Re: [PATCH v3 03/12] PCI: rockchip-ep: Improve rockchip_pcie_ep_unmap_addr()

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

On 10/10/24 16:09, Manivannan Sadhasivam wrote:
> On Mon, Oct 07, 2024 at 01:12:09PM +0900, Damien Le Moal wrote:
>> From: Damien Le Moal <damien.lemoal@opensource.wdc.com>
>>
>> There is no need to loop over all regions to find the memory window used
>> to map an address. We can use rockchip_ob_region() to determine the
>> region index, together with a check that the address passed as argument
>> is the address used to create the mapping. Furthermore, the
>> ob_region_map bitmap should also be checked to ensure that we are not
>> attempting to unmap an address that is not mapped.
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
>> ---
>>  drivers/pci/controller/pcie-rockchip-ep.c | 8 ++------
>>  1 file changed, 2 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
>> index 5a07084fb7c4..89ebdf3e4737 100644
>> --- a/drivers/pci/controller/pcie-rockchip-ep.c
>> +++ b/drivers/pci/controller/pcie-rockchip-ep.c
>> @@ -256,13 +256,9 @@ static void rockchip_pcie_ep_unmap_addr(struct pci_epc *epc, u8 fn, u8 vfn,
>>  {
>>  	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
>>  	struct rockchip_pcie *rockchip = &ep->rockchip;
>> -	u32 r;
>> -
>> -	for (r = 0; r < ep->max_regions; r++)
>> -		if (ep->ob_addr[r] == addr)
>> -			break;
>> +	u32 r = rockchip_ob_region(addr);
>>  
>> -	if (r == ep->max_regions)
>> +	if (addr != ep->ob_addr[r] || !test_bit(r, &ep->ob_region_map))
> 
> Having these two checks looks redundant to me. Is it possible that an address
> could pass only one check?

Yes, if the wrong address is passed to rockchip_pcie_ep_unmap_addr() but that
address still correspond to an ob_region that is being used.

We could do add a WARN_ON_ONCE() around that if condition as calling that
function with an invalid address would mean that either the epc core or the
function driver is buggy.




-- 
Damien Le Moal
Western Digital Research