Re: [PATCH v6 1/4] firmware: scm: Add new SCM call API for switching memory ownership

[Dwivedi, Avaneesh Kumar (avani)]

On 7/8/2017 4:19 AM, Stephen Boyd wrote:
> On 06/22, Avaneesh Kumar Dwivedi wrote:
> > diff --git a/drivers/firmware/qcom_scm-64.c b/drivers/firmware/qcom_scm-64.c
> > index 6e6d561..cdfe986 100644
> > --- a/drivers/firmware/qcom_scm-64.c
> > +++ b/drivers/firmware/qcom_scm-64.c
> > @@ -292,6 +304,86 @@ int qcom_scm_pas_shutdown(u32 peripheral)
> >   }
> >   EXPORT_SYMBOL(qcom_scm_pas_shutdown);
> >   
> > +/**
> > + * qcom_scm_assign_mem() - Make a secure call to reassign memory ownership
> > + *
> > + * @mem_addr: mem region whose ownership need to be reassigned
> > + * @mem_sz:   size of the region.
> > + * @srcvm:    vmid for current set of owners, each set bit in
> > + *            flag indicate a unique owner
> > + * @newvm:    array having new owners and corrsponding permission
> > + *            flags
> > + * @dest_cnt: number of owners in next set.
> > + * Return next set of owners on success.
> > + */
> > +int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz, int srcvm,
> > +			struct qcom_scm_vmperm *newvm, int dest_cnt)
> > +{
> > +	unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS;
> Why do we need this? Just curious if we can drop this.
The force contiguous flag is required with dma_alloc_attrs() api to 
allocate memory from physically contiguous zone.
I am not sure, are you saying that api will work without the attribute 
or you mean i shall use some api which does not take explicit attribute?
> > +	struct qcom_scm_current_perm_info *destvm;
> > +	struct qcom_scm_mem_map_info *mem;
> > +	phys_addr_t memory_phys;
> > +	phys_addr_t dest_phys;
> > +	phys_addr_t src_phys;
> > +	size_t mem_all_sz;
> > +	size_t memory_sz;
> > +	size_t dest_sz;
> > +	size_t src_sz;
> > +	int next_vm;
> > +	__le32 *src;
> > +	void *ptr;
> > +	int ret;
> > +	int len;
> > +	int i;
> > +
> > +	src_sz = hweight_long(srcvm) * sizeof(*src);
> > +	memory_sz = sizeof(*mem);
> > +	dest_sz = dest_cnt*sizeof(*destvm);
> > +	mem_all_sz = src_sz + memory_sz + dest_sz;
> > +
> > +	ptr = dma_alloc_attrs(__scm->dev, ALIGN(mem_all_sz, SZ_64),
> > +		&src_phys, GFP_KERNEL, dma_attrs);
> > +	if (!ptr)
> > +		return -ENOMEM;
> > +
> > +	/* Fill source vmid detail */
> > +	src = (__le32 *)ptr;
> Cast is necessary?
i removed many type casting but few still lingering, will check and 
remove whatever unnecessary.
> > +	len = hweight_long(srcvm);
> > +	for (i = 0; i < len; i++) {
> > +		src[i] = cpu_to_le32(ffs(srcvm) - 1);
> > +		srcvm ^= 1 << (ffs(srcvm) - 1);
> > +	}
> > +
> > +	/* Fill details of mem buff to map */
> > +	mem = ptr + ALIGN(src_sz, SZ_64);
> > +	memory_phys = src_phys + ALIGN(src_sz, SZ_64);
> > +	mem[0].mem_addr = cpu_to_le64(mem_addr);
> > +	mem[0].mem_size = cpu_to_le64(mem_sz);
> > +
> > +	next_vm = 0;
> > +	/* Fill details of next vmid detail */
> > +	destvm = ptr + ALIGN(memory_sz, SZ_64) + ALIGN(src_sz, SZ_64);
> > +	dest_phys = memory_phys + ALIGN(memory_sz, SZ_64);
> > +	for (i = 0; i < dest_cnt; i++) {
> > +		destvm[i].vmid = cpu_to_le32(newvm[i].vmid);
> > +		destvm[i].perm = cpu_to_le32(newvm[i].perm);
> > +		destvm[i].ctx = 0;
> > +		destvm[i].ctx_size = 0;
> > +		next_vm |= BIT(newvm[i].vmid);
> > +	}
> > +
> > +	ret = __qcom_scm_assign_mem(__scm->dev, memory_phys,
> > +		memory_sz, src_phys, src_sz, dest_phys, dest_sz);
> > +	dma_free_attrs(__scm->dev, ALIGN(mem_all_sz, SZ_64),
> > +		ptr, src_phys, dma_attrs);
> > +	if (ret == 0)
> > +		return next_vm;
> > +	else if (ret > 0)
> > +		return -ret;
> This still confuses me. Do we really just pass whatever the
> firmware tells us the error code is up to the caller? Shouldn't
> we be remapping the scm errors we receive to normal linux errnos?
because i do not know in advance what exactly will be the return error 
code, moreover there are number of error codes which are returned in 
case of failure
so if i have to return linux error code, i can not do one to one mapping 
of error code and will have to return single error code for all failure.
let me know your comments further on this.+ return ret;
> > +}
> > +EXPORT_SYMBOL(qcom_scm_assign_mem);
> > +
> >   static int qcom_scm_pas_reset_assert(struct reset_controller_dev *rcdev,
> >   				     unsigned long idx)
> >   {

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