| Message ID | 1408096156-29772-2-git-send-email-bhupesh.sharma@freescale.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Aug 15, 2014 at 10:49:10AM +0100, Bhupesh Sharma wrote: > This patch addss the device-tree documentation for Freescale's > NS16550 UART (also called DUART). > > There is a specific errata fix required in FSL NS16550 UART > which ensures that an random interrupt storm is not observed when > a break is provided as an input to the UART. Should this not go in Documentation/devicetree/bindings/serial/of-serial.txt as with other NS16550A variations? The only code for handling this string seems to live in arch/powerpc/kernel/legacy_serial.c. Is there a patch factoring that out into common code? Or is the erratum not applicable to the revision used in your ARMv8 SoC? Thanks, Mark. > > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com> > --- > .../devicetree/bindings/serial/fsl-ns16550.txt | 24 ++++++++++++++++++++ > 1 file changed, 24 insertions(+) > create mode 100644 Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > diff --git a/Documentation/devicetree/bindings/serial/fsl-ns16550.txt b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > new file mode 100644 > index 0000000..9926e10 > --- /dev/null > +++ b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > @@ -0,0 +1,24 @@ > +* Freescale DUART is very similar to the PC16552D (and to a > + pair of NS16550A), albeit with some nonstandard behavior such as > + erratum A-004737 (relating to incorrect BRK handling). > + > +- compatible: "fsl,ns16550" > + > + Represents a single port that is compatible with the DUART found > + on many Freescale chips (examples include mpc8349, mpc8548, > + mpc8641d, p4080 and ls2085a). > + > +- reg: The base address of the UART register bank. > + > +- interrupts: A single interrupt specifier. > + > +- clock-frequency = Input clock to the baud rate divider. > + > +Example: > + serial1: serial@21c4600 { > + compatible = "fsl,ns16550", "ns16550a"; > + reg = <0x0 0x21c4600 0x0 0x100>; > + clock-frequency = <0>; > + interrupts = <0 32 0x1>; > + }; > + > -- > 1.7.9.5 > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
> -----Original Message----- > From: Mark Rutland [mailto:mark.rutland@arm.com] > Sent: Friday, August 15, 2014 4:16 PM > To: Sharma Bhupesh-B45370 > Cc: devicetree-discuss@lists.ozlabs.org; Catalin Marinas; arnd@arndb.de; > Will Deacon; Yoder Stuart-B08248; grant.likely@secretlab.ca; Basu Arnab- > B45036; linux-arm-kernel@lists.infradead.org > Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL NS16550A > UART > > On Fri, Aug 15, 2014 at 10:49:10AM +0100, Bhupesh Sharma wrote: > > This patch addss the device-tree documentation for Freescale's > > NS16550 UART (also called DUART). > > > > There is a specific errata fix required in FSL NS16550 UART which > > ensures that an random interrupt storm is not observed when a break is > > provided as an input to the UART. > > Should this not go in > Documentation/devicetree/bindings/serial/of-serial.txt as with other > NS16550A variations? > > The only code for handling this string seems to live in > arch/powerpc/kernel/legacy_serial.c. Is there a patch factoring that out > into common code? Or is the erratum not applicable to the revision used in > your ARMv8 SoC? > The FSL specific 8250 (or NS16550A0 driver) at path drivers/tty/serial/8250/8250_fsl.c uses this string and provides the code to handle the erratum (see [1]) The NS16550 UART present on our SoC and the corresponding simulator model has this erratum and hence the specific way in which IRQ are handled (fsl8250_handle_irq) by the driver (in [1]) is applicable here as well. [1] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/drivers/tty/serial/8250/8250_fsl.c?id=refs/tags/next-20140815 Regards, Bhupesh > Thanks, > Mark. > > > > > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com> > > --- > > .../devicetree/bindings/serial/fsl-ns16550.txt | 24 > ++++++++++++++++++++ > > 1 file changed, 24 insertions(+) > > create mode 100644 > > Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > > diff --git a/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > new