Re: [PATCH 2/3] firmware: qcom_scm: Cleanup code in qcom_scm_assign_mem()

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Fri 17 May 14:09 PDT 2019, Stephen Boyd wrote:

> There are some questionable coding styles in this function. It looks
> quite odd to deref a pointer with array indexing that only uses the
> first element. Also, destroying an input/output variable halfway through
> the function and then overwriting it on success is not clear. It's
> better to use a local variable and the kernel macros to step through
> each bit set in a bitmask and clearly show where outputs are set.
> 
> Cc: Ian Jackson <ian.jackson@citrix.com>
> Cc: Julien Grall <julien.grall@arm.com>
> Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
> Cc: Avaneesh Kumar Dwivedi <akdwived@codeaurora.org>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  drivers/firmware/qcom_scm.c | 34 ++++++++++++++++------------------
>  include/linux/qcom_scm.h    |  9 +++++----
>  2 files changed, 21 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 0c63495cf269..153f13f72bac 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -443,7 +443,8 @@ EXPORT_SYMBOL(qcom_scm_set_remote_state);
>   */
>  int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
>  			unsigned int *srcvm,
> -			struct qcom_scm_vmperm *newvm, int dest_cnt)
> +			const struct qcom_scm_vmperm *newvm,
> +			unsigned int dest_cnt)
>  {
>  	struct qcom_scm_current_perm_info *destvm;
>  	struct qcom_scm_mem_map_info *mem_to_map;
> @@ -458,11 +459,10 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
>  	int next_vm;
>  	__le32 *src;
>  	void *ptr;
> -	int ret;
> -	int len;
> -	int i;
> +	int ret, i, b;
> +	unsigned long srcvm_bits = *srcvm;
>  
> -	src_sz = hweight_long(*srcvm) * sizeof(*src);
> +	src_sz = hweight_long(srcvm_bits) * sizeof(*src);
>  	mem_to_map_sz = sizeof(*mem_to_map);
>  	dest_sz = dest_cnt * sizeof(*destvm);
>  	ptr_sz = ALIGN(src_sz, SZ_64) + ALIGN(mem_to_map_sz, SZ_64) +
> @@ -475,28 +475,26 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
>  
>  	/* Fill source vmid detail */
>  	src = ptr;
> -	len = hweight_long(*srcvm);
> -	for (i = 0; i < len; i++) {
> -		src[i] = cpu_to_le32(ffs(*srcvm) - 1);
> -		*srcvm ^= 1 << (ffs(*srcvm) - 1);
> -	}
> +	i = 0;
> +	for_each_set_bit(b, &srcvm_bits, sizeof(srcvm_bits))

The modem is sad that you only pass 8 here. Changed it to BITS_PER_LONG
to include the modem's permission bit and applied all three patches.

Thanks,
Bjorn

> +		src[i++] = cpu_to_le32(b);
>  
>  	/* Fill details of mem buff to map */
>  	mem_to_map = ptr + ALIGN(src_sz, SZ_64);
>  	mem_to_map_phys = ptr_phys + ALIGN(src_sz, SZ_64);
> -	mem_to_map[0].mem_addr = cpu_to_le64(mem_addr);
> -	mem_to_map[0].mem_size = cpu_to_le64(mem_sz);
> +	mem_to_map->mem_addr = cpu_to_le64(mem_addr);
> +	mem_to_map->mem_size = cpu_to_le64(mem_sz);
>  
>  	next_vm = 0;
>  	/* Fill details of next vmid detail */
>  	destvm = ptr + ALIGN(mem_to_map_sz, SZ_64) + ALIGN(src_sz, SZ_64);
>  	dest_phys = ptr_phys + ALIGN(mem_to_map_sz, SZ_64) + ALIGN(src_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);
> +	for (i = 0; i < dest_cnt; i++, destvm++, newvm++) {
> +		destvm->vmid = cpu_to_le32(newvm->vmid);
> +		destvm->perm = cpu_to_le32(newvm->perm);
> +		destvm->ctx = 0;
> +		destvm->ctx_size = 0;
> +		next_vm |= BIT(newvm->vmid);
>  	}
>  
>  	ret = __qcom_scm_assign_mem(__scm->dev, mem_to_map_phys, mem_to_map_sz,
> diff --git a/include/linux/qcom_scm.h b/include/linux/qcom_scm.h
> index d0aecc04c54b..1d406403c843 100644
> --- a/include/linux/qcom_scm.h
> +++ b/include/linux/qcom_scm.h
> @@ -57,8 +57,9 @@ extern int qcom_scm_pas_mem_setup(u32 peripheral, phys_addr_t addr,
>  extern int qcom_scm_pas_auth_and_reset(u32 peripheral);
>  extern int qcom_scm_pas_shutdown(u32 peripheral);
>  extern int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
> -			       unsigned int *src, struct qcom_scm_vmperm *newvm,
> -			       int dest_cnt);
> +			       unsigned int *src,
> +			       const struct qcom_scm_vmperm *newvm,
> +			       unsigned int dest_cnt);
>  extern void qcom_scm_cpu_power_down(u32 flags);
>  extern u32 qcom_scm_get_version(void);
>  extern int qcom_scm_set_remote_state(u32 state, u32 id);
> @@ -95,8 +96,8 @@ qcom_scm_pas_auth_and_reset(u32 peripheral) { return -ENODEV; }
>  static inline int qcom_scm_pas_shutdown(u32 peripheral) { return -ENODEV; }
>  static inline int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
>  				      unsigned int *src,
> -				      struct qcom_scm_vmperm *newvm,
> -				      int dest_cnt) { return -ENODEV; }
> +				      const struct qcom_scm_vmperm *newvm,
> +				      unsigned int dest_cnt) { return -ENODEV; }
>  static inline void qcom_scm_cpu_power_down(u32 flags) {}
>  static inline u32 qcom_scm_get_version(void) { return 0; }
>  static inline u32
> -- 
> Sent by a computer through tubes
>