[U-Boot] [RFC] ns16550: Add support for AUX regs usage on some ARC SoCs
Synopsys Data Fusion subsystem (DFSS) is targeted to deeply built-in use-cases and so to save some silicon area decision was made to escape usage of any busses and use instead directly wired to CPU peripherals. And one of those is DW APB UART.
Later DFSS became a part of larger and more complicated SoCs with some other peripherals connected via common buses but default UART is still used via ARC core's auxulary registers which are not mapped to "normal" address space and we use very special instructions to access them, thus we cannot simply reuse whatever accessor we have in 16550 UART as of now.
Also we cannot just switch inb()/outb() to access ARC AUX regs always for DFSS because other peripherals have normal memory-mapped control registers and we need to use normal accessors for them.
Frankly I don't like a lot what I did here but otherwise if I create a special driver for this I'll need to reimplement ns16550_serial_ops.putc()/getc() which will be pure copy-paseted from ns16550.c because the only difference is only in ns16550_{read|write}b().
As mentioned above we cannot remap those auxiliary registers to normal memory address-space and thus we have to use very special accessors write_aux_reg()/read_aux_reg() that directly use special CPU intructions (namely LR/SR) for dealing with ARC AUX regs.
Also note here I just use a check for a particular SoC being selected (CONFIG_ARCH_DFSS will be introduced shortly) but that is done just for simplicity, otherwise it might be a slecial Kconfig option for NS16550 or anything else.
I'd like to know what people think about possible colutions here. And as always any comments are much appreciated!
Signed-off-by: Alexey Brodkin abrodkin@synopsys.com Cc: Simon Glass sjg@chromium.org Cc: Tom Rini trini@konsulko.com Cc: Stefan Roese sr@denx.de --- drivers/serial/ns16550.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c index 6f9ce689cfff..75f342f337f1 100644 --- a/drivers/serial/ns16550.c +++ b/drivers/serial/ns16550.c @@ -13,6 +13,9 @@ #include <watchdog.h> #include <linux/types.h> #include <asm/io.h> +#ifdef CONFIG_ARCH_DFSS +#include <asm/arcregs.h> +#endif
DECLARE_GLOBAL_DATA_PTR;
@@ -53,7 +56,9 @@ DECLARE_GLOBAL_DATA_PTR;
static inline void serial_out_shift(void *addr, int shift, int value) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS + write_aux_reg((int)addr, value); +#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) outb(value, (ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) out_le32(addr, value); @@ -70,7 +75,9 @@ static inline void serial_out_shift(void *addr, int shift, int value)
static inline int serial_in_shift(void *addr, int shift) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS + return read_aux_reg((int)addr); +#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) return inb((ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) return in_le32(addr);
On Wed, Feb 21, 2018 at 03:26:05PM +0300, Alexey Brodkin wrote:
Synopsys Data Fusion subsystem (DFSS) is targeted to deeply built-in use-cases and so to save some silicon area decision was made to escape usage of any busses and use instead directly wired to CPU peripherals. And one of those is DW APB UART.
Later DFSS became a part of larger and more complicated SoCs with some other peripherals connected via common buses but default UART is still used via ARC core's auxulary registers which are not mapped to "normal" address space and we use very special instructions to access them, thus we cannot simply reuse whatever accessor we have in 16550 UART as of now.
Also we cannot just switch inb()/outb() to access ARC AUX regs always for DFSS because other peripherals have normal memory-mapped control registers and we need to use normal accessors for them.
Frankly I don't like a lot what I did here but otherwise if I create a special driver for this I'll need to reimplement ns16550_serial_ops.putc()/getc() which will be pure copy-paseted from ns16550.c because the only difference is only in ns16550_{read|write}b().
As mentioned above we cannot remap those auxiliary registers to normal memory address-space and thus we have to use very special accessors write_aux_reg()/read_aux_reg() that directly use special CPU intructions (namely LR/SR) for dealing with ARC AUX regs.