file mode 100644 > > index 0000000..9926e10 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > @@ -0,0 +1,24 @@ > > +* Freescale DUART is very similar to the PC16552D (and to a > > + pair of NS16550A), albeit with some nonstandard behavior such as > > + erratum A-004737 (relating to incorrect BRK handling). > > + > > +- compatible: "fsl,ns16550" > > + > > + Represents a single port that is compatible with the DUART found > > + on many Freescale chips (examples include mpc8349, mpc8548, > > + mpc8641d, p4080 and ls2085a). > > + > > +- reg: The base address of the UART register bank. > > + > > +- interrupts: A single interrupt specifier. > > + > > +- clock-frequency = Input clock to the baud rate divider. > > + > > +Example: > > + serial1: serial@21c4600 { > > + compatible = "fsl,ns16550", "ns16550a"; > > + reg = <0x0 0x21c4600 0x0 0x100>; > > + clock-frequency = <0>; > > + interrupts = <0 32 0x1>; > > + }; > > + > > -- > > 1.7.9.5 > > > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > >
Hi Bhupesh, On Fri, Aug 15, 2014 at 03:42:09PM +0100, bhupesh.sharma@freescale.com wrote: > > -----Original Message----- > > From: Mark Rutland [mailto:mark.rutland@arm.com] > > Sent: Friday, August 15, 2014 4:16 PM > > To: Sharma Bhupesh-B45370 > > Cc: devicetree-discuss@lists.ozlabs.org; Catalin Marinas; arnd@arndb.de; > > Will Deacon; Yoder Stuart-B08248; grant.likely@secretlab.ca; Basu Arnab- > > B45036; linux-arm-kernel@lists.infradead.org > > Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL NS16550A > > UART > > > > On Fri, Aug 15, 2014 at 10:49:10AM +0100, Bhupesh Sharma wrote: > > > This patch addss the device-tree documentation for Freescale's > > > NS16550 UART (also called DUART). > > > > > > There is a specific errata fix required in FSL NS16550 UART which > > > ensures that an random interrupt storm is not observed when a break is > > > provided as an input to the UART. > > > > Should this not go in > > Documentation/devicetree/bindings/serial/of-serial.txt as with other > > NS16550A variations? > > > > The only code for handling this string seems to live in > > arch/powerpc/kernel/legacy_serial.c. Is there a patch factoring that out > > into common code? Or is the erratum not applicable to the revision used in > > your ARMv8 SoC? > > > > The FSL specific 8250 (or NS16550A0 driver) at path drivers/tty/serial/8250/8250_fsl.c > uses this string and provides the code to handle the erratum (see [1]) While the workaround itself is in that file, as far as I can see the detection and setup is not. Even in next-20140815 it seems that only happens in arch/powerpc/kernel/legacy_serial.c (see [2]): [mark@leverpostej:~/src/linux]% git grep fsl8250_handle_irq next-20140815 next-20140815:arch/powerpc/kernel/legacy_serial.c: port->handle_irq = fsl8250_handle_irq; next-20140815:drivers/tty/serial/8250/8250_fsl.c:int fsl8250_handle_irq(struct uart_port *port) next-20140815:include/linux/serial_8250.h:extern int fsl8250_handle_irq(struct uart_port *port); I cannot see any use of the string outside of arch/powerpc: [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 | wc -l 102 [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 -- arch/powerpc | wc -l 102 Am I missing something? Perhaps some macro is getting in the way of a simple grep. > The NS16550 UART present on our SoC and the corresponding simulator model has this erratum and > hence the specific way in which IRQ are handled (fsl8250_handle_irq) by the driver (in [1]) > is applicable here as well. Assuming I've not missed something, do you need to factor out the detection and setup? Do things just happen to work on the simulator without the workaround? Thanks, Mark. [2] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/arch/powerpc/kernel/legacy_serial.c?id=refs/tags/next-20140815#n478 > [1] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/drivers/tty/serial/8250/8250_fsl.c?id=refs/tags/next-20140815 > > Regards, > Bhupesh > > > Thanks, > > Mark. > > > > > > > > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com> > > > --- > > > .../devicetree/bindings/serial/fsl-ns16550.txt | 24 > > ++++++++++++++++++++ > > > 1 