linux-kernel - Re: [PATCH] staging: media: atomisp: Use kmap_local_page() in hmm

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Message-ID: <0b04ad1a-e442-1728-ef2c-bab386a4c64c@redhat.com>
Date:   Wed, 20 Apr 2022 13:07:05 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Tsuchiya Yuto <kitakar@...il.com>,
        Martiros Shakhzadyan <vrzh@...h.net>,
        linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>,
        outreachy@...ts.linux.dev
Subject: Re: [PATCH] staging: media: atomisp: Use kmap_local_page() in
 hmm_set()

Hi,

On 4/13/22 23:22, Fabio M. De Francesco wrote:
> The use of kmap() is being deprecated in favor of kmap_local_page()
> where it is feasible. In file pci/hmm/hmm.c, function hmm_set() calls
> kmap() / kunmap() where kmap_local_page() can instead do the mapping.
> 
> With kmap_local_page(), the mapping is per thread, CPU local and not
> globally visible. Therefore, hmm_set()() is a function where the use
> of kmap_local_page() in place of kmap() is correctly suited.
> 
> Convert the calls of kmap() / kunmap() to kmap_local_page() /
> kunmap_local().
> 
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>


I've successfully tested this on both the front and back cams
of a chuwi hi8 tablet:

Tested-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans



> ---
>  drivers/staging/media/atomisp/pci/hmm/hmm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/pci/hmm/hmm.c b/drivers/staging/media/atomisp/pci/hmm/hmm.c
> index 6394385b6637..46ac082cd3f1 100644
> --- a/drivers/staging/media/atomisp/pci/hmm/hmm.c
> +++ b/drivers/staging/media/atomisp/pci/hmm/hmm.c
> @@ -563,7 +563,7 @@ int hmm_set(ia_css_ptr virt, int c, unsigned int bytes)
>  		idx = (virt - bo->start) >> PAGE_SHIFT;
>  		offset = (virt - bo->start) - (idx << PAGE_SHIFT);
>  
> -		des = (char *)kmap(bo->page_obj[idx].page) + offset;
> +		des = (char *)kmap_local_page(bo->page_obj[idx].page) + offset;
>  
>  		if ((bytes + offset) >= PAGE_SIZE) {
>  			len = PAGE_SIZE - offset;
> @@ -579,7 +579,7 @@ int hmm_set(ia_css_ptr virt, int c, unsigned int bytes)
>  
>  		clflush_cache_range(des, len);
>  
> -		kunmap(bo->page_obj[idx].page);
> +		kunmap_local(des);
>  	}
>  
>  	return 0;