Also note here I just use a check for a particular SoC being selected (CONFIG_ARCH_DFSS will be introduced shortly) but that is done just for simplicity, otherwise it might be a slecial Kconfig option for NS16550 or anything else.
I'd like to know what people think about possible colutions here. And as always any comments are much appreciated!
Signed-off-by: Alexey Brodkin abrodkin@synopsys.com Cc: Simon Glass sjg@chromium.org Cc: Tom Rini trini@konsulko.com Cc: Stefan Roese sr@denx.de
drivers/serial/ns16550.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c index 6f9ce689cfff..75f342f337f1 100644 --- a/drivers/serial/ns16550.c +++ b/drivers/serial/ns16550.c @@ -13,6 +13,9 @@ #include <watchdog.h> #include <linux/types.h> #include <asm/io.h> +#ifdef CONFIG_ARCH_DFSS +#include <asm/arcregs.h> +#endif
DECLARE_GLOBAL_DATA_PTR;
@@ -53,7 +56,9 @@ DECLARE_GLOBAL_DATA_PTR;
static inline void serial_out_shift(void *addr, int shift, int value) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS
- write_aux_reg((int)addr, value);
+#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) outb(value, (ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) out_le32(addr, value); @@ -70,7 +75,9 @@ static inline void serial_out_shift(void *addr, int shift, int value)
static inline int serial_in_shift(void *addr, int shift) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS
- return read_aux_reg((int)addr);
+#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) return inb((ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) return in_le32(addr);
As always, thanks for the detailed explanation. Yes, I think that of the options, putting the details in read/write_aux_reg (and please make sure read/write_aux_reg have a good function comment too) is the best choice. Thanks!
Hi Tom,
On Thu, 2018-02-22 at 10:43 -0500, Tom Rini wrote:
On Wed, Feb 21, 2018 at 03:26:05PM +0300, Alexey Brodkin wrote:
[snip]
static inline void serial_out_shift(void *addr, int shift, int value) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS
- write_aux_reg((int)addr, value);
+#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) outb(value, (ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) out_le32(addr, value); @@ -70,7 +75,9 @@ static inline void serial_out_shift(void *addr, int shift, int value)
static inline int serial_in_shift(void *addr, int shift) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS
- return read_aux_reg((int)addr);
+#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) return inb((ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) return in_le32(addr);
As always, thanks for the detailed explanation. Yes, I think that of the options, putting the details in read/write_aux_reg (and please make sure read/write_aux_reg have a good function comment too) is the best choice. Thanks!
Frankly I didn't understand your comment well enough :) Do you suggest to keep proposed implementation (i.e. modification of serial_{in|out}_shift()) but add comments on what do we do and why or you really meant something completely different?
-Alexey
On Thu, Feb 22, 2018 at 04:07:39PM +0000, Alexey Brodkin wrote:
Hi Tom,
On Thu, 2018-02-22 at 10:43 -0500, Tom Rini wrote:
On Wed, Feb 21, 2018 at 03:26:05PM +0300, Alexey Brodkin wrote:
[snip]
static inline void serial_out_shift(void *addr, int shift, int value) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS
- write_aux_reg((int)addr, value);
+#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) outb(value, (ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) out_le32(addr, value); @@ -70,7 +75,9 @@ static inline void serial_out_shift(void *addr, int shift, int value)
static inline int serial_in_shift(void *addr, int shift) { -#ifdef CONFIG_SYS_NS16550_PORT_MAPPED +#ifdef CONFIG_ARCH_DFSS
- return read_aux_reg((int)addr);
+#elif defined(CONFIG_SYS_NS16550_PORT_MAPPED) return inb((ulong)addr); #elif defined(CONFIG_SYS_NS16550_MEM32) && !defined(CONFIG_SYS_BIG_ENDIAN) return in_le32(addr);
As always, thanks for the detailed explanation. Yes, I think that of the options, putting the details in read/write_aux_reg (and please make sure read/write_aux_reg have a good function comment too) is the best choice. Thanks!
