| Message ID | 20211127223253.19098-1-semen.protsenko@linaro.org |
|---|---|
| Headers | show |
| Series | soc: samsung: Add USIv2 driver | expand |
On Sun, 2021-11-28 at 00:32 +0200, Sam Protsenko wrote: > USIv2 IP-core provides selectable serial protocol (UART, SPI or > High-Speed I2C); only one can be chosen at a time. This series > implements USIv2 driver, which allows one to select particular USI > function in device tree, and also performs USI block initialization. > > With that driver implemented, it's not needed to do USI > initialization > in protocol drivers anymore, so that code is removed from the serial > driver. > I think the downstream way of doing this (USI node reg being on the SW_CONF register itself rather than an offset from uart/i2c/spi, the USI driver only controlling the SW_CONF, and the uart/i2c/spi drivers controlling their USI_CON and USI_OPTION regs) is cleaner, better, and easier to adapt to USIv1 too. For example: I'm sure this is the case on USIv2 devices too, but on Exynos7885, different devices have USI modes configured differently. For example a Samsung Galaxy A8 (2018) has all the USI blocks configured as SPI while a Samsung Galaxy M20 has the first USI configured as dual HSI2C, the second as HSI2C on the first 2 pins and the third as HSI2C on the last 2 pins. With this way of doing everything on USIv2 we'd need 3 disabled USIv2 nodes in the SoC DTSI for one USI block, each for every protocol the USI block can do, all having a single child for their protocol and each referencing the same sysreg (not even sure if that's even supported). Then the board DTS could enable the USI node it needs. With the downstream way we could have just one USI node and we could add the 3 protocols it can do disabled as seperate or child nodes. This way the board DTS only needs to set the appropriate mode setting and enable the protocol it needs. I'd say much better than having 3 USI nodes for the same USI block. Also this way is pretty USIv2 centric. Adding USIv1 support to this driver is difficult this way because of the the lack of USI_CON and USI_OPTION registers as a whole (so having nowhere to actually set the reg of the USI node to, as the only thing USIv1 has is the SW_CONF register). In my opinion being able to use the same driver and same device tree layout for USIv1 and USIv2 is a definite plus The only real drawback of that way is having to add code for USIv2 inside the UART, HSI2C, and SPI drivers but in my opinion the benefits overweigh the drawbacks greatly. We could even make the uart/spi/hsi2c drivers call a helper function in the USI driver to set their USI_CON and USI_OPTION registers up so that code would be shared and not duplicated. Wether this patch gets applied like this is not my choice though, I'll let the people responsible decide :-) Anyways, soon enough I can write an USIv1 driver after I submit all the 7885 stuff I'm working on currently. If you want to, you can add USIv2 support to that driver, or if an USIv2 driver is already in upstream at that point, if it is written in the downstream way I can add v1 support to that, or if it's like this I'll have to make a whole seperate driver with a whole seperate DT structure. Best regards, David
On 28/11/2021 04:15, David Virag wrote: > On Sun, 2021-11-28 at 00:32 +0200, Sam Protsenko wrote: >> USIv2 IP-core provides selectable serial protocol (UART, SPI or >> High-Speed I2C); only one can be chosen at a time. This series >> implements USIv2 driver, which allows one to select particular USI >> function in device tree, and also performs USI block initialization. >> >> With that driver implemented, it's not needed to do USI >> initialization >> in protocol drivers anymore, so that code is removed from the serial >> driver. >> > > I think the downstream way of doing this (USI node reg being on the > SW_CONF register itself rather than an offset from uart/i2c/spi, the > USI driver only controlling the SW_CONF, and the uart/i2c/spi drivers > controlling their USI_CON and USI_OPTION regs) is cleaner, better, and > easier to adapt to USIv1 too. > > For example: I'm sure this is the case on USIv2 devices too, but on > Exynos7885, different devices have USI modes configured differently. > For example a Samsung Galaxy A8 (2018) has all the USI blocks > configured as SPI while a Samsung Galaxy M20 has the first USI > configured as dual HSI2C, the second as HSI2C on the first 2 pins and > the third as HSI2C on the last 2 pins. With this way of doing > everything on USIv2 we'd need 3 disabled USIv2 nodes in the SoC DTSI > for one USI block, each for every protocol the USI block can do, all > having a single child for their protocol and each referencing the same > sysreg (not even sure if that's even supported). Then the board DTS > could enable the USI node it needs. It's not supported (one cannot have three same nodes with same unit addresses), so this would be solved by dropping out unused interfaces, commenting them out or storing everything under one USI: usi@0x1abcdef0 { serial@.... { status = "okay"; } i2c@.... { status = "disabled"; } spi@.... { status = "disabled"; } } > > With the downstream way we could have just one USI node and we could > add the 3 protocols it can do disabled as seperate or child nodes. This > way the board DTS only needs to set the appropriate mode setting and > enable the protocol it needs. I'd say much better than having 3 USI > nodes for the same USI block. Then however you need to handle probe ordering and possible probe deferrals. > > Also this way is pretty USIv2 centric. Adding USIv1 support to this > driver is difficult this way because of the the lack of USI_CON and > USI_OPTION registers as a whole (so having nowhere to actually set the > reg of the USI node to, as the only thing USIv1 has is the SW_CONF > register). How is it difficult? Not having a register is easy - noop on given platform. > In my opinion being able to use the same driver and same > device tree layout for USIv1 and USIv2 is a definite plus > > The only real drawback of that way is having to add code for USIv2 > inside the UART, HSI2C, and SPI drivers but in my opinion the benefits > overweigh the drawbacks greatly. We could even make the uart/spi/hsi2c > drivers call a helper function in the USI driver to set their USI_CON > and USI_OPTION registers up so that code would be shared and not > duplicated. Wether this patch gets applied like this is not my choice > though, I'll let the people responsible decide > :-) > > Anyways, soon enough I can write an USIv1 driver after I submit all the > 7885 stuff I'm working on currently. If you want to, you can add USIv2 > support to that driver, or if an USIv2 driver is already in upstream at > that point, if it is written in the downstream way I can add v1 support > to that, or if it's like this I'll have to make a whole seperate driver > with a whole seperate DT structure. > > Best regards, > David > Best regards, Krzysztof
USIv2 IP-core provides selectable serial protocol (UART, SPI or High-Speed I2C); only one can be chosen at a time. This series implements USIv2 driver, which allows one to select particular USI function in device tree, and also performs USI block initialization. With that driver implemented, it's not needed to do USI initialization in protocol drivers anymore, so that code is removed from the serial driver. Because USI driver is tristate (can be built as a module), serial driver was reworked so it's possible to use its console part as a module too. This way we can load serial driver module from user space and still have serial console functional. Make it impossible to build UART/SPI/I2C driver as a built-in when USIv2 driver built as a module: USIv2 configuration must be always done before tinkering with particular protocol it implements. Design features: - "reg" property contains USI registers start address (0xc0 offset); it's used in the driver to access USI_CON and USI_OPTION registers. This way all USI initialization (reset, HWACG, etc) can be done in USIv2 driver separately, rather than duplicating that code over UART/SPI/I2C drivers - System Register (system controller node) and its SW_CONF register offset are provided in "samsung,sysreg" property; it's used to select USI function (protocol to be used) - USI function is specified in "samsung,mode" property; integer value is used to simplify parsing - there is "samsung,clkreq-on" bool property, which makes driver disable HWACG control (needed for UART to work properly) - PCLK and IPCLK clocks are both provided to USI node; apparently both need to be enabled to access USI registers - protocol nodes are embedded (as a child nodes) in USI node; it allows correct init order, and reflects HW properly - USIv2 driver is a tristate: can be also useful from Android GKI requirements point of view - driver functions are implemented with further development in mind: we might want to add some SysFS interface later for example, or provide some functions to serial drivers with EXPORT_SYMBOL(), etc Sam Protsenko (8): dt-bindings: soc: samsung: Add Exynos USIv2 bindings dt-bindings: soc: samsung: Add Exynos USIv2 bindings doc soc: samsung: Add USIv2 driver tty: serial: samsung: Remove USI initialization tty: serial: samsung: Enable console as module tty: serial: Make SERIAL_SAMSUNG=y impossible when EXYNOS_USI_V2=m i2c: Make I2C_EXYNOS5=y impossible when EXYNOS_USI_V2=m spi: Make SPI_S3C64XX=y impossible when EXYNOS_USI_V2=m .../bindings/soc/samsung/exynos-usi-v2.yaml | 124 +++++++++ drivers/i2c/busses/Kconfig | 1 + drivers/soc/samsung/Kconfig | 14 + drivers/soc/samsung/Makefile | 2 + drivers/soc/samsung/exynos-usi-v2.c | 242 ++++++++++++++++++ drivers/spi/Kconfig | 1 + drivers/tty/serial/Kconfig | 3 +- drivers/tty/serial/samsung_tty.c | 57 ++--- .../dt-bindings/soc/samsung,exynos-usi-v2.h | 16 ++ include/linux/serial_s3c.h | 9 - 10 files changed, 425 insertions(+), 44 deletions(-) create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi-v2.yaml create mode 100644 drivers/soc/samsung/exynos-usi-v2.c create mode 100644 include/dt-bindings/soc/samsung,exynos-usi-v2.h