[PATCH v2 4/7] drm/simpledrm: Add support for system memory framebuffers
Thomas Zimmermann
tzimmermann at suse.de
Mon Oct 10 08:12:34 UTC 2022
Hi
Am 07.10.22 um 14:49 schrieb Thierry Reding:
> From: Thierry Reding <treding at nvidia.com>
>
> Simple framebuffers can be set up in system memory, which cannot be
> requested and/or I/O remapped using the I/O resource helpers. Add a
> separate code path that obtains system memory framebuffers from the
> reserved memory region referenced in the memory-region property.
>
> v2: make screen base a struct iosys_map to avoid sparse warnings
Conversion to iosys_map has to be a separate patch.
>
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
> drivers/gpu/drm/tiny/simpledrm.c | 177 ++++++++++++++++++++++++-------
> 1 file changed, 141 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
> index 18489779fb8a..cf36f67d22e4 100644
> --- a/drivers/gpu/drm/tiny/simpledrm.c
> +++ b/drivers/gpu/drm/tiny/simpledrm.c
> @@ -2,6 +2,7 @@
>
> #include <linux/clk.h>
> #include <linux/of_clk.h>
> +#include <linux/of_reserved_mem.h>
> #include <linux/minmax.h>
> #include <linux/platform_data/simplefb.h>
> #include <linux/platform_device.h>
> @@ -207,7 +208,9 @@ struct simpledrm_device {
> unsigned int pitch;
>
> /* memory management */
> - void __iomem *screen_base;
> + struct iosys_map screen_base;
> + phys_addr_t sysmem_start;
> + size_t sysmem_size;
>
> /* modesetting */
> uint32_t formats[8];
> @@ -441,6 +444,106 @@ static int simpledrm_device_init_regulators(struct simpledrm_device *sdev)
> }
> #endif
>
> +/*
> + * Memory management
> + */
> +
> +static int simpledrm_device_init_mm_sysmem(struct simpledrm_device *sdev, phys_addr_t start,
> + size_t size)
> +{
> + struct drm_device *dev = &sdev->dev;
> + phys_addr_t end = start + size - 1;
> + void *screen_base;
> +
> + drm_info(dev, "using system memory framebuffer at [%pa-%pa]\n", &start, &end);
> +
> + screen_base = devm_memremap(dev->dev, start, size, MEMREMAP_WC);
> + if (!screen_base)
> + return -ENOMEM;
> +
> + iosys_map_set_vaddr(&sdev->screen_base, screen_base);
> +
> + return 0;
> +}
> +
> +static int simpledrm_device_init_mm_io(struct simpledrm_device *sdev, phys_addr_t start,
> + size_t size)
> +{
> + struct drm_device *dev = &sdev->dev;
> + phys_addr_t end = start + size - 1;
> + void __iomem *screen_base;
> + struct resource *mem;
> +
> + drm_info(dev, "using I/O memory framebuffer at [%pa-%pa]\n", &start, &end);
> +
> + mem = devm_request_mem_region(dev->dev, start, size, sdev->dev.driver->name);
> + if (!mem) {
> + /*
> + * We cannot make this fatal. Sometimes this comes from magic
> + * spaces our resource handlers simply don't know about. Use
> + * the I/O-memory resource as-is and try to map that instead.
> + */
> + drm_warn(dev, "could not acquire memory region [%pa-%pa]\n", &start, &end);
> + } else {
> + size = resource_size(mem);
> + start = mem->start;
> + }
> +
> + screen_base = devm_ioremap_wc(dev->dev, start, size);
> + if (!screen_base)
> + return -ENOMEM;
> +
> + iosys_map_set_vaddr_iomem(&sdev->screen_base, screen_base);
> +
> + return 0;
> +}
> +
> +static void simpledrm_device_exit_mm(void *data)
> +{
> + struct simpledrm_device *sdev = data;
> + struct drm_device *dev = &sdev->dev;
> +
> + of_reserved_mem_device_release(dev->dev);
> +}
> +
> +static int simpledrm_device_init_mm(struct simpledrm_device *sdev)
> +{
> + int (*init)(struct simpledrm_device *sdev, phys_addr_t start, size_t size);
> + struct drm_device *dev = &sdev->dev;
> + struct platform_device *pdev = to_platform_device(dev->dev);
> + phys_addr_t start, end;
> + size_t size;
> + int ret;
> +
> + ret = of_reserved_mem_device_init_by_idx(dev->dev, dev->dev->of_node, 0);
> + if (ret) {
> + struct resource *res;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -EINVAL;
> +
> + init = simpledrm_device_init_mm_io;
> + size = resource_size(res);
> + start = res->start;
> + } else {
> + devm_add_action_or_reset(dev->dev, simpledrm_device_exit_mm, sdev);
> + init = simpledrm_device_init_mm_sysmem;
> + start = sdev->sysmem_start;
> + size = sdev->sysmem_size;
> + }
> +
> + end = start + size - 1;
> +
> + ret = devm_aperture_acquire_from_firmware(dev, start, size);
> + if (ret) {
> + drm_err(dev, "could not acquire memory range [%pa-%pa]: %d\n", &start, &end, ret);
> + return ret;
> + }
> +
> + return init(sdev, start, size);
> +}
> +
That whole 'Memory Manangement' block is will be unmaintainable. Before
I go into a detailed review, please see my questions about the
reservedmem code at the end of the patch.
