Re: [PATCH v4 06/11] staging: vc04_services: Move global variables tracking allocated pages

[Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>]

Hi Laurent,

On 29/03/24 4:34 am, Laurent Pinchart wrote:
> On Fri, Mar 29, 2024 at 12:59:59AM +0200, Laurent Pinchart wrote:
> > Hi Umang,
> >
> > Thank you for the patch.
> >
> > On Thu, Mar 28, 2024 at 11:41:28PM +0530, Umang Jain wrote:
> > > The variables tracking allocated pages fragments in vchiq_arm.c
> > > can be easily moved to struct vchiq_drv_mgmt instead of being global.
> > > This helps us to drop the non-essential global variables in the vchiq
> > > interface.
> > >
> > > No functional changes intended in this patch.
> > >
> > > Signed-off-by: Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> >
> > > ---
> > >   .../interface/vchiq_arm/vchiq_arm.c           | 53 +++++++++----------
> > >   .../interface/vchiq_arm/vchiq_arm.h           |  6 +++
> > >   2 files changed, 30 insertions(+), 29 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 2005d392d0b7..b335948f4b0c 100644
> > > --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> > > +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> > > @@ -130,12 +130,6 @@ struct vchiq_pagelist_info {
> > >   };
> > >   
> > >   static void __iomem *g_regs;
> > > -static unsigned int g_fragments_size;
> > > -static char *g_fragments_base;
> > > -static char *g_free_fragments;
> > > -static struct semaphore g_free_fragments_sema;
> > > -
> > > -static DEFINE_SEMAPHORE(g_free_fragments_mutex, 1);
> > >   
> > >   static int
> > >   vchiq_blocking_bulk_transfer(struct vchiq_instance *instance, unsigned int handle, void *data,
> > > @@ -414,20 +408,20 @@ create_pagelist(struct vchiq_instance *instance, char *buf, char __user *ubuf,
> > >   	    (drv_mgmt->info->cache_line_size - 1)))) {
> > >   		char *fragments;
> > >   
> > > -		if (down_interruptible(&g_free_fragments_sema)) {
> > > +		if (down_interruptible(&drv_mgmt->free_fragments_sema)) {
> > >   			cleanup_pagelistinfo(instance, pagelistinfo);
> > >   			return NULL;
> > >   		}
> > >   
> > > -		WARN_ON(!g_free_fragments);
> > > +		WARN_ON(!drv_mgmt->free_fragments);
> > >   
> > > -		down(&g_free_fragments_mutex);
> > > -		fragments = g_free_fragments;
> > > +		down(&drv_mgmt->free_fragments_mutex);
> > > +		fragments = drv_mgmt->free_fragments;
> > >   		WARN_ON(!fragments);
> > > -		g_free_fragments = *(char **)g_free_fragments;
> > > -		up(&g_free_fragments_mutex);
> > > +		drv_mgmt->free_fragments = *(char **)drv_mgmt->free_fragments;
> > > +		up(&drv_mgmt->free_fragments_mutex);
> > >   		pagelist->type = PAGELIST_READ_WITH_FRAGMENTS +
> > > -			(fragments - g_fragments_base) / g_fragments_size;
> > > +			(fragments - drv_mgmt->fragments_base) / drv_mgmt->fragments_size;
> > >   	}
> > >   
> > >   	return pagelistinfo;
> > > @@ -455,10 +449,10 @@ free_pagelist(struct vchiq_instance *instance, struct vchiq_pagelist_info *pagel
> > >   	pagelistinfo->scatterlist_mapped = 0;
> > >   
> > >   	/* Deal with any partial cache lines (fragments) */
> > > -	if (pagelist->type >= PAGELIST_READ_WITH_FRAGMENTS && g_fragments_base) {
> > > -		char *fragments = g_fragments_base +
> > > +	if (pagelist->type >= PAGELIST_READ_WITH_FRAGMENTS && drv_mgmt->fragments_base) {
> > > +		char *fragments = drv_mgmt->fragments_base +
> > >   			(pagelist->type - PAGELIST_READ_WITH_FRAGMENTS) *
> > > -			g_fragments_size;
> > > +			drv_mgmt->fragments_size;
> > >   		int head_bytes, tail_bytes;
