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Message-ID: <ZcDPn5eLvMwpb7N1@smile.fi.intel.com>
Date: Mon, 5 Feb 2024 14:08:00 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Howard Yen <howardyen@...gle.com>
Cc: hch@....de, m.szyprowski@...sung.com, robin.murphy@....com,
gregkh@...uxfoundation.org, rafael@...nel.org, broonie@...nel.org,
james@...iv.tech, james.clark@....com, masahiroy@...nel.org,
linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Subject: Re: [PATCH v2] dma-coherent: add support for multi coherent rmems
per dev
On Mon, Feb 05, 2024 at 07:23:00AM +0000, Howard Yen wrote:
> Add support for multiple coherent rmems per device. This patch replaces
> original dma_mem with dma_mems list in device structure to store multiple
> rmems.
>
> These multiple rmems can be assigned to the device one by one by
> of_reserved_mem_device_init_by_idx() with the memory-region
> declaration in device tree as below and store the rmem to the dma_mems
> list.
>
> device1@0 {
> ...
> memory-region = <&reserved_mem0>, <&reserved_mem1>;
> ...
> };
>
> When driver tries to allocate memory from the rmems, looks for the first
> available rmem and allocates the memory from this rmem.
>
> Then if driver removed, of_reserved_mem_device_release() needs to be
> invoked to release all the rmems assigned to the device.
..
> --- a/kernel/dma/coherent.c
> +++ b/kernel/dma/coherent.c
> @@ -18,15 +18,9 @@ struct dma_coherent_mem {
> unsigned long *bitmap;
> spinlock_t spinlock;
> bool use_dev_dma_pfn_offset;
> + struct list_head node;
Have you run `pahole`? Here I see wasted bytes for nothing.
> };
..
> void dma_release_coherent_memory(struct device *dev)
> {
> + struct dma_coherent_mem *mem_tmp, *q;
> +
> if (dev) {
While at it, perhaps
if (!dev)
return;
?
> - _dma_release_coherent_memory(dev->dma_mem);
> - dev->dma_mem = NULL;
> + list_for_each_entry_safe(mem_tmp, q, &dev->dma_mems, node) {
> + list_del_init(&mem_tmp->node);
> + _dma_release_coherent_memory(mem_tmp);
> + }
> }
> }
..
> int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr)
> {
> - struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
> + struct dma_coherent_mem *mem_tmp;
> + int ret = 0;
'ret' (1)
> - return __dma_release_from_coherent(mem, order, vaddr);
> + list_for_each_entry(mem_tmp, &dev->dma_mems, node) {
> + ret = __dma_release_from_coherent(mem_tmp, order, vaddr);
> + if (ret == 1)
> + break;
> + }
> +
> + return ret;
> }
..
> int dma_mmap_from_dev_coherent(struct device *dev, struct vm_area_struct *vma,
> void *vaddr, size_t size, int *ret)
> {
> - struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
> + struct dma_coherent_mem *mem_tmp;
> + int retval = 0;
'retval' (2)
Can we be consistent, please? (See (1) and (2) above.)
> + list_for_each_entry(mem_tmp, &dev->dma_mems, node) {
> + retval = __dma_mmap_from_coherent(mem_tmp, vma, vaddr, size, ret);
> + if (retval == 1)
> + break;
> + }
>
> - return __dma_mmap_from_coherent(mem, vma, vaddr, size, ret);
> + return retval;
> }
..
> static void rmem_dma_device_release(struct reserved_mem *rmem,
> struct device *dev)
> {
> - if (dev)
> - dev->dma_mem = NULL;
> + struct dma_coherent_mem *mem_tmp, *q;
> + if (dev) {
As per above, esp. taking into account that you touch this line. With proposed
modification you won't need to.
> + list_for_each_entry_safe(mem_tmp, q, &dev->dma_mems, node) {
> + if (mem_tmp == rmem->priv) {
> + list_del_init(&mem_tmp->node);
> + break;
> + }
> + }
> + }
> }
Better question, do we really need the dev check (at least in static functions)
or it can be ommitted?
--
With Best Regards,
Andy Shevchenko
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