Re: [PATCH v5 09/44] drm: handle HAS_IOPORT dependencies

Thomas Zimmermann
2023-05-22T12:39:13Z

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Hi

Am 22.05.23 um 12:50 schrieb Niklas Schnelle:
> 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.
>
> 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.

I think we should consider making cirrus depend on HAS_IOPORT. The
driver is only for qemu's cirrus emulation, which IIRC can only be
enabled for i586. And it has all been deprecated long ago.

>
> Co-developed-by: Arnd Bergmann <arnd@kernel.org>
> Signed-off-by: Arnd Bergmann <arnd@kernel.org>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
> drivers/gpu/drm/qxl/Kconfig | 1 +
> drivers/gpu/drm/tiny/bochs.c | 17 +++++++++++++++++
> drivers/gpu/drm/tiny/cirrus.c | 2 ++
> 3 files changed, 20 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 d254679a136e..3710339407cc 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>

Why not <linux/bug.h> ?

>
> #include <drm/drm_aperture.h>
> #include <drm/drm_atomic_helper.h>
> @@ -105,7 +106,9 @@ static void bochs_vga_writeb(struct bochs_device *bochs, u16 ioport, u8 val)
>
> writeb(val, bochs->mmio + offset);
> } else {
> +#ifdef CONFIG_HAS_IOPORT
> outb(val, ioport);
> +#endif

Would it be feasible to define inb, inw, outb and outw at the top of
bochs.c if no HAS_IOPORT has been set? That would avoid the ifdef
branching within the code.

> }
> }
>
> @@ -119,7 +122,11 @@ static u8 bochs_vga_readb(struct bochs_device *bochs, u16 ioport)
>
> return readb(bochs->mmio + offset);
> } else {
> +#ifdef CONFIG_HAS_IOPORT
> return inb(ioport);
> +#else
> + return 0xff;
> +#endif
> }
> }
>
> @@ -132,8 +139,12 @@ static u16 bochs_dispi_read(struct bochs_device *bochs, u16 reg)
>
> ret = readw(bochs->mmio + offset);
> } else {
> +#ifdef CONFIG_HAS_IOPORT
> outw(reg, VBE_DISPI_IOPORT_INDEX);
> ret = inw(VBE_DISPI_IOPORT_DATA);
> +#else
> + ret = 0xffff;
> +#endif
> }
> return ret;
> }
> @@ -145,8 +156,10 @@ static void bochs_dispi_write(struct bochs_device *bochs, u16 reg, u16 val)
>
> writew(val, bochs->mmio + offset);
> } else {
> +#ifdef CONFIG_HAS_IOPORT
> outw(reg, VBE_DISPI_IOPORT_INDEX);
> outw(val, VBE_DISPI_IOPORT_DATA);
> +#endif
> }
> }
>
> @@ -229,6 +242,10 @@ static int bochs_hw_init(struct drm_device *dev)
> return -ENOMEM;
> }
> } else {
> + if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
> + DRM_ERROR("I/O ports are not supported\n");

Use drm_err() here.

Best regards
Thomas

> + return -EIO;
> + }
> ioaddr = VBE_DISPI_IOPORT_INDEX;
> iosize = 2;
> if (!request_region(ioaddr, iosize, "bochs-drm")) {
> diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
> index 594bc472862f..c65fea049bc7 100644
> --- a/drivers/gpu/drm/tiny/cirrus.c
> +++ b/drivers/gpu/drm/tiny/cirrus.c
> @@ -508,8 +508,10 @@ static void cirrus_crtc_helper_atomic_enable(struct drm_crtc *crtc,
>
> cirrus_mode_set(cirrus, &crtc_state->mode);
>
> +#ifdef CONFIG_HAS_IOPORT
> /* Unblank (needed on S3 resume, vgabios doesn't do it then) */
> outb(VGA_AR_ENABLE_DISPLAY, VGA_ATT_W);
> +#endif
>
> drm_dev_exit(idx);
> }

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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