Frankly I didn't understand your comment well enough :) Do you suggest to keep proposed implementation (i.e. modification of serial_{in|out}_shift()) but add comments on what do we do and why or you really meant something completely different?
I'm fine with what you have above, in the driver. I missed that read_aux_reg already exists, sorry. So I guess a detailed commit message will have to be enough documentation for future reviewers of the code. Or, we'll see what comes out of Simon's comments.
Hi,
On 21 February 2018 at 05:26, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Synopsys Data Fusion subsystem (DFSS) is targeted to deeply built-in use-cases and so to save some silicon area decision was made to escape usage of any busses and use instead directly wired to CPU peripherals. And one of those is DW APB UART.
Later DFSS became a part of larger and more complicated SoCs with some other peripherals connected via common buses but default UART is still used via ARC core's auxulary registers which are not mapped to "normal" address space and we use very special instructions to access them, thus we cannot simply reuse whatever accessor we have in 16550 UART as of now.
Also we cannot just switch inb()/outb() to access ARC AUX regs always for DFSS because other peripherals have normal memory-mapped control registers and we need to use normal accessors for them.
Frankly I don't like a lot what I did here but otherwise if I create a special driver for this I'll need to reimplement ns16550_serial_ops.putc()/getc() which will be pure copy-paseted from ns16550.c because the only difference is only in ns16550_{read|write}b().
As mentioned above we cannot remap those auxiliary registers to normal memory address-space and thus we have to use very special accessors write_aux_reg()/read_aux_reg() that directly use special CPU intructions (namely LR/SR) for dealing with ARC AUX regs.
Also note here I just use a check for a particular SoC being selected (CONFIG_ARCH_DFSS will be introduced shortly) but that is done just for simplicity, otherwise it might be a slecial Kconfig option for NS16550 or anything else.
I'd like to know what people think about possible colutions here. And as always any comments are much appreciated!
Signed-off-by: Alexey Brodkin abrodkin@synopsys.com Cc: Simon Glass sjg@chromium.org Cc: Tom Rini trini@konsulko.com Cc: Stefan Roese sr@denx.de
drivers/serial/ns16550.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
I think a separate driver might be better, unless we want to make the read/write interface go through regmap or similar?
Regards, Simon
Hi Simon,
On Thu, 2018-02-22 at 09:17 -0700, Simon Glass wrote:
Hi,
On 21 February 2018 at 05:26, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Synopsys Data Fusion subsystem (DFSS) is targeted to deeply built-in use-cases and so to save some silicon area decision was made to escape usage of any busses and use instead directly wired to CPU peripherals. And one of those is DW APB UART.
Later DFSS became a part of larger and more complicated SoCs with some other peripherals connected via common buses but default UART is still used via ARC core's auxulary registers which are not mapped to "normal" address space and we use very special instructions to access them, thus we cannot simply reuse whatever accessor we have in 16550 UART as of now.
Also we cannot just switch inb()/outb() to access ARC AUX regs always for DFSS because other peripherals have normal memory-mapped control registers and we need to use normal accessors for them.
Frankly I don't like a lot what I did here but otherwise if I create a special driver for this I'll need to reimplement ns16550_serial_ops.putc()/getc() which will be pure copy-paseted from ns16550.c because the only difference is only in ns16550_{read|write}b().
As mentioned above we cannot remap those auxiliary registers to normal memory address-space and thus we have to use very special accessors write_aux_reg()/read_aux_reg() that directly use special CPU intructions (namely LR/SR) for dealing with ARC AUX regs.
Also note here I just use a check for a particular SoC being selected (CONFIG_ARCH_DFSS will be introduced shortly) but that is done just for simplicity, otherwise it might be a slecial Kconfig option for NS16550 or anything else.
I'd like to know what people think about possible colutions here. And as always any comments are much appreciated!
Signed-off-by: Alexey Brodkin abrodkin@synopsys.com Cc: Simon Glass sjg@chromium.org Cc: Tom Rini trini@konsulko.com Cc: Stefan Roese sr@denx.de
drivers/serial/ns16550.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
I think a separate driver might be better, unless we want to make the read/write interface go through regmap or similar?
