[PATCH 0/1] drm: Handle HAS_IOPORT dependencies

[PATCH 0/1] drm: Handle HAS_IOPORT dependencies

[Niklas Schnelle]

Hi DRM Maintainers,

This is a follow up in my ongoing effort of making inb()/outb() and
similar I/O port accessors compile-time optional. Previously I sent this
as a treewide series titled "treewide: Remove I/O port accessors for
HAS_IOPORT=n" with the latest being its 5th version[0]. With a significant
subset of patches merged I've changed over to per-subsystem series. These
series are stand alone and should be merged via the relevant tree such
that with all subsystems complete we can follow this up with the final
patch that will make the I/O port accessors compile-time optional.

The current state of the full series with changes to the remaining
subsystems and the aforementioned final patch can be found for your
convenience on my git.kernel.org tree in the has_ioport_v6 branch[1] with
signed tags. As for compile-time vs runtime see Linus' reply to my first
attempt[2].

Thanks,
Niklas

[0] https://lore.kernel.org/all/20230522105049.1467313-1-schnelle@linux.ibm.com/
[1] https://git.kernel.org/pub/scm/linux/kernel/git/niks/linux.git/log/?h=has_ioport_v6
[2] https://lore.kernel.org/lkml/CAHk-=wg80je=K7madF4e7WrRNp37e3qh6y10Svhdc7O8SZ_-8g@mail.gmail.com/

Niklas Schnelle (1):
  drm: handle HAS_IOPORT dependencies

 drivers/gpu/drm/qxl/Kconfig   |  1 +
 drivers/gpu/drm/tiny/bochs.c  | 17 +++++++++++++++++
 drivers/gpu/drm/tiny/cirrus.c |  2 ++
 drivers/gpu/drm/xe/Kconfig    |  2 +-
 4 files changed, 21 insertions(+), 1 deletion(-)

-- 
2.40.1

[PATCH 1/1] drm: handle HAS_IOPORT dependencies

[Niklas Schnelle]

In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
compile time. 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.

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>
---
Note: This patch does not depend any not-yet-mainline HAS_IOPORT changes
and may be merged via subsystem specific trees at your earliest
convenience.

v5->v6: Added HAS_IOPORT for xe driver which copied some I/O port use from
existing intel drivers.

 drivers/gpu/drm/qxl/Kconfig   |  1 +
 drivers/gpu/drm/tiny/bochs.c  | 17 +++++++++++++++++
 drivers/gpu/drm/tiny/cirrus.c |  2 ++
 drivers/gpu/drm/xe/Kconfig    |  2 +-
 4 files changed, 21 insertions(+), 1 deletion(-)

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 c23c9f0cf49c..9ac3b455ddce 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 +106,9 @@ 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
 	}
 }
 
@@ -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");
+			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 4e3a152f897a..716e1480c30f 100644
--- a/drivers/gpu/drm/tiny/cirrus.c
+++ b/drivers/gpu/drm/tiny/cirrus.c
@@ -509,8 +509,10 @@ 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);
 }
diff --git a/drivers/gpu/drm/xe/Kconfig b/drivers/gpu/drm/xe/Kconfig
index 1a556d087e63..519906b8e3de 100644
--- a/drivers/gpu/drm/xe/Kconfig
+++ b/drivers/gpu/drm/xe/Kconfig
@@ -48,7 +48,7 @@ config DRM_XE
 
 config DRM_XE_DISPLAY
 	bool "Enable display support"
-	depends on DRM_XE && DRM_XE=m
+	depends on DRM_XE && DRM_XE=m && HAS_IOPORT
 	select FB_IOMEM_HELPERS
 	select I2C
 	select I2C_ALGOBIT
-- 
2.40.1