file changed, 24 insertions(+) > > > create mode 100644 > > > Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > > > > diff --git a/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > new file mode 100644 > > > index 0000000..9926e10 > > > --- /dev/null > > > +++ b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > @@ -0,0 +1,24 @@ > > > +* Freescale DUART is very similar to the PC16552D (and to a > > > + pair of NS16550A), albeit with some nonstandard behavior such as > > > + erratum A-004737 (relating to incorrect BRK handling). > > > + > > > +- compatible: "fsl,ns16550" > > > + > > > + Represents a single port that is compatible with the DUART found > > > + on many Freescale chips (examples include mpc8349, mpc8548, > > > + mpc8641d, p4080 and ls2085a). > > > + > > > +- reg: The base address of the UART register bank. > > > + > > > +- interrupts: A single interrupt specifier. > > > + > > > +- clock-frequency = Input clock to the baud rate divider. > > > + > > > +Example: > > > + serial1: serial@21c4600 { > > > + compatible = "fsl,ns16550", "ns16550a"; > > > + reg = <0x0 0x21c4600 0x0 0x100>; > > > + clock-frequency = <0>; > > > + interrupts = <0 32 0x1>; > > > + }; > > > + > > > -- > > > 1.7.9.5 > > > > > > > > > > > > _______________________________________________ > > > linux-arm-kernel mailing list > > > linux-arm-kernel@lists.infradead.org > > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > > >
Hi Mark, > -----Original Message----- > From: Mark Rutland [mailto:mark.rutland@arm.com] > Sent: Friday, August 15, 2014 8:34 PM > To: Sharma Bhupesh-B45370 > Cc: devicetree-discuss@lists.ozlabs.org; Catalin Marinas; arnd@arndb.de; > Will Deacon; Yoder Stuart-B08248; grant.likely@secretlab.ca; Basu Arnab- > B45036; linux-arm-kernel@lists.infradead.org > Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL NS16550A > The UART > > Hi Bhupesh, > > On Fri, Aug 15, 2014 at 03:42:09PM +0100, bhupesh.sharma@freescale.com > wrote: > > > -----Original Message----- > > > From: Mark Rutland [mailto:mark.rutland@arm.com] > > > Sent: Friday, August 15, 2014 4:16 PM > > > To: Sharma Bhupesh-B45370 > > > Cc: devicetree-discuss@lists.ozlabs.org; Catalin Marinas; > > > arnd@arndb.de; Will Deacon; Yoder Stuart-B08248; > > > grant.likely@secretlab.ca; Basu Arnab- B45036; > > > linux-arm-kernel@lists.infradead.org > > > Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL > > > NS16550A UART > > > > > > On Fri, Aug 15, 2014 at 10:49:10AM +0100, Bhupesh Sharma wrote: > > > > This patch addss the device-tree documentation for Freescale's > > > > NS16550 UART (also called DUART). > > > > > > > > There is a specific errata fix required in FSL NS16550 UART which > > > > ensures that an random interrupt storm is not observed when a > > > > break is provided as an input to the UART. > > > > > > Should this not go in > > > Documentation/devicetree/bindings/serial/of-serial.txt as with other > > > NS16550A variations? > > > > > > The only code for handling this string seems to live in > > > arch/powerpc/kernel/legacy_serial.c. Is there a patch factoring that > > > out into common code? Or is the erratum not applicable to the > > > revision used in your ARMv8 SoC? > > > > > > > The FSL specific 8250 (or NS16550A0 driver) at path > > drivers/tty/serial/8250/8250_fsl.c > > uses this string and provides the code to handle the erratum (see [1]) > > While the workaround itself is in that file, as far as I can see the > detection and setup is not. Even in next-20140815 it seems that only > happens in arch/powerpc/kernel/legacy_serial.c (see [2]): > > [mark@leverpostej:~/src/linux]% git grep fsl8250_handle_irq next-20140815 > next-20140815:arch/powerpc/kernel/legacy_serial.c: port- > >handle_irq = fsl8250_handle_irq; > next-20140815:drivers/tty/serial/8250/8250_fsl.c:int > fsl8250_handle_irq(struct uart_port *port) next- > 20140815:include/linux/serial_8250.h:extern int fsl8250_handle_irq(struct > uart_port *port); > > I cannot see any use of the string outside of arch/powerpc: > > [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 | wc -l > 102 > [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 -- > arch/powerpc | wc -l > 102 > > Am I missing something? Perhaps some macro is getting in the way of a > simple grep. > > > The NS16550 UART present on our SoC and the corresponding simulator > > model has this erratum and hence the specific way in which IRQ are > > handled (fsl8250_handle_irq) by the driver (in [1]) is applicable here > as well. > > Assuming I've not missed something, do you need to factor out the > detection and setup? Do things just happen to work on the simulator > without the workaround? You are right. The simulator platform doesn't take into account the erratum, however we need to take is into account for the emulator and silicon platforms. I am currently working to fork this out into a common code base so that both PPC and ARM platforms can use the same and a patch for the same is in my to-do list. So, I sent out the DT documentation patch early (as it is equally applicable to both PPC and ARM platforms) and the patch that makes this code leg usable for both ARM and PPC platform will follow soon. Regards, Bhupesh > Thanks, > Mark. > > [2] https://git.kernel.org/cgit/linux/kernel/git/next/linux- > next.git/tree/arch/powerpc/kernel/legacy_serial.c?id=refs/tags/next- > 20140815#n478 > > > [1] > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/ > > drivers/tty/serial/8250/8250_fsl.c?id=refs/tags/next-20140815 > > > > Regards, > > Bhupesh > > > > > Thanks, > > > Mark. > > > > > > > > > > > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com> > > > > --- > > > > .../devicetree/bindings/serial/fsl-ns16550.txt | 24 > > > ++++++++++++++++++++ > > > > 1 file changed, 24 insertions(+) > > > > create mode 100644 > > > > Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > > > > > > diff --git > > > > a/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > > b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > > new file mode 100644 > > > > index 0000000..9926e10 > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt > > > > @@ -0,0 +1,24 @@ > > > > +* Freescale DUART is very similar to the PC16552D (and to a > > > > + pair of NS16550A), albeit with some nonstandard behavior such > > > > +as > > > > + erratum A-004737 (relating to incorrect BRK handling). > > > > + > > > > +- compatible: "fsl,ns16550" > > > > + > > > > + Represents a single port that is compatible with the DUART > > > > + found on many Freescale chips (examples include mpc8349, > > > > + mpc8548, mpc8641d, p4080 and ls2085a). > > > > + > > > > +- reg: The base address of the UART register bank. > > > > + > > > > +- interrupts: A single interrupt specifier. > > > > + > > > > +- clock-frequency = Input clock to the baud rate divider. > > > > + > > > > +Example: > > > > + serial1: serial@21c4600 { > > > > + compatible = "fsl,ns16550", "ns16550a"; > > > > + reg = <0x0 0x21c4600 0x0 0x100>; > > > > + clock-frequency = <0>; > > > > + interrupts = <0 32 0x1>; > > > > + }; > > > > + > > > > -- > > > > 1.7.9.5 > > > > > > > > > > > > > > > > _______________________________________________ > > > > linux-arm-kernel mailing list > > > > linux-arm-kernel@lists.infradead.org > > > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > > > > >
Hi Bhupesh, [...] > > > > -----Original Message----- > > > > From: Mark Rutland [mailto:mark.rutland@arm.com] > > > > Sent: Friday, August 15, 2014 4:16 PM > > > > To: Sharma Bhupesh-B45370 > > > > Cc: devicetree-discuss@lists.ozlabs.org; Catalin Marinas; > > > > arnd@arndb.de; Will Deacon; Yoder Stuart-B08248; > > > > grant.likely@secretlab.ca; Basu Arnab- B45036; > > > > linux-arm-kernel@lists.infradead.org > > > > Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL > > > > NS16550A UART > > > > > > > > On Fri, Aug 15, 2014 at 10:49:10AM +0100, Bhupesh Sharma wrote: > > > > > This patch addss the device-tree documentation for Freescale's > > > > > NS16550 UART (also called DUART). > > > > > > > > > > There is a specific errata fix required in FSL NS16550 UART which > > > > > ensures that an random interrupt storm is not observed when a > > > > > break is provided as an input to the UART. > > > > > > > > Should this not go in > > > > Documentation/devicetree/bindings/serial/of-serial.txt