But in case of ARC's AUX regs portmap won't help because those AUX regs are couldn't be mapped - that a completely different address space and we may only access them via dedicated instructions (LR vs LD and SR vs ST).
-Alexey
Hi Alexey,
On 22 February 2018 at 09:23, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Hi Simon,
On Thu, 2018-02-22 at 09:17 -0700, Simon Glass wrote:
Hi,
On 21 February 2018 at 05:26, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Synopsys Data Fusion subsystem (DFSS) is targeted to deeply built-in use-cases and so to save some silicon area decision was made to escape usage of any busses and use instead directly wired to CPU peripherals. And one of those is DW APB UART.
Later DFSS became a part of larger and more complicated SoCs with some other peripherals connected via common buses but default UART is still used via ARC core's auxulary registers which are not mapped to "normal" address space and we use very special instructions to access them, thus we cannot simply reuse whatever accessor we have in 16550 UART as of now.
Also we cannot just switch inb()/outb() to access ARC AUX regs always for DFSS because other peripherals have normal memory-mapped control registers and we need to use normal accessors for them.
Frankly I don't like a lot what I did here but otherwise if I create a special driver for this I'll need to reimplement ns16550_serial_ops.putc()/getc() which will be pure copy-paseted from ns16550.c because the only difference is only in ns16550_{read|write}b().
As mentioned above we cannot remap those auxiliary registers to normal memory address-space and thus we have to use very special accessors write_aux_reg()/read_aux_reg() that directly use special CPU intructions (namely LR/SR) for dealing with ARC AUX regs.
Also note here I just use a check for a particular SoC being selected (CONFIG_ARCH_DFSS will be introduced shortly) but that is done just for simplicity, otherwise it might be a slecial Kconfig option for NS16550 or anything else.
I'd like to know what people think about possible colutions here. And as always any comments are much appreciated!
Signed-off-by: Alexey Brodkin abrodkin@synopsys.com Cc: Simon Glass sjg@chromium.org Cc: Tom Rini trini@konsulko.com Cc: Stefan Roese sr@denx.de
drivers/serial/ns16550.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
I think a separate driver might be better, unless we want to make the read/write interface go through regmap or similar?
But in case of ARC's AUX regs portmap won't help because those AUX regs are couldn't be mapped - that a completely different address space and we may only access them via dedicated instructions (LR vs LD and SR vs ST).
Well...
1. With a separate driver, you can do whatever you want :-) I know it introduces code duplication though...
2. With regmap you can add your own regmap driver, and again do whatever you want. I can help with that if it sounds attractive
Regards, Simon
Hi Simon,
On Thu, 2018-02-22 at 10:29 -0700, Simon Glass wrote:
Hi Alexey,
On 22 February 2018 at 09:23, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Hi Simon,
On Thu, 2018-02-22 at 09:17 -0700, Simon Glass wrote:
Hi,
On 21 February 2018 at 05:26, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
[snip]
drivers/serial/ns16550.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
I think a separate driver might be better, unless we want to make the read/write interface go through regmap or similar?
But in case of ARC's AUX regs portmap won't help because those AUX regs are couldn't be mapped - that a completely different address space and we may only access them via dedicated instructions (LR vs LD and SR vs ST).
Well...
- With a separate driver, you can do whatever you want :-) I know it
introduces code duplication though...
- With regmap you can add your own regmap driver, and again do
whatever you want. I can help with that if it sounds attractive
That sounds definitely interesting! Are there any pointers on how that usually done?
-Alexey
Hi Alexey,
On 23 February 2018 at 11:08, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Hi Simon,
On Thu, 2018-02-22 at 10:29 -0700, Simon Glass wrote:
Hi Alexey,
On 22 February 2018 at 09:23, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Hi Simon,
On Thu, 2018-02-22 at 09:17 -0700, Simon Glass wrote:
Hi,
On 21 February 2018 at 05:26, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
[snip]
drivers/serial/ns16550.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
I think a separate driver might be better, unless we want to make the read/write interface go through regmap or similar?
