<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body>  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. <a href="https://community.arm.com/support-forums/f/architectures-and-processors-forum/52046/how-to-read-write-an-i-o-port-in-aarch64" class="moz-txt-link-freetext">https://community.arm.com/support-forums/f/architectures-and-processors-forum/52046/how-to-read-write-an-i-o-port-in-aarch64</a> Thus, we want to adapt MMIO only after this patch. <div class="moz-cite-prefix">On 2023/4/17 下午 07:51, Thomas Zimmermann wrote: </div> <blockquote type="cite" cite="mid:24987cff-02e4-aa4a-449f-fd48accf7365@suse.de">Hi Am 07.04.23 um 04:09 schrieb Jammy Huang: <blockquote type="cite">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: <blockquote type="cite">ARM architecture only has 'memory', so all devices are accessed by MMIO. Signed-off-by: Jammy Huang <a class="moz-txt-link-rfc2396E" href="mailto:jammy_huang@aspeedtech.com"><jammy_huang@aspeedtech.com></a> --- 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); </blockquote> </blockquote> What happens on systems that use this branch? Best regards Thomas <blockquote type="cite"> <blockquote type="cite">- if (!ast->ioregs) - return ERR_PTR(-EIO); - } + ast->ioregs = ast->regs + AST_IO_MM_OFFSET; ast_detect_chip(dev, &need_post); base-commit: 254986e324add8a30d0019c6da59f81adc8b565f </blockquote> </blockquote> </blockquote> <pre class="moz-signature" cols="72">-- Best Regards Jammy</pre> </body> </html>