as with other > > > > NS16550A variations? > > > > > > > > The only code for handling this string seems to live in > > > > arch/powerpc/kernel/legacy_serial.c. Is there a patch factoring that > > > > out into common code? Or is the erratum not applicable to the > > > > revision used in your ARMv8 SoC? > > > > > > > > > > The FSL specific 8250 (or NS16550A0 driver) at path > > > drivers/tty/serial/8250/8250_fsl.c > > > uses this string and provides the code to handle the erratum (see [1]) > > > > While the workaround itself is in that file, as far as I can see the > > detection and setup is not. Even in next-20140815 it seems that only > > happens in arch/powerpc/kernel/legacy_serial.c (see [2]): > > > > [mark@leverpostej:~/src/linux]% git grep fsl8250_handle_irq next-20140815 > > next-20140815:arch/powerpc/kernel/legacy_serial.c: port- > > >handle_irq = fsl8250_handle_irq; > > next-20140815:drivers/tty/serial/8250/8250_fsl.c:int > > fsl8250_handle_irq(struct uart_port *port) next- > > 20140815:include/linux/serial_8250.h:extern int fsl8250_handle_irq(struct > > uart_port *port); > > > > I cannot see any use of the string outside of arch/powerpc: > > > > [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 | wc -l > > 102 > > [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 -- > > arch/powerpc | wc -l > > 102 > > > > Am I missing something? Perhaps some macro is getting in the way of a > > simple grep. > > > > > The NS16550 UART present on our SoC and the corresponding simulator > > > model has this erratum and hence the specific way in which IRQ are > > > handled (fsl8250_handle_irq) by the driver (in [1]) is applicable here > > as well. > > > > Assuming I've not missed something, do you need to factor out the > > detection and setup? Do things just happen to work on the simulator > > without the workaround? > > You are right. The simulator platform doesn't take into account the > erratum, however we need to take is into account for the emulator and > silicon platforms. > > I am currently working to fork this out into a common code base so > that both PPC and ARM platforms can use the same and a patch for the > same is in my to-do list. > > So, I sent out the DT documentation patch early (as it is equally > applicable to both PPC and ARM platforms) and the patch that makes > this code leg usable for both ARM and PPC platform will follow soon. Ok. My only issue with the DT binding is the placement; I think that should live with the other NS16550A variations. Cheers, Mark.
Hi Mark, > -----Original Message----- > From: Mark Rutland [mailto:mark.rutland@arm.com] > Sent: Wednesday, August 20, 2014 5:02 PM > To: Sharma Bhupesh-B45370 > Cc: devicetree-discuss@lists.ozlabs.org; Catalin Marinas; arnd@arndb.de; > Will Deacon; Yoder Stuart-B08248; grant.likely@secretlab.ca; Basu Arnab- > B45036; linux-arm-kernel@lists.infradead.org > Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL NS16550A > The UART > > Hi Bhupesh, > > [...] > > > > > > -----Original Message----- > > > > > From: Mark Rutland [mailto:mark.rutland@arm.com] > > > > > Sent: Friday, August 15, 2014 4:16 PM > > > > > To: Sharma Bhupesh-B45370 > > > > > Cc: devicetree-discuss@lists.ozlabs.org; Catalin Marinas; > > > > > arnd@arndb.de; Will Deacon; Yoder Stuart-B08248; > > > > > grant.likely@secretlab.ca; Basu Arnab- B45036; > > > > > linux-arm-kernel@lists.infradead.org > > > > > Subject: Re: [PATCH 1/6] Documentation: DT: Add bindings for FSL > > > > > NS16550A UART > > > > > > > > > > On Fri, Aug 15, 2014 at 10:49:10AM +0100, Bhupesh Sharma wrote: > > > > > > This patch addss the device-tree documentation for Freescale's > > > > > > NS16550 UART (also called DUART). > > > > > > > > > > > > There is a specific errata fix required in FSL NS16550 UART > > > > > > which ensures that an random interrupt storm is not observed > > > > > > when a break is provided as an input to the UART. > > > > > > > > > > Should this not go in > > > > > Documentation/devicetree/bindings/serial/of-serial.txt as with > > > > > other NS16550A variations? > > > > > > > > > > The only code for handling this string seems