linux-kernel - Re: [PATCH v3 07/38] drm: handle HAS

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Date:   Wed, 15 Mar 2023 13:54:49 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Dave Airlie <airlied@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     linux-arch@...r.kernel.org, Arnd Bergmann <arnd@...nel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        virtualization@...ts.linux-foundation.org,
        Alan Stern <stern@...land.harvard.edu>,
        spice-devel@...ts.freedesktop.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>
Subject: Re: [PATCH v3 07/38] drm: handle HAS_IOPORT dependencies

On Tue, 14 Mar 2023, Niklas Schnelle <schnelle@...ux.ibm.com> wrote:
> In a future patch HAS_IOPORT=n will result in inb()/outb() and friends
> not being declared. We thus need to add HAS_IOPORT as dependency for
> those drivers using them. In the bochs driver there is optional MMIO
> support detected at runtime, warn if this isn't taken when
> HAS_IOPORT is not defined.

Not that I care a whole lot, but there should really only be one warning
or even failure to probe at bochs_hw_init() for !bochs->mmio &&
!IS_ENABLED(CONFIG_HAS_IOPORT), not warnings all over the place.

Moreover, the config macro is CONFIG_HAS_IOPORT instead of HAS_IOPORT
that you check for below.

BR,
Jani.

> There is also a direct and hard coded use in cirrus.c which according to
> the comment is only necessary during resume.  Let's just skip this as
> for example s390 which doesn't have I/O port support also doesen't
> support suspend/resume.
>
> Co-developed-by: Arnd Bergmann <arnd@...nel.org>
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> ---
>  drivers/gpu/drm/qxl/Kconfig   |  1 +
>  drivers/gpu/drm/tiny/bochs.c  | 19 +++++++++++++++++++
>  drivers/gpu/drm/tiny/cirrus.c |  2 ++
>  3 files changed, 22 insertions(+)
>
> diff --git a/drivers/gpu/drm/qxl/Kconfig b/drivers/gpu/drm/qxl/Kconfig
> index ca3f51c2a8fe..d0e0d440c8d9 100644
> --- a/drivers/gpu/drm/qxl/Kconfig
> +++ b/drivers/gpu/drm/qxl/Kconfig
> @@ -2,6 +2,7 @@
>  config DRM_QXL
>  	tristate "QXL virtual GPU"
>  	depends on DRM && PCI && MMU
> +	depends on HAS_IOPORT
>  	select DRM_KMS_HELPER
>  	select DRM_TTM
>  	select DRM_TTM_HELPER
> diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c
> index 024346054c70..da4a5d53b003 100644
> --- a/drivers/gpu/drm/tiny/bochs.c
> +++ b/drivers/gpu/drm/tiny/bochs.c
> @@ -2,6 +2,7 @@
>  
>  #include <linux/module.h>
>  #include <linux/pci.h>
> +#include <asm/bug.h>
>  
>  #include <drm/drm_aperture.h>
>  #include <drm/drm_atomic_helper.h>
> @@ -105,7 +106,11 @@ static void bochs_vga_writeb(struct bochs_device *bochs, u16 ioport, u8 val)
>  
>  		writeb(val, bochs->mmio + offset);
>  	} else {
> +#ifdef HAS_IOPORT
>  		outb(val, ioport);
> +#else
> +		WARN_ONCE(1, "Non-MMIO bochs device needs HAS_IOPORT");
> +#endif
>  	}
>  }
>  
> @@ -119,7 +124,12 @@ static u8 bochs_vga_readb(struct bochs_device *bochs, u16 ioport)
>  
>  		return readb(bochs->mmio + offset);
>  	} else {
> +#ifdef HAS_IOPORT
>  		return inb(ioport);
> +#else
> +		WARN_ONCE(1, "Non-MMIO bochs device needs HAS_IOPORT");
> +		return 0xff;
> +#endif
>  	}
>  }
>  
> @@ -132,8 +142,13 @@ static u16 bochs_dispi_read(struct bochs_device *bochs, u16 reg)
>  
>  		ret = readw(bochs->mmio + offset);
>  	} else {
> +#ifdef HAS_IOPORT
>  		outw(reg, VBE_DISPI_IOPORT_INDEX);
>  		ret = inw(VBE_DISPI_IOPORT_DATA);
> +#else
> +		WARN_ONCE(1, "Non-MMIO bochs device needs HAS_IOPORT");
> +		ret = 0xffff;
> +#endif
>  	}
>  	return ret;
>  }
> @@ -145,8 +160,12 @@ static void bochs_dispi_write(struct bochs_device *bochs, u16 reg, u16 val)
>  
>  		writew(val, bochs->mmio + offset);
>  	} else {
> +#ifdef HAS_IOPORT
>  		outw(reg, VBE_DISPI_IOPORT_INDEX);
>  		outw(val, VBE_DISPI_IOPORT_DATA);
> +#else
> +		WARN_ONCE(1, "Non-MMIO bochs device needs HAS_IOPORT");
> +#endif
>  	}
>  }
>  
> diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
> index accfa52e78c5..9da89732c5ac 100644
> --- a/drivers/gpu/drm/tiny/cirrus.c
> +++ b/drivers/gpu/drm/tiny/cirrus.c
> @@ -308,8 +308,10 @@ static int cirrus_mode_set(struct cirrus_device *cirrus,
>  
>  	cirrus_set_start_address(cirrus, 0);
>  
> +#ifdef CONFIG_HAS_IOPORT
>  	/* Unblank (needed on S3 resume, vgabios doesn't do it then) */
>  	outb(0x20, 0x3c0);
> +#endif
>  
>  	drm_dev_exit(idx);
>  	return 0;

-- 
Jani Nikula, Intel Open Source Graphics Center