Re: [PATCH v3 01/12] PCI: rockchip-ep: Fix address translation unit programming

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Mon, Oct 07, 2024 at 01:12:07PM +0900, Damien Le Moal wrote:
> The rockchip PCIe endpoint controller handles PCIe transfers addresses
> by masking the lower bits of the programmed PCI address and using the
> same number of lower bits masked from the CPU address space used for the
> mapping. For a PCI mapping of <size> bytes starting from <pci_addr>,
> the number of bits masked is the number of address bits changing in the
> address range [pci_addr..pci_addr + size - 1].
> 
> However, rockchip_pcie_prog_ep_ob_atu() calculates num_pass_bits only
> using the size of the mapping, resulting in an incorrect number of mask
> bits depending on the value of the PCI address to map.
> 
> Fix this by introducing the helper function
> rockchip_pcie_ep_ob_atu_num_bits() to correctly calculate the number of
> mask bits to use to program the address translation unit. The number of
> mask bits iscalculated depending on both the PCI address and size of the
> mapping, and clamped between 8 and 20 using the macros
> ROCKCHIP_PCIE_AT_MIN_NUM_BITS and ROCKCHIP_PCIE_AT_MAX_NUM_BITS.
> 

How did you end up with these clamping values? Are the values (at least MAX
applicable to all SoCs)?

Btw, it would be helpful if you referenced the TRM and the section that
describes the outbound mapping. I'm able to find the reference:

Rockchip RK3399 TRM V1.3 Part2, Section 17.5.5.1.1

- Mani

> Fixes: cf590b078391 ("PCI: rockchip: Add EP driver for Rockchip PCIe controller")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>  drivers/pci/controller/pcie-rockchip-ep.c | 15 +++++++++++----
>  drivers/pci/controller/pcie-rockchip.h    |  4 ++++
>  2 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
> index 136274533656..27a7febb74e0 100644
> --- a/drivers/pci/controller/pcie-rockchip-ep.c
> +++ b/drivers/pci/controller/pcie-rockchip-ep.c
> @@ -63,16 +63,23 @@ static void rockchip_pcie_clear_ep_ob_atu(struct rockchip_pcie *rockchip,
>  			    ROCKCHIP_PCIE_AT_OB_REGION_DESC1(region));
>  }
>  
> +static int rockchip_pcie_ep_ob_atu_num_bits(struct rockchip_pcie *rockchip,
> +					    u64 pci_addr, size_t size)
> +{
> +	int num_pass_bits = fls64(pci_addr ^ (pci_addr + size - 1));
> +
> +	return clamp(num_pass_bits, ROCKCHIP_PCIE_AT_MIN_NUM_BITS,
> +		     ROCKCHIP_PCIE_AT_MAX_NUM_BITS);
> +}
> +
>  static void rockchip_pcie_prog_ep_ob_atu(struct rockchip_pcie *rockchip, u8 fn,
>  					 u32 r, u64 cpu_addr, u64 pci_addr,
>  					 size_t size)
>  {
> -	int num_pass_bits = fls64(size - 1);
> +	int num_pass_bits =
> +		rockchip_pcie_ep_ob_atu_num_bits(rockchip, pci_addr, size);
>  	u32 addr0, addr1, desc0;
>  
> -	if (num_pass_bits < 8)
> -		num_pass_bits = 8;
> -
>  	addr0 = ((num_pass_bits - 1) & PCIE_CORE_OB_REGION_ADDR0_NUM_BITS) |
>  		(lower_32_bits(pci_addr) & PCIE_CORE_OB_REGION_ADDR0_LO_ADDR);
>  	addr1 = upper_32_bits(pci_addr);
> diff --git a/drivers/pci/controller/pcie-rockchip.h b/drivers/pci/controller/pcie-rockchip.h
> index 6111de35f84c..15ee949f2485 100644
> --- a/drivers/pci/controller/pcie-rockchip.h
> +++ b/drivers/pci/controller/pcie-rockchip.h
> @@ -245,6 +245,10 @@
>  	(PCIE_EP_PF_CONFIG_REGS_BASE + (((fn) << 12) & GENMASK(19, 12)))
>  #define ROCKCHIP_PCIE_EP_VIRT_FUNC_BASE(fn) \
>  	(PCIE_EP_PF_CONFIG_REGS_BASE + 0x10000 + (((fn) << 12) & GENMASK(19, 12)))
> +
> +#define ROCKCHIP_PCIE_AT_MIN_NUM_BITS  8
> +#define ROCKCHIP_PCIE_AT_MAX_NUM_BITS  20
> +
>  #define ROCKCHIP_PCIE_AT_IB_EP_FUNC_BAR_ADDR0(fn, bar) \
>  	(PCIE_CORE_AXI_CONF_BASE + 0x0828 + (fn) * 0x0040 + (bar) * 0x0008)
>  #define ROCKCHIP_PCIE_AT_IB_EP_FUNC_BAR_ADDR1(fn, bar) \
> -- 
> 2.46.2
> 

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