Subject: Re: [PATCH v4 8/8] linux/log2.h: Use roundup/dow_pow_two() on 64bit calculations

From: Bjorn Helgaas <[email-masked]>
Date: Thu, 5 Dec 2019 14:38:45 -0600

The subject contains a couple typos: it's missing "of" and it's
missing the "n" on "down".

On Tue, Dec 03, 2019 at 12:47:41PM +0100, Nicolas Saenz Julienne wrote:
> The function now is safe to use while expecting a 64bit value. Use it
> where relevant.

Please include the function names ("roundup_pow_of_two()",
"rounddown_pow_of_two()") in the changelog so it is self-contained and
doesn't depend on the subject.

> Signed-off-by: Nicolas Saenz Julienne <[email-masked]>

With the nits above and below addressed,

Acked-by: Bjorn Helgaas <[email-masked]>	# drivers/pci

> ---
>  drivers/acpi/arm64/iort.c                        | 2 +-
>  drivers/net/ethernet/mellanox/mlx4/en_clock.c    | 3 ++-
>  drivers/of/device.c                              | 3 ++-
>  drivers/pci/controller/cadence/pcie-cadence-ep.c | 3 ++-
>  drivers/pci/controller/cadence/pcie-cadence.c    | 3 ++-
>  drivers/pci/controller/pcie-brcmstb.c            | 3 ++-
>  drivers/pci/controller/pcie-rockchip-ep.c        | 5 +++--
>  kernel/dma/direct.c                              | 2 +-
>  8 files changed, 15 insertions(+), 9 deletions(-)

> --- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> @@ -10,6 +10,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/sizes.h>
> +#include <linux/log2.h>
>  
>  #include "pcie-cadence.h"
>  
> @@ -65,7 +66,7 @@ static int cdns_pcie_ep_set_bar(struct pci_epc *epc, u8 fn,
>  	 * roundup_pow_of_two() returns an unsigned long, which is not suited
>  	 * for 64bit values.
>  	 */

Please remove the comment above since it no longer applies.

> -	sz = 1ULL << fls64(sz - 1);
> +	sz = roundup_pow_of_two(sz);
>  	aperture = ilog2(sz) - 7; /* 128B -> 0, 256B -> 1, 512B -> 2, ... */
>  
>  	if ((flags & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_IO) {
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.c b/drivers/pci/controller/cadence/pcie-cadence.c
> index cd795f6fc1e2..b1689f725b41 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence.c
> @@ -4,6 +4,7 @@
>  // Author: Cyrille Pitchen <[email-masked]>
>  
>  #include <linux/kernel.h>
> +#include <linux/log2.h>
>  
>  #include "pcie-cadence.h"
>  
> @@ -15,7 +16,7 @@ void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 fn,
>  	 * roundup_pow_of_two() returns an unsigned long, which is not suited
>  	 * for 64bit values.
>  	 */

Same here.

> -	u64 sz = 1ULL << fls64(size - 1);
> +	u64 sz = roundup_pow_of_two(size);
>  	int nbits = ilog2(sz);
>  	u32 addr0, addr1, desc0, desc1;
>  
> --- a/drivers/pci/controller/pcie-rockchip-ep.c
> +++ b/drivers/pci/controller/pcie-rockchip-ep.c
> @@ -16,6 +16,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/pci-epf.h>
>  #include <linux/sizes.h>
> +#include <linux/log2.h>
>  
>  #include "pcie-rockchip.h"
>  
> @@ -70,7 +71,7 @@ static void rockchip_pcie_prog_ep_ob_atu(struct rockchip_pcie *rockchip, u8 fn,
>  					 u32 r, u32 type, u64 cpu_addr,
>  					 u64 pci_addr, size_t size)
>  {
> -	u64 sz = 1ULL << fls64(size - 1);
> +	u64 sz = roundup_pow_of_two(size);
>  	int num_pass_bits = ilog2(sz);
>  	u32 addr0, addr1, desc0, desc1;
>  	bool is_nor_msg = (type == AXI_WRAPPER_NOR_MSG);
> @@ -176,7 +177,7 @@ static int rockchip_pcie_ep_set_bar(struct pci_epc *epc, u8 fn,
>  	 * roundup_pow_of_two() returns an unsigned long, which is not suited
>  	 * for 64bit values.
>  	 */

And here.

> -	sz = 1ULL << fls64(sz - 1);
> +	sz = roundup_pow_of_two(sz);
>  	aperture = ilog2(sz) - 7; /* 128B -> 0, 256B -> 1, 512B -> 2, ... */
>  
>  	if ((flags & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_IO) {
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 6af7ae83c4ad..056886c4efec 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -53,7 +53,7 @@ u64 dma_direct_get_required_mask(struct device *dev)
>  {
>  	u64 max_dma = phys_to_dma_direct(dev, (max_pfn - 1) << PAGE_SHIFT);
>  
> -	return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
> +	return rounddown_pow_of_two(max_dma) * 2 - 1;

Personally I would probably make this one a separate patch since it's
qualitatively different than the others and it would avoid the slight
awkwardness of the non-greppable "roundup/down_pow_of_two()"
construction in the commit subject.

But it's fine either way.

>  }
>  
>  static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
> -- 
> 2.24.0
>