00012f32,
+	.cpr_value = FIELD_PREP_CONST(DW_UART_CPR_ABP_DATA_WIDTH, 2) |
+		     DW_UART_CPR_AFCE_MODE |
+		     DW_UART_CPR_THRE_MODE |
+		     DW_UART_CPR_ADDITIONAL_FEATURES |
+		     DW_UART_CPR_FIFO_ACCESS |
+		     DW_UART_CPR_FIFO_STAT |
+		     DW_UART_CPR_SHADOW |
+		     DW_UART_CPR_DMA_EXTRA |
+		     FIELD_PREP_CONST(DW_UART_CPR_FIFO_MODE, 0x01),
 	.quirks = DW_UART_QUIRK_CPR_VALUE | DW_UART_QUIRK_IS_DMA_FC,
 };
 

-- 
2.34.1

Re: [PATCH v4 2/4] serial: 8250_dw: build Renesas RZN1 CPR value from DW_UART_CPR_* definitions

[Ilpo Järvinen]

On Fri, 24 Apr 2026, Jia Wang wrote:

> Replace the magic CPR value for Renesas RZ/N1 with a composition using
> DW_UART_CPR_* bit/field definitions and FIELD_PREP_CONST().
> 
> Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
> ---
>  drivers/tty/serial/8250/8250_dw.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> index 467755bf0092..d3c2c9c84d9f 100644
> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -937,7 +937,15 @@ static const struct dw8250_platform_data dw8250_armada_38x_data = {
>  
>  static const struct dw8250_platform_data dw8250_renesas_rzn1_data = {
>  	.usr_reg = DW_UART_USR,
> -	.cpr_value = 0x00012f32,
> +	.cpr_value = FIELD_PREP_CONST(DW_UART_CPR_ABP_DATA_WIDTH, 2) |
> +		     DW_UART_CPR_AFCE_MODE |
> +		     DW_UART_CPR_THRE_MODE |
> +		     DW_UART_CPR_ADDITIONAL_FEATURES |
> +		     DW_UART_CPR_FIFO_ACCESS |
> +		     DW_UART_CPR_FIFO_STAT |
> +		     DW_UART_CPR_SHADOW |
> +		     DW_UART_CPR_DMA_EXTRA |
> +		     FIELD_PREP_CONST(DW_UART_CPR_FIFO_MODE, 0x01),

Hmm, maybe there should also be macro also for this one which takes the 
fifosize as input and converts it to CPR field vlaue (effectively, the 
macro is an inverse of DW_UART_CPR_FIFO_SIZE()). It would be more readable 
than the literal.

Also include BUILD_BUG_ON(!IS_ALIGNED(fifosize, 16) + bounds checks) 
inside that macro to catch invalid fifo sizes (+ don't forget the 
necessary headers for those two new things).


-- 
 i.

Re: [PATCH v4 2/4] serial: 8250_dw: build Renesas RZN1 CPR value from DW_UART_CPR_* definitions

[Andy Shevchenko]

On Fri, Apr 24, 2026 at 02:38:56PM +0300, Ilpo Järvinen wrote:
> On Fri, 24 Apr 2026, Jia Wang wrote:

...

> Hmm, maybe there should also be macro also for this one which takes the 
> fifosize as input and converts it to CPR field vlaue (effectively, the 
> macro is an inverse of DW_UART_CPR_FIFO_SIZE()). It would be more readable 
> than the literal.

But this can be done separately, right?

> Also include BUILD_BUG_ON(!IS_ALIGNED(fifosize, 16) + bounds checks) 
> inside that macro to catch invalid fifo sizes (+ don't forget the 
> necessary headers for those two new things).

Hmm... Some devices may have FIFO = 8 or 4 bytes (Intel Quark IIRC has less
than 16 and it's DW IP).

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 2/4] serial: 8250_dw: build Renesas RZN1 CPR value from DW_UART_CPR_* definitions

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 1154 bytes --]

On Fri, 24 Apr 2026, Andy Shevchenko wrote:

> On Fri, Apr 24, 2026 at 02:38:56PM +0300, Ilpo Järvinen wrote:
> > On Fri, 24 Apr 2026, Jia Wang wrote:
> 
> ...
> 
> > Hmm, maybe there should also be macro also for this one which takes the 
> > fifosize as input and converts it to CPR field vlaue (effectively, the 
> > macro is an inverse of DW_UART_CPR_FIFO_SIZE()). It would be more readable 
> > than the literal.
> 
> But this can be done separately, right?

It's logically part of the cpr_value literal to defines conversion (of 
course one could introduce it in own patch without users but I don't see 
much benefit from that).

> > Also include BUILD_BUG_ON(!IS_ALIGNED(fifosize, 16) + bounds checks) 
> > inside that macro to catch invalid fifo sizes (+ don't forget the 
> > necessary headers for those two new things).
> 
> Hmm... Some devices may have FIFO = 8 or 4 bytes (Intel Quark IIRC has less
> than 16 and it's DW IP).

Perhaps but according the DW databook I've at hand, there are no values in 
FIFO_MODE field for such FIFO sizes. So what would CPR contain in those
cases for FIFO_MODE field?

-- 
 i.

