Re: [PATCH for-6.0 2/2] aspeed/smc: Add extra controls to request DMA

[Joel Stanley]

On Fri, 20 Nov 2020 at 16:16, Cédric Le Goater <clg@kaod.org> wrote:
>
> The controller has a set of hidden bits to request/grant DMA access.

Do you have the ast2600 datasheet? It describes these bits:

31 RW DMA Request

Write SPIR80 = 0xAEED0000 to set this bit ot '1'.
And hardware will clear the request to '0' after DMA done, or FW can
clear to '0' by writing SPIR80 = 0xDEEA0000.

30 RO DMA Grant

0: DMA is not allowed to be used. All DMA related control registers
are not allowed to be written.
1: DMA is granted to be used.

Do you want to add the magic behavior to your model?

>
> Cc: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
>  hw/ssi/aspeed_smc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/hw/ssi/aspeed_smc.c b/hw/ssi/aspeed_smc.c
> index e3d5e26058c0..c1557ef5d848 100644
> --- a/hw/ssi/aspeed_smc.c
> +++ b/hw/ssi/aspeed_smc.c
> @@ -127,6 +127,8 @@
>
>  /* DMA Control/Status Register */
>  #define R_DMA_CTRL        (0x80 / 4)
> +#define   DMA_CTRL_REQUEST      (1 << 31)
> +#define   DMA_CTRL_GRANT        (1 << 30)
>  #define   DMA_CTRL_DELAY_MASK   0xf
>  #define   DMA_CTRL_DELAY_SHIFT  8
>  #define   DMA_CTRL_FREQ_MASK    0xf
> @@ -1237,6 +1239,11 @@ static void aspeed_smc_dma_done(AspeedSMCState *s)
>
>  static void aspeed_smc_dma_ctrl(AspeedSMCState *s, uint64_t dma_ctrl)
>  {
> +    if (dma_ctrl & DMA_CTRL_REQUEST) {
> +            s->regs[R_DMA_CTRL] = dma_ctrl | DMA_CTRL_GRANT;
> +            return;
> +    }
> +
>      if (!(dma_ctrl & DMA_CTRL_ENABLE)) {
>          s->regs[R_DMA_CTRL] = dma_ctrl;
>
> --
> 2.26.2
>