> > >   
> > >   		head_bytes = (drv_mgmt->info->cache_line_size - pagelist->offset) &
> > > @@ -483,11 +477,11 @@ free_pagelist(struct vchiq_instance *instance, struct vchiq_pagelist_info *pagel
> > >   				fragments + drv_mgmt->info->cache_line_size,
> > >   				tail_bytes);
> > >   
> > > -		down(&g_free_fragments_mutex);
> > > -		*(char **)fragments = g_free_fragments;
> > > -		g_free_fragments = fragments;
> > > -		up(&g_free_fragments_mutex);
> > > -		up(&g_free_fragments_sema);
> > > +		down(&drv_mgmt->free_fragments_mutex);
> > > +		*(char **)fragments = drv_mgmt->free_fragments;
> > > +		drv_mgmt->free_fragments = fragments;
> > > +		up(&drv_mgmt->free_fragments_mutex);
> > > +		up(&drv_mgmt->free_fragments_sema);
> > >   	}
> > >   
> > >   	/* Need to mark all the pages dirty. */
> > > @@ -523,11 +517,11 @@ static int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state
> > >   	if (err < 0)
> > >   		return err;
> > >   
> > > -	g_fragments_size = 2 * drv_mgmt->info->cache_line_size;
> > > +	drv_mgmt->fragments_size = 2 * drv_mgmt->info->cache_line_size;
> > >   
> > >   	/* Allocate space for the channels in coherent memory */
> > >   	slot_mem_size = PAGE_ALIGN(TOTAL_SLOTS * VCHIQ_SLOT_SIZE);
> > > -	frag_mem_size = PAGE_ALIGN(g_fragments_size * MAX_FRAGMENTS);
> > > +	frag_mem_size = PAGE_ALIGN(drv_mgmt->fragments_size * MAX_FRAGMENTS);
> > >   
> > >   	slot_mem = dmam_alloc_coherent(dev, slot_mem_size + frag_mem_size,
> > >   				       &slot_phys, GFP_KERNEL);
> > > @@ -547,15 +541,16 @@ static int vchiq_platform_init(struct platform_device *pdev, struct vchiq_state
> > >   	vchiq_slot_zero->platform_data[VCHIQ_PLATFORM_FRAGMENTS_COUNT_IDX] =
> > >   		MAX_FRAGMENTS;
> > >   
> > > -	g_fragments_base = (char *)slot_mem + slot_mem_size;
> > > +	drv_mgmt->fragments_base = (char *)slot_mem + slot_mem_size;
> > >   
> > > -	g_free_fragments = g_fragments_base;
> > > +	drv_mgmt->free_fragments = drv_mgmt->fragments_base;
> > >   	for (i = 0; i < (MAX_FRAGMENTS - 1); i++) {
> > > -		*(char **)&g_fragments_base[i * g_fragments_size] =
> > > -			&g_fragments_base[(i + 1) * g_fragments_size];
> > > +		*(char **)&drv_mgmt->fragments_base[i * drv_mgmt->fragments_size] =
> > > +			&drv_mgmt->fragments_base[(i + 1) * drv_mgmt->fragments_size];
> > >   	}
> > > -	*(char **)&g_fragments_base[i * g_fragments_size] = NULL;
> > > -	sema_init(&g_free_fragments_sema, MAX_FRAGMENTS);
> > > +	*(char **)&drv_mgmt->fragments_base[i * drv_mgmt->fragments_size] = NULL;
> > > +	sema_init(&drv_mgmt->free_fragments_sema, MAX_FRAGMENTS);
> > > +	sema_init(&drv_mgmt->free_fragments_mutex, 1);
> > >   
> > >   	err = vchiq_init_state(state, vchiq_slot_zero, dev);
> > >   	if (err)
> > > diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
> > > index 4a5b5ae9625a..a3bba245bfe2 100644
> > > --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
> > > +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.h
> > > @@ -59,6 +59,12 @@ struct vchiq_drv_mgmt {
> > >   	struct mutex connected_mutex;
> > >   
> > >   	void (*deferred_callback[VCHIQ_DRV_MAX_CALLBACKS])(void);
> > > +
> > > +	struct semaphore free_fragments_sema;
> > > +	struct semaphore free_fragments_mutex;
> Could we turn the latter into a mutex (in a separate patch) ?

It can be on top. I have noted it down for next tranch of cleanups.
> > > +	char *fragments_base;
> > > +	char *free_fragments;
> > > +	unsigned int fragments_size;
> > >   };
> > >   
> > >   struct user_service {