Samsung SoCs: preparation for single kernel

[Eric Miao]

On Wednesday, June 23, 2010, Marek Szyprowski <m.szyprowski at samsung.com> wrote:
> Hello,
>
> On Wednesday, June 23, 2010 10:02 AM Eric Miao wrote:
>
>> >> Now you have
>> >>
>> >> s5pv210_device_hsmmc0
>> >> s5pc100_device_hsmmc0
>> >> s3c64xx_device_hsmmc0
>> >> ....
>> >>
>> >> each with a different base.
>> >
>> > There is no need for such code duplication.
>>
>> However, I believe this is the right way to go. A certain level of
>> duplication is the price to pay for a generic and clean solution.
>>
>> When a peripheral controller or IP is moved from one SoC to the
>> next generation, there are several things could have been changed:
>>
>> 1. new base address and IRQ number
>> 2. fixes and enhancements to the original IP
>>
>> 1. will result in a different 'struct resource', and 2. will result in a
>> different 'struct platform_device' with a different name, so the driver
>> can match the platform_device_id table as you agreed I'm right on
>> that recommendation.
>>
>> They are actually _two_ different devices.
>
> Right, they are separate entities, but would be really good if a similar
> git brcode could be merged together.
>
>> > Ben is working on a solution for
>> > a single kernel which supports multiple SoCs. Some of his work in
>> progress can
>> > be found here: git://git.fluff.org/bjdooks/linux branch wip-samsung-dev
>> and
>> > wip-samsung-dev2.
>>
>> Could you describe it a bit here and bring it on table for discussion?
>
> The idea behind his patches is to provide a table for each SoC with short
> description of all available devices and generate platform_device entries
> dynamically from that table.
>
> Here is a short code example:
>
> struct s3c_pdev_table s3c6xxx_dev_table[] __initdata = {
>         {
>                 .type   = SAMSUNG_DEVICE_UART,
>                 .name   = "s3c6400-uart",
>                 .index  = 0,
>                 .base   = S3C_PA_UART0,
>                 .irq    = IRQ_S3CUART_RX0,
>                 .template = &template_uart_s3c64xx,
>         }, {
>                 .type   = SAMSUNG_DEVICE_UART,
>                 .name   = "s3c6400-uart",
>                 .index  = 1,
>                 .base   = S3C_PA_UART1,
>                 .irq    = IRQ_S3CUART_RX1,
>                 .template = &template_uart_s3c64xx,
>         }, {
>                 .type   = SAMSUNG_DEVICE_UART,
>                 .name   = "s3c6400-uart",
>                 .index  = 2,
>                 .base   = S3C_PA_UART2,
>                 .irq    = IRQ_S3CUART_RX2,
>                 .template = &template_uart_s3c64xx,
>         }, {
>                 .type   = SAMSUNG_DEVICE_UART,
>                 .name   = "s3c6400-uart",
>                 .index  = 3,
>                 .base   = S3C_PA_UART3,
>                 .irq    = IRQ_S3CUART_RX3,
>                 .template = &template_uart_s3c64xx,
>         }, {
>                 .type   = SAMSUNG_DEVICE_WATCHDOG,
>                 .name   = "s3c2410-wdt",
>                 .index  = -1,
>                 .base   = S3C64XX_PA_WATCHDOG,
>                 .irq    = IRQ_WDT,
>         }, {
>                 .type   = SAMSUNG_DEVICE_SDHCI,
>                 .name   = "s3c-sdhci",
>                 .index  = 0,
>                 .base   = S3C64XX_PA_HSMMC0 ,
>                 .irq    = IRQ_HSMMC0,
>                 .dma    = &samsung_std_dma_mask,
>         }, {
>                 .type   = SAMSUNG_DEVICE_SDHCI,
>                 .name   = "s3c-sdhci",
>                 .index  = 1,
>                 .base   = S3C64XX_PA_HSMMC1,
>                 .irq    = IRQ_HSMMC1,
>                 .dma    = &samsung_std_dma_mask,
>         }, {
>                 .type   = SAMSUNG_DEVICE_SDHCI,
>                 .name   = "s3c-sdhci",
>                 .index  = 2,
>                 .base   = S3C64XX_PA_HSMMC2,
>                 .irq    = IRQ_HSMMC1,
>                 .dma    = &samsung_std_dma_mask,
>         }, {
>                 .type   = SAMSUNG_DEVICE_OHCI,
>                 .name   = "s3c2410-ohci",
>                 .index  = -1,
>                 .base   = S3C64XX_PA_USBHOST,
>                 .irq    = IRQ_USBH,
>                 .dma    = &samsung_std_dma_mask,
>         }, {
>                 .type   = SAMSUNG_DEVICE_NAND,
>                 .name   = "s3c6400-nand",
>                 .index  = -1,
>                 .base   = 0x4E000000,
>                 .irq    = IRQ_NFC,
>         }, {
>                 .type   = SAMSUNG_DEVICE_I2C,
>                 .name   = "s3c2440-i2c",
>                 .index  = 0,
>                 .base   = S3C64XX_PA_IIC0,
>                 .irq    = IRQ_IIC,
>         }, {
> ...
>
> This solution is imho really clean an easy to understand. It is also
> easy to check which SoC has which peripherals defined and how.
>

Yep, this was already used in arch/arm/mach-mmp, and I wrote that.

It's actually an improved version of multiple platform_device.

> I hope Ben will be able to finish it soon and all Samsung platforms can
> be converted for it. Then creating a single kernel for more than one SoC
> should be possible with only a few additional changes.
>
>> PS: My feeling of commenting several of the samsung patches so far turns
>> out to be quite frustrated, or I'm just too sensitive. NOTE neither am I
>> NAKing Samsung patches, nor am I interested to be involved, I'm just givin
>> my suggestions.
>
> I'm sorry if I offended You. I just wanted to show that the solution has
> been already found.
>
> Best regards
> --
> Marek Szyprowski
> Samsung Poland R&D Center
>
>
>
>