Re: [PATCH v4 2/4] serial: 8250_dw: build Renesas RZN1 CPR value from DW_UART_CPR_* definitions

[Andy Shevchenko]

On Fri, Apr 24, 2026 at 05:09:46PM +0300, Ilpo Järvinen wrote:
> On Fri, 24 Apr 2026, Andy Shevchenko wrote:
> > On Fri, Apr 24, 2026 at 02:38:56PM +0300, Ilpo Järvinen wrote:
> > > On Fri, 24 Apr 2026, Jia Wang wrote:

...

> > > Hmm, maybe there should also be macro also for this one which takes the 
> > > fifosize as input and converts it to CPR field vlaue (effectively, the 
> > > macro is an inverse of DW_UART_CPR_FIFO_SIZE()). It would be more readable 
> > > than the literal.
> > 
> > But this can be done separately, right?
> 
> It's logically part of the cpr_value literal to defines conversion (of 
> course one could introduce it in own patch without users but I don't see 
> much benefit from that).

No objections.

> > > Also include BUILD_BUG_ON(!IS_ALIGNED(fifosize, 16) + bounds checks) 
> > > inside that macro to catch invalid fifo sizes (+ don't forget the 
> > > necessary headers for those two new things).
> > 
> > Hmm... Some devices may have FIFO = 8 or 4 bytes (Intel Quark IIRC has less
> > than 16 and it's DW IP).
> 
> Perhaps but according the DW databook I've at hand, there are no values in 
> FIFO_MODE field for such FIFO sizes. So what would CPR contain in those
> cases for FIFO_MODE field?

On real HW it returns 0s for all registers above 0x07 (multiplied by 4 as
a stride). But I also checked the values of xmit_fifo_size and it shows 16.
What 8 is it is the DMA max_burst. Hence the proposed assertion should work.

-- 
With Best Regards,
Andy Shevchenko

[PATCH v4 3/4] dt-bindings: serial: snps-dw-apb-uart: Add UltraRISC DP1000 UART

[Jia Wang]

UltraRISC DP1000 integrates a Synopsys DesignWare APB UART, but it does
not provide the standard CPR and UCV registers.

Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
---
 Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
index 6efe43089a74..f84600f66df8 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
@@ -77,6 +77,7 @@ properties:
               - starfive,jh7100-hsuart
               - starfive,jh7100-uart
               - starfive,jh7110-uart
+              - ultrarisc,dp1000-uart
           - const: snps,dw-apb-uart
       - const: snps,dw-apb-uart
 

-- 
2.34.1

[PATCH v4 4/4] serial: 8250_dw: Use a fixed CPR value for UltraRISC DP1000 UART

[Jia Wang]

The UltraRISC DP1000 UART does not provide the standard CPR register used
by 8250_dw to discover port capabilities.

Provide a fixed CPR value for the DP1000-specific compatible so the
driver can configure the port correctly.

Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
---
 drivers/tty/serial/8250/8250_dw.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index d3c2c9c84d9f..43e60b0fb9fd 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -959,6 +959,15 @@ static const struct dw8250_platform_data dw8250_intc10ee = {
 	.quirks = DW_UART_QUIRK_IER_KICK,
 };
 
+static const struct dw8250_platform_data dw8250_ultrarisc_dp1000_data = {
+	.usr_reg = DW_UART_USR,
+	.cpr_value = FIELD_PREP_CONST(DW_UART_CPR_ABP_DATA_WIDTH, 2) |
+		     DW_UART_CPR_THRE_MODE |
+		     DW_UART_CPR_DMA_EXTRA |
+		     FIELD_PREP_CONST(DW_UART_CPR_FIFO_MODE, 0x02),
+	.quirks = DW_UART_QUIRK_CPR_VALUE,
+};
+
 static const struct of_device_id dw8250_of_match[] = {
 	{ .compatible = "snps,dw-apb-uart", .data = &dw8250_dw_apb },
 	{ .compatible = "cavium,octeon-3860-uart", .data = &dw8250_octeon_3860_data },
@@ -966,6 +975,7 @@ static const struct of_device_id dw8250_of_match[] = {
 	{ .compatible = "renesas,rzn1-uart", .data = &dw8250_renesas_rzn1_data },
 	{ .compatible = "sophgo,sg2044-uart", .data = &dw8250_skip_set_rate_data },
 	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_skip_set_rate_data },
+	{ .compatible = "ultrarisc,dp1000-uart", .data = &dw8250_ultrarisc_dp1000_data },
 	{ /* Sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, dw8250_of_match);

-- 
2.34.1

Re: [PATCH v4 0/4] serial: 8250_dw: Add support for UltraRISC DP1000 UART

[Andy Shevchenko]

On Fri, Apr 24, 2026 at 01:39:27PM +0800, Jia Wang wrote:
> This patch series adds support for the UltraRISC DP1000 UART controller.
> 
> The series includes four patches. The first two are preparatory cleanups;
> the last two add the DP1000 compatible and fixed CPR handling.
> 
> The patches have been tested on an UltraRISC DP1000 development board with
> Linux v7.0-rc7, verifying basic UART functionality.

Now it looks good to me, thanks!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
(except DT bindings, not an expert, no tag)

-- 
With Best Regards,
Andy Shevchenko