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

[Damien Le Moal <dlemoal@kernel.org>]

On 2024/10/10 16:02, Manivannan Sadhasivam wrote:
> 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

OK. Will add that.

I really appreciate very much all the reviews you are sending, but given that
this patch series depends on the series "[PATCH v4 0/7] Improve PCI memory
mapping API", could we start with that one and get it queued ASAP ?

Thanks !

-- 
Damien Le Moal
Western Digital Research