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Message-ID: <64bde1026a0af_7a6c729452@iweiny-mobl.notmuch>
Date: Sun, 23 Jul 2023 19:25:06 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Sumitra Sharma <sumitraartsy@...il.com>,
Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
David Airlie <airlied@...il.com>,
"Daniel Vetter" <daniel@...ll.ch>,
<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
Ira Weiny <ira.weiny@...el.com>,
Fabio <fmdefrancesco@...il.com>, Deepak R Varma <drv@...lo.com>,
Alison Schofield <alison.schofield@...el.com>
Subject: Re: [PATCH] Remove unnecessary calls to kmap{,_local_page}() when
acquiring pages using GFP_DMA32.
Sumitra Sharma wrote:
> The GFP_DMA32 uses the DMA32 zone to satisfy the allocation
> requests. Therefore, pages allocated with GFP_DMA32 cannot
> come from Highmem.
>
> Avoid using calls to kmap() / kunmap() as the kmap() is being
> deprecated [1].
>
> Avoid using calls to kmap_local_page() / kunmap_local() as the
> code does not depends on the implicit disable of migration of
> local mappings and is, in fact, an unnecessary overhead for
> the main code [2].
>
> Hence, use a plain page_address() directly in the
> psb_mmu_alloc_pd function.
>
> [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/
> [2]: https://lwn.net/Articles/836503/
>
> Suggested-by: Ira Weiny <ira.weiny@...el.com>
Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Sumitra Sharma <sumitraartsy@...il.com>
> ---
> drivers/gpu/drm/gma500/mmu.c | 11 +++--------
> 1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/gma500/mmu.c b/drivers/gpu/drm/gma500/mmu.c
> index a70b01ccdf70..1a44dd062fd1 100644
> --- a/drivers/gpu/drm/gma500/mmu.c
> +++ b/drivers/gpu/drm/gma500/mmu.c
> @@ -184,20 +184,15 @@ struct psb_mmu_pd *psb_mmu_alloc_pd(struct psb_mmu_driver *driver,
> pd->invalid_pte = 0;
> }
>
> - v = kmap_local_page(pd->dummy_pt);
> + v = page_address(pd->dummy_pt);
> for (i = 0; i < (PAGE_SIZE / sizeof(uint32_t)); ++i)
> v[i] = pd->invalid_pte;
>
> - kunmap_local(v);
> -
> - v = kmap_local_page(pd->p);
> + v = page_address(pd->p);
> for (i = 0; i < (PAGE_SIZE / sizeof(uint32_t)); ++i)
> v[i] = pd->invalid_pde;
>
> - kunmap_local(v);
> -
> - clear_page(kmap(pd->dummy_page));
> - kunmap(pd->dummy_page);
> + clear_page(page_address(pd->dummy_page));
>
> pd->tables = vmalloc_user(sizeof(struct psb_mmu_pt *) * 1024);
> if (!pd->tables)
> --
> 2.25.1
>
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