On 03/10/2017 01:04 PM, Kishon Vijay Abraham I wrote: > Hi, > > On Thursday 09 March 2017 08:18 PM, Niklas Cassel wrote: >> On 03/09/2017 07:39 AM, Kishon Vijay Abraham I wrote: >>> Previously dbi accessors can be used to access data of size 4 >>> bytes. But there might be situations (like accessing >>> MSI_MESSAGE_CONTROL in order to set/get the number of required >>> MSI interrupts in EP mode) where dbi accessors must >>> be used to access data of size 2. This is in preparation for >>> adding endpoint mode support to designware driver. >> Hello Kishon >> >> I don't really like the idea of adding an extra argument to every existing read/write. >> Will not a read/write of length != 32 be quite uncommon compared to >> a read/write of length == 32? >> >> How about adding some defines to pcie-designware.h: >> >> #define dw_pcie_writel_dbi(pci, base, reg, val) dw_pcie_write_dbi(pci, base, reg, 0x4, val) >> #define dw_pcie_readl_dbi(pci, base, reg) dw_pcie_read_dbi(pci, base, reg, 0x4) >> >> That way we don't have to change every existing read/write. >> >> >> >> Is there a reason why we can't just do: >> >> vial = dw_pcie_readl_dbi(pci, base, MSI_MESSAGE_CONTROL); > MSI_MESSAGE_CONTROL is 0x52 (MSI capability offset + 2). I'm not sure if we can > do a readl that crosses the alignment boundary in all platforms. The other > option is to readl from "MSI capability offset + 0" and extract the last 16 > bits. I felt this is more clear since we are interested only in the > MSI_MESSAGE_CONTROL. > >> <shifting+masking the bits we need to get/set> >> dw_pcie_writel_dbi(pci, base, MSI_MESSAGE_CONTROL, val); >> >> Or are we going to be doing read/writes of length != 32 so often that >> you think that it's cleaner to have this abstraction? > it's used mainly for accessing configuration space header fields. Even the pci > core uses *pci_read_config_word* for accessing such fields. I see. Adding an extra size argument is a good thing then, since it's consistent with the pci generic code. However, I still think that having defines for writel/readl is a good thing :) > > Thanks > Kishon