But in case of ARC's AUX regs portmap won't help because those AUX regs are couldn't be mapped - that a completely different address space and we may only access them via dedicated instructions (LR vs LD and SR vs ST).
Well...
- With a separate driver, you can do whatever you want :-) I know it
introduces code duplication though...
- With regmap you can add your own regmap driver, and again do
whatever you want. I can help with that if it sounds attractive
That sounds definitely interesting! Are there any pointers on how that usually done?
Not yet. My ideas:
- Add a new regmap_init_xxx() function - Adjust the regmap structure to allow read()/write() function pointers to be provided - Adjust the regmap code to call them, instead of the hard-coded memory-mapped ones - Adjust ns16550 to call regmap instead of readl/writel
This should clean up the mess in ns16550 a bit. But it will require a bit of investigation / thinking.
Regards, Simon
Hi Simon,
On Thu, 2018-02-22 at 10:29 -0700, Simon Glass wrote:
Hi Alexey,
On 22 February 2018 at 09:23, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Hi Simon,
On Thu, 2018-02-22 at 09:17 -0700, Simon Glass wrote:
[snip]
I think a separate driver might be better, unless we want to make the read/write interface go through regmap or similar?
But in case of ARC's AUX regs portmap won't help because those AUX regs are couldn't be mapped - that a completely different address space and we may only access them via dedicated instructions (LR vs LD and SR vs ST).
Well...
- With a separate driver, you can do whatever you want :-) I know it
introduces code duplication though...
Exactly I hate to introduce another driver which will be 99,9% the same as an existing one and then we'll need to care of it as well.
- With regmap you can add your own regmap driver, and again do
whatever you want. I can help with that if it sounds attractive
Ok so I took a look at regmap in Linux kernel and indeed that will solve our problem: we'll have a regmap-mmio.c and regmap-arcaux.c with appropriate implementation of accessors but I'm not really sure it worth the trouble. Or your idea was to move all the different #ifdefs from serial_{in|out}_shift() to the corresponding regmap implementations such that we have something like below: regmap-mem32-le.c regmap-mem32-be.c regmap-portmapped.c etc ?
Regards, Alexey
Hi Alexey.
On 2 March 2018 at 14:51, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Hi Simon,
On Thu, 2018-02-22 at 10:29 -0700, Simon Glass wrote:
Hi Alexey,
On 22 February 2018 at 09:23, Alexey Brodkin Alexey.Brodkin@synopsys.com wrote:
Hi Simon,
On Thu, 2018-02-22 at 09:17 -0700, Simon Glass wrote:
[snip]
I think a separate driver might be better, unless we want to make the read/write interface go through regmap or similar?
But in case of ARC's AUX regs portmap won't help because those AUX regs are couldn't be mapped - that a completely different address space and we may only access them via dedicated instructions (LR vs LD and SR vs ST).
Well...
- With a separate driver, you can do whatever you want :-) I know it
introduces code duplication though...
Exactly I hate to introduce another driver which will be 99,9% the same as an existing one and then we'll need to care of it as well.
- With regmap you can add your own regmap driver, and again do
whatever you want. I can help with that if it sounds attractive
Ok so I took a look at regmap in Linux kernel and indeed that will solve our problem: we'll have a regmap-mmio.c and regmap-arcaux.c with appropriate implementation of accessors but I'm not really sure it worth the trouble. Or your idea was to move all the different #ifdefs from serial_{in|out}_shift() to the corresponding regmap implementations such that we have something like below: regmap-mem32-le.c regmap-mem32-be.c regmap-portmapped.c etc ?
Yes, that's it.
I'm not sure why that driver is so special. Presumably other drivers would have the same problem?
Regards, Simon
participants (3)
-
Alexey Brodkin -
Simon Glass -
Tom Rini