Hi Thomas,
Thanks for you reminder. The comment you mentioned is added in 2014 for
AST2400 rev 0x20, which means MMIO is not enable by default before that
revision. I will send another patch to handle it.
On 2023/4/18 下午 03:24, Thomas Zimmermann wrote:
Hi
Am 18.04.23 um 03:23 schrieb Jammy Huang:
Hi Thomas,
The Intel(x86) CPUs have a separate address space for "IO", but the
ARM architecture only has "memory", so all IO devices are accessed as
if they were memory. Which means ARM does not support isolated IO.
Here is a related discussion on ARM's forum.
https://community.arm.com/support-forums/f/architectures-and-processors-forum/52046/how-to-read-write-an-i-o-port-in-aarch64
Thus, we want to adapt MMIO only after this patch.
What I mean is that there's a comment that says "assume the chip has
MMIO enabled by default (rev 0x20 and higher)". We also support revs
before 0x20. What happens to them?
Best regards
Thomas
On 2023/4/17 下午 07:51, Thomas Zimmermann wrote:
Hi
Am 07.04.23 um 04:09 schrieb Jammy Huang:
Hi Thomas,
Could you help review this patch??
We met some problem on nvidia's ARM platfrom and need this patch to
fix it.
On 2023/3/2 上午 10:19, Jammy Huang wrote:
ARM architecture only has 'memory', so all devices are accessed by
MMIO.
Signed-off-by: Jammy Huang <jammy_huang@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/ast/ast_main.c | 17 +----------------
1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/gpu/drm/ast/ast_main.c
b/drivers/gpu/drm/ast/ast_main.c
index 794ffd4a29c5..f86d01e9f024 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -424,22 +424,7 @@ struct ast_device *ast_device_create(const
struct drm_driver *drv,
if (!ast->regs)
return ERR_PTR(-EIO);
- /*
- * If we don't have IO space at all, use MMIO now and
- * assume the chip has MMIO enabled by default (rev 0x20
- * and higher).
- */
- if (!(pci_resource_flags(pdev, 2) & IORESOURCE_IO)) {
- drm_info(dev, "platform has no IO space, trying MMIO\n");
- ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
- }
-
- /* "map" IO regs if the above hasn't done so already */
- if (!ast->ioregs) {
- ast->ioregs = pcim_iomap(pdev, 2, 0);
What happens on systems that use this branch?
Best regards
Thomas
- if (!ast->ioregs)
- return ERR_PTR(-EIO);
- }
+ ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
ast_detect_chip(dev, &need_post);
base-commit: 254986e324add8a30d0019c6da59f81adc8b565f
--
Best Regards
Jammy
--
Best Regards
Jammy
