linux-kernel - Re: [PATCH v3 2/2] serial: 8250: Apply FSL workarounds also without SERIAL_8250

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Date:   Mon, 5 Jun 2023 16:22:55 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Ellerman <mpe@...erman.id.au>, kernel@...gutronix.de,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kumaravel Thiagarajan <kumaravel.thiagarajan@...rochip.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Tharun Kumar P <tharunkumar.pasumarthi@...rochip.com>,
        Rob Herring <robh@...nel.org>, Helge Deller <deller@....de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Matthew Gerlach <matthew.gerlach@...ux.intel.com>,
        Liang He <windhl@....com>, linuxppc-dev@...ts.ozlabs.org,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] serial: 8250: Apply FSL workarounds also without
 SERIAL_8250_CONSOLE

On Mon, 5 Jun 2023, Uwe Kleine-König wrote:

> The need to handle the FSL variant of 8250 in a special way is also
> present without console support. So soften the dependency for
> SERIAL_8250_FSL accordingly. Note that with the 8250 driver compiled as
> a module, some devices still might not make use of the needed
> workarounds. That affects the ports instantiated in
> arch/powerpc/kernel/legacy_serial.c.
> 
> This issue was identified by Dominik Andreas Schorpp.
> 
> To cope for CONFIG_SERIAL_8250=m + CONFIG_SERIAL_8250_FSL=y, 8250_fsl.o
> must be put in the same compilation unit as 8250_port.o because the
> latter defines some functions needed in the former and so 8250_fsl.o
> must not be built-in if 8250_port.o is available in a module.
> 
> Acked-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Link: https://lore.kernel.org/r/20230531083230.2702181-1-u.kleine-koenig@pengutronix.de
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> ---
>  drivers/tty/serial/8250/Kconfig  | 2 +-
>  drivers/tty/serial/8250/Makefile | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
> index 5313aa31930f..10c09b19c871 100644
> --- a/drivers/tty/serial/8250/Kconfig
> +++ b/drivers/tty/serial/8250/Kconfig
> @@ -378,7 +378,7 @@ config SERIAL_8250_BCM2835AUX
>  
>  config SERIAL_8250_FSL
>  	bool "Freescale 16550 UART support" if COMPILE_TEST && !(PPC || ARM || ARM64)
> -	depends on SERIAL_8250_CONSOLE
> +	depends on SERIAL_8250

Just one additional thought: After the adding the arch side 
workaround/hack, SERIAL_8250_FSL could become a tristate?

(1/2 might need a small change to take into account that it can now be a 
module).

>  	default PPC || ARM || ARM64
>  	help
>  	  Selecting this option enables a workaround for a break-detection
> diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
> index 4fc2fc1f41b6..8824ba5295b6 100644
> --- a/drivers/tty/serial/8250/Makefile
> +++ b/drivers/tty/serial/8250/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_SERIAL_8250)		+= 8250.o 8250_base.o
>  8250_base-$(CONFIG_SERIAL_8250_DMA)	+= 8250_dma.o
>  8250_base-$(CONFIG_SERIAL_8250_DWLIB)	+= 8250_dwlib.o
>  8250_base-$(CONFIG_SERIAL_8250_FINTEK)	+= 8250_fintek.o
> +8250_base-$(CONFIG_SERIAL_8250_FSL)	+= 8250_fsl.o
>  8250_base-$(CONFIG_SERIAL_8250_PCILIB)	+= 8250_pcilib.o
>  obj-$(CONFIG_SERIAL_8250_PARISC)	+= 8250_parisc.o
>  obj-$(CONFIG_SERIAL_8250_PCI)		+= 8250_pci.o
> @@ -28,7 +29,6 @@ obj-$(CONFIG_SERIAL_8250_BOCA)		+= 8250_boca.o
>  obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554)	+= 8250_exar_st16c554.o
>  obj-$(CONFIG_SERIAL_8250_HUB6)		+= 8250_hub6.o
>  obj-$(CONFIG_SERIAL_8250_PCI1XXXX)	+= 8250_pci1xxxx.o
> -obj-$(CONFIG_SERIAL_8250_FSL)		+= 8250_fsl.o
>  obj-$(CONFIG_SERIAL_8250_MEN_MCB)	+= 8250_men_mcb.o
>  obj-$(CONFIG_SERIAL_8250_DFL)		+= 8250_dfl.o
>  obj-$(CONFIG_SERIAL_8250_DW)		+= 8250_dw.o

-- 
 i.