to live in > > > > > arch/powerpc/kernel/legacy_serial.c. Is there a patch factoring > > > > > that out into common code? Or is the erratum not applicable to > > > > > the revision used in your ARMv8 SoC? > > > > > > > > > > > > > The FSL specific 8250 (or NS16550A0 driver) at path > > > > drivers/tty/serial/8250/8250_fsl.c > > > > uses this string and provides the code to handle the erratum (see > > > > [1]) > > > > > > While the workaround itself is in that file, as far as I can see the > > > detection and setup is not. Even in next-20140815 it seems that only > > > happens in arch/powerpc/kernel/legacy_serial.c (see [2]): > > > > > > [mark@leverpostej:~/src/linux]% git grep fsl8250_handle_irq next- > 20140815 > > > next-20140815:arch/powerpc/kernel/legacy_serial.c: port- > > > >handle_irq = fsl8250_handle_irq; > > > next-20140815:drivers/tty/serial/8250/8250_fsl.c:int > > > fsl8250_handle_irq(struct uart_port *port) next- > > > 20140815:include/linux/serial_8250.h:extern int > > > fsl8250_handle_irq(struct uart_port *port); > > > > > > I cannot see any use of the string outside of arch/powerpc: > > > > > > [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 | > > > wc -l > > > 102 > > > [mark@leverpostej:~/src/linux]% git grep fsl,ns16550 next-20140815 > > > -- arch/powerpc | wc -l > > > 102 > > > > > > Am I missing something? Perhaps some macro is getting in the way of > > > a simple grep. > > > > > > > The NS16550 UART present on our SoC and the corresponding > > > > simulator model has this erratum and hence the specific way in > > > > which IRQ are handled (fsl8250_handle_irq) by the driver (in [1]) > > > > is applicable here > > > as well. > > > > > > Assuming I've not missed something, do you need to factor out the > > > detection and setup? Do things just happen to work on the simulator > > > without the workaround? > > > > You are right. The simulator platform doesn't take into account the > > erratum, however we need to take is into account for the emulator and > > silicon platforms. > > > > I am currently working to fork this out into a common code base so > > that both PPC and ARM platforms can use the same and a patch for the > > same is in my to-do list. > > > > So, I sent out the DT documentation patch early (as it is equally > > applicable to both PPC and ARM platforms) and the patch that makes > > this code leg usable for both ARM and PPC platform will follow soon. > > Ok. > > My only issue with the DT binding is the placement; I think that should > live with the other NS16550A variations. Sure. I will look at how I can change the DT binding placement and then address it in my v2. Regards, Bhupesh > Cheers, > Mark.
diff --git a/Documentation/devicetree/bindings/serial/fsl-ns16550.txt b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt new file mode 100644 index 0000000..9926e10 --- /dev/null +++ b/Documentation/devicetree/bindings/serial/fsl-ns16550.txt @@ -0,0 +1,24 @@ +* Freescale DUART is very similar to the PC16552D (and to a + pair of NS16550A), albeit with some nonstandard behavior such as + erratum A-004737 (relating to incorrect BRK handling). + +- compatible: "fsl,ns16550" + + Represents a single port that is compatible with the DUART found + on many Freescale chips (examples include mpc8349, mpc8548, + mpc8641d, p4080 and ls2085a). + +- reg: The base address of the UART register bank. + +- interrupts: A single interrupt specifier. + +- clock-frequency = Input clock to the baud rate divider. + +Example: + serial1: serial@21c4600 { + compatible = "fsl,ns16550", "ns16550a"; + reg = <0x0 0x21c4600 0x0 0x100>; + clock-frequency = <0>; + interrupts = <0 32 0x1>; + }; +
This patch addss the device-tree documentation for Freescale's NS16550 UART (also called DUART). There is a specific errata fix required in FSL NS16550 UART which ensures that an random interrupt storm is not observed when a break is provided as an input to the UART. Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com> --- .../devicetree/bindings/serial/fsl-ns16550.txt | 24 ++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 Documentation/devicetree/bindings/serial/fsl-ns16550.txt