> /*
> * Modesetting
> */
> @@ -491,15 +594,15 @@ static void simpledrm_primary_plane_helper_atomic_update(struct drm_plane *plane
>
> drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
> drm_atomic_for_each_plane_damage(&iter, &damage) {
> - struct iosys_map dst = IOSYS_MAP_INIT_VADDR(sdev->screen_base);
> struct drm_rect dst_clip = plane_state->dst;
>
> if (!drm_rect_intersect(&dst_clip, &damage))
> continue;
>
> - iosys_map_incr(&dst, drm_fb_clip_offset(sdev->pitch, sdev->format, &dst_clip));
> - drm_fb_blit(&dst, &sdev->pitch, sdev->format->format, shadow_plane_state->data, fb,
> - &damage);
> + iosys_map_incr(&sdev->screen_base, drm_fb_clip_offset(sdev->pitch, sdev->format,
> + &dst_clip));
You'll modify screen_base and it'll eventually blow up. You have to keep
initializing the dst variable within the loop.
> + drm_fb_blit(&sdev->screen_base, &sdev->pitch, sdev->format->format,
> + shadow_plane_state->data, fb, &damage);
> }
>
> drm_dev_exit(idx);
> @@ -518,7 +621,7 @@ static void simpledrm_primary_plane_helper_atomic_disable(struct drm_plane *plan
> return;
>
> /* Clear screen to black if disabled */
> - memset_io(sdev->screen_base, 0, sdev->pitch * sdev->mode.vdisplay);
> + iosys_map_memset(&sdev->screen_base, 0, 0, sdev->pitch * sdev->mode.vdisplay);
>
> drm_dev_exit(idx);
> }
> @@ -635,8 +738,6 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
> struct drm_device *dev;
> int width, height, stride;
> const struct drm_format_info *format;
> - struct resource *res, *mem;
> - void __iomem *screen_base;
> struct drm_plane *primary_plane;
> struct drm_crtc *crtc;
> struct drm_encoder *encoder;
> @@ -706,35 +807,9 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
> drm_dbg(dev, "framebuffer format=%p4cc, size=%dx%d, stride=%d byte\n",
> &format->format, width, height, stride);
>
> - /*
> - * Memory management
> - */
> -
> - res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> - if (!res)
> - return ERR_PTR(-EINVAL);
> -
> - ret = devm_aperture_acquire_from_firmware(dev, res->start, resource_size(res));
> - if (ret) {
> - drm_err(dev, "could not acquire memory range %pr: error %d\n", res, ret);
> + ret = simpledrm_device_init_mm(sdev);
> + if (ret)
> return ERR_PTR(ret);
> - }
> -
> - mem = devm_request_mem_region(&pdev->dev, res->start, resource_size(res), drv->name);
> - if (!mem) {
> - /*
> - * We cannot make this fatal. Sometimes this comes from magic
> - * spaces our resource handlers simply don't know about. Use
> - * the I/O-memory resource as-is and try to map that instead.
> - */
> - drm_warn(dev, "could not acquire memory region %pr\n", res);
> - mem = res;
> - }
> -
> - screen_base = devm_ioremap_wc(&pdev->dev, mem->start, resource_size(mem));
> - if (!screen_base)
> - return ERR_PTR(-ENOMEM);
> - sdev->screen_base = screen_base;
>
> /*
> * Modesetting
> @@ -878,5 +953,35 @@ static struct platform_driver simpledrm_platform_driver = {
>
> module_platform_driver(simpledrm_platform_driver);
>
> +static int simple_framebuffer_device_init(struct reserved_mem *rmem, struct device *dev)
> +{
> + struct simpledrm_device *sdev = dev_get_drvdata(dev);
> +
> + sdev->sysmem_start = rmem->base;
> + sdev->sysmem_size = rmem->size;
From what I understand, you use the sysmem_ variables in the same code
that allocates the simpledrm_device, which creates a chicken-egg
problem. When does this code run?
> +
> + return 0;
> +}
> +
> +static void simple_framebuffer_device_release(struct reserved_mem *rmem, struct device *dev)
> +{
> +}
> +
> +static const struct reserved_mem_ops simple_framebuffer_ops = {
> + .device_init = simple_framebuffer_device_init,
> + .device_release = simple_framebuffer_device_release,
> +};
> +
> +static int simple_framebuffer_init(struct reserved_mem *rmem)
> +{
> + pr_info("framebuffer memory at %pa, size %lu bytes\n", &rmem->base,
> + (unsigned long)rmem->size);
> +
> + rmem->ops = &simple_framebuffer_ops;
> +
> + return 0;
> +}
> +RESERVEDMEM_OF_DECLARE(simple_framebuffer, "framebuffer", simple_framebuffer_init);
What's the prupose of these code at all? I looked through the kernel,
but there aren't many other examples of it.
Best regards
Thomas
> +
> MODULE_DESCRIPTION(DRIVER_DESC);
> MODULE_LICENSE("GPL v2");
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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