Re: [PATCH v2 4/6] staging: vc04_services: vchiq_arm: Drop g_cache_line_size

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

Quoting Umang Jain (2024-03-14 10:06:05)
> The cache-line-size is cached in struct vchiq_drvdata.
> There is no need to cache this again via g_cache_line_size
> and use it. Instead use the value from vchiq_drvdata directly.
> 
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> ---
>  .../interface/vchiq_arm/vchiq_arm.c           | 50 +++++++++++--------
>  1 file changed, 30 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index 8c7520dee5f4..282f83b335d4 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -71,6 +71,16 @@ static struct vchiq_device *bcm2835_audio;
>  static struct vchiq_device *bcm2835_camera;
>  
>  static struct vchiq_drvdata bcm2835_drvdata = {
> +       /* This value is the size of the L2 cache lines as understood by the

This file has a mix of A)
 /* bulk multiline
  * comments like this
  */


and B)
 /*
  * Bulk multiline
  * comments like this
  */

I'd probably use B) when moving this, but again, no point for a respin
just for that. Only if there's another revision. Or a patch on top to
normalise throughout if you felt like it, as this is only a move anyway.

Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

> +        * VPU firmware, which determines the required alignment of the
> +        * offsets/sizes in pagelists.
> +        *
> +        * Modern VPU firmware looks for a DT "cache-line-size" property in
> +        * the VCHIQ node and will overwrite it with the actual L2 cache size,
> +        * which the kernel must then respect.  That property was rejected
> +        * upstream, so we have to use the VPU firmware's compatibility value
> +        * of 32.
> +        */
>         .cache_line_size = 32,
>  };
>  
> @@ -130,17 +140,6 @@ struct vchiq_pagelist_info {
>  };
>  
>  static void __iomem *g_regs;
> -/* This value is the size of the L2 cache lines as understood by the
> - * VPU firmware, which determines the required alignment of the
> - * offsets/sizes in pagelists.
> - *
> - * Modern VPU firmware looks for a DT "cache-line-size" property in
> - * the VCHIQ node and will overwrite it with the actual L2 cache size,
> - * which the kernel must then respect.  That property was rejected
> - * upstream, so we have to use the VPU firmware's compatibility value
> - * of 32.
> - */
> -static unsigned int g_cache_line_size = 32;
>  static unsigned int g_fragments_size;
>  static char *g_fragments_base;
>  static char *g_free_fragments;
> @@ -211,6 +210,8 @@ static struct vchiq_pagelist_info *
>  create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
>                 size_t count, unsigned short type)
>  {
> +       struct platform_device *pdev;
> +       struct vchiq_drvdata *drvdata;
>         struct pagelist *pagelist;
>         struct vchiq_pagelist_info *pagelistinfo;
>         struct page **pages;
> @@ -225,6 +226,9 @@ create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
>         if (count >= INT_MAX - PAGE_SIZE)
>                 return NULL;
>  
> +       pdev = to_platform_device(instance->state->dev->parent);
> +       drvdata = platform_get_drvdata(pdev);
> +
>         if (buf)
>                 offset = (uintptr_t)buf & (PAGE_SIZE - 1);
>         else
> @@ -367,9 +371,9 @@ create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
>  
>         /* Partial cache lines (fragments) require special measures */
>         if ((type == PAGELIST_READ) &&
> -           ((pagelist->offset & (g_cache_line_size - 1)) ||
> +           ((pagelist->offset & (drvdata->cache_line_size - 1)) ||
>             ((pagelist->offset + pagelist->length) &
> -           (g_cache_line_size - 1)))) {
> +           (drvdata->cache_line_size - 1)))) {
>                 char *fragments;
>  
>                 if (down_interruptible(&g_free_fragments_sema)) {
> @@ -395,12 +399,19 @@ static void
>  free_pagelist(struct vchiq_instance *instance, struct vchiq_pagelist_info *pagelistinfo,
>               int actual)
>  {
> +       struct platform_device *pdev;
> +       struct vchiq_drvdata *drvdata;
>         struct pagelist *pagelist = pagelistinfo->pagelist;
>         struct page **pages = pagelistinfo->pages;
>         unsigned int num_pages = pagelistinfo->num_pages;
> +       unsigned int cache_line_size;
>  
>         dev_dbg(instance->state->dev, "arm: %pK, %d\n", pagelistinfo->pagelist, actual);
>  
> +       pdev = to_platform_device(instance->state->dev->parent);
> +       drvdata = platform_get_drvdata(pdev);
> +       cache_line_size = drvdata->cache_line_size;
> +
>         /*
>          * NOTE: dma_unmap_sg must be called before the
>          * cpu can touch any of the data/pages.
> @@ -416,10 +427,10 @@ free_pagelist(struct vchiq_instance *instance, struct vchiq_pagelist_info *pagel
>                         g_fragments_size;
>                 int head_bytes, tail_bytes;
>  
> -               head_bytes = (g_cache_line_size - pagelist->offset) &
> -                       (g_cache_line_size - 1);
> +               head_bytes = (cache_line_size - pagelist->offset) &
> +                       (cache_line_size - 1);
>                 tail_bytes = (pagelist->offset + actual) &
> -                       (g_cache_line_size - 1);
> +                       (cache_line_size - 1);
>  
>                 if ((actual >= 0) && (head_bytes != 0)) {
>                         if (head_bytes > actual)
> @@ -434,8 +445,8 @@ free_pagelist(struct vchiq_instance *instance, struct vchiq_pagelist_info *pagel
>                     (tail_bytes != 0))
>                         memcpy_to_page(pages[num_pages - 1],
>                                 (pagelist->offset + actual) &
> -                               (PAGE_SIZE - 1) & ~(g_cache_line_size - 1),
> -                               fragments + g_cache_line_size,
> +                               (PAGE_SIZE - 1) & ~(cache_line_size - 1),
> +                               fragments + cache_line_size,
>                                 tail_bytes);
>  
>                 down(&g_free_fragments_mutex);
> @@ -478,8 +489,7 @@ static int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state
>         if (err < 0)
>                 return err;
>  
> -       g_cache_line_size = drvdata->cache_line_size;
> -       g_fragments_size = 2 * g_cache_line_size;
> +       g_fragments_size = 2 * drvdata->cache_line_size;
>  
>         /* Allocate space for the channels in coherent memory */
>         slot_mem_size = PAGE_ALIGN(TOTAL_SLOTS * VCHIQ_SLOT_SIZE);
> -- 
> 2.43.0
>