On Wed, 12 Sep 2018, Radu Pirea wrote: > On Wed, 2018-09-12 at 14:12 +0100, Lee Jones wrote: > > On Wed, 12 Sep 2018, Alexandre Belloni wrote: > > > > > On 12/09/2018 12:43:52+0100, Lee Jones wrote: > > > > > > But ... we can't have it both ways. *Either* it's a true > > > > > > MFD, in > > > > > > which case it can/should have 2 separate compatible strings > > > > > > which can > > > > > > be specified directly from the DT. *Or* it's not an MFD. In > > > > > > the > > > > > > latter case, which I think we're all agreeing on (else we'd > > > > > > have 2 > > > > > > compatible strings), MFD is not the place to handle this (my > > > > > > original > > > > > > point). > > > > > > > > > > > > > > > > If that is what bothers you, then let's move it out of mfd. > > > > > > > > As I've already mentioned. I don't just want it moved out of MFD > > > > and > > > > shoved somewhere else. My aim is to fix this properly. > > > > > > > > > > If it is out of MFD, then I'm not sure why you would care too much > > > about > > > it as you won't be maintaining that code. And I still this what was > > > done > > > was correct but I'm open to test what you suggest. > > > > I care for the kernel in general, not just the areas I'm responsible > > for. I guess I'm just that kinda guy! ;) > > Well, Lee, like you, I think this driver should not be a MFD driver, > but Alex has a good point of view. > > > > > > > > > So ... this is a USART device which can do SPI, right? > > > > > > > > > > > > My current thinking is that; as this is a USART device first > > > > > > & > > > > > > foremost, the USART should be probed in the first instance > > > > > > regardless, > > > > > > then if SPI mode is specified it (the USART driver) registers > > > > > > the SPI > > > > > > platform driver (as MFD does currently) and exits gracefully, > > > > > > allowing > > > > > > the SPI driver to take over. > > > > > > > > > > > > Spanner in the works: is it physically possible to change the > > > > > > mode at > > > > > > run-time? :s > > > > > > > > > > Yes it is possible but on Linux that will not happen without > > > > > probing > > > > > the drivers again. > > > > > > > > Not sure I understand what you mean. > > > > > > I was just commenting on changing the mode at runtime. > > > > Oh I see. My question was relating to whether the H/W is physically > > capable of changing modes on-the-fly, rather than how Linux would > > handle that. If this is something we'd wish to support, then it > > would > > have to be a single driver, which is why I was asking. By separating > > the drivers this way, we are blocking that as a > > possibility. Although > > I guess the OP has already thought about that and made the decision > > not to support it. > > Is possible to change modes on-the-fly, but you have no reason to do > that. On the PCB you will have a SPI slave or a serial console :) > Anyway, the current form of the driver, and through this I want to say > "this ugly hack", allows the user to switch from serial to SPI mode by > adding only one property to the device tree node of USART. If the > driver were in his first form, a simple SPI driver, how you will make a > dtsi file for an IP like this? You will add two nodes for the same IP > in dtsi and will take care to enable correct node in dts? > I think this driver is only a tradeoff between having an ugly hack in > kernel or having an messy device tree. > > > > > > > I'm suggesting that you use the same platform_* interfaces MFD > > > > uses to > > > > register the SPI driver if SPI mode has been selected. Only do > > > > so > > > > from the appropriate driver i.e. USART. > > > > > > Yeah, I understood that but I didn't comment because I'm not sure > > > this > > > will work yet. > > > > Other drivers already do this. > > Can you give me an example please? Sorry for the delay, I have been on vacation. Grep for 'platform_device_add' in drivers/ > I am open to suggestions. > > Sorry for that acked-by. There was a lot of "reviewed-by", "acked-by", > etc in a single version and I messed up :). > -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
