Re: [PATCH 2/3] peci: aspeed: Auto calculate the adapter divisor

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Hi Billy,

On Fri, 16 Oct 2020 at 06:26, Billy Tsai <billy_tsai@xxxxxxxxxxxxxx> wrote:
>
> This pach change the meaning of clk-frequency property from original
> controller clock to bit frequency of peci negotiation stage and auto
> calculate the adapter divisor setting to close aim.
> The expected frequency and real frequency may have errors because of the
> granularities of the divisor.

This patch can't go to the mainline lists as the authors (Intel) have
not yet had it merged.

Cheers,

Joel

>
> Signed-off-by: Billy Tsai <billy_tsai@xxxxxxxxxxxxxx>
> ---
>  arch/arm/boot/dts/aspeed-g6.dtsi  |  4 +-
>  drivers/peci/busses/peci-aspeed.c | 91 ++++++++++++++++++-------------
>  2 files changed, 53 insertions(+), 42 deletions(-)
>
> diff --git a/arch/arm/boot/dts/aspeed-g6.dtsi b/arch/arm/boot/dts/aspeed-g6.dtsi
> index cb053a996e87..6e1e5b5733e6 100644
> --- a/arch/arm/boot/dts/aspeed-g6.dtsi
> +++ b/arch/arm/boot/dts/aspeed-g6.dtsi
> @@ -750,9 +750,7 @@
>                 interrupts = <GIC_SPI 38 IRQ_TYPE_LEVEL_HIGH>;
>                 clocks = <&syscon ASPEED_CLK_GATE_REF0CLK>;
>                 resets = <&syscon ASPEED_RESET_PECI>;
> -               clock-frequency = <24000000>;
> -               msg-timing = <1>;
> -               addr-timing = <1>;
> +               clock-frequency = <1000000>;
>                 rd-sampling-point = <8>;
>                 cmd-timeout-ms = <1000>;
>                 status = "disabled";
> diff --git a/drivers/peci/busses/peci-aspeed.c b/drivers/peci/busses/peci-aspeed.c
> index d6039b1c4494..9e7c7582e4bb 100644
> --- a/drivers/peci/busses/peci-aspeed.c
> +++ b/drivers/peci/busses/peci-aspeed.c
> @@ -133,6 +133,11 @@
>  #define ASPEED_PECI_64B_R_DATAE  0xF8
>  #define ASPEED_PECI_64B_R_DATAF  0xFC
>
> +/* Bus Frequency */
> +#define ASPEED_PECI_BUS_FREQ_MAX       2000000
> +#define ASPEED_PECI_BUS_FREQ_MIN       2000
> +#define ASPEED_PECI_BUS_FREQ_DEFAULT   1000000
> +
>  /* Timing Negotiation */
>  #define ASPEED_PECI_RD_SAMPLING_POINT_DEFAULT  8
>  #define ASPEED_PECI_RD_SAMPLING_POINT_MAX      15
> @@ -324,51 +329,47 @@ static irqreturn_t aspeed_peci_irq_handler(int irq, void *arg)
>  static int aspeed_peci_init_ctrl(struct aspeed_peci *priv)
>  {
>         u32 msg_timing, addr_timing, rd_sampling_point;
> -       u32 clk_freq, clk_divisor, clk_div_val = 0;
> +       u32 clk_freq, clk_div_val = 0;
> +       u32 msg_timing_idx, clk_div_val_idx;
> +       int delta_value, delta_tmp, clk_divisor, clk_divisor_tmp;
>         int ret;
>
> -       priv->clk = devm_clk_get(priv->dev, NULL);
> -       if (IS_ERR(priv->clk)) {
> -               dev_err(priv->dev, "Failed to get clk source.\n");
> -               return PTR_ERR(priv->clk);
> -       }
> -
> -       ret = clk_prepare_enable(priv->clk);
> -       if (ret) {
> -               dev_err(priv->dev, "Failed to enable clock.\n");
> -               return ret;
> -       }
> -
>         ret = device_property_read_u32(priv->dev, "clock-frequency", &clk_freq);
> -       if (ret) {
> -               dev_err(priv->dev,
> -                       "Could not read clock-frequency property.\n");
> -               clk_disable_unprepare(priv->clk);
> -               return ret;
> -       }
> -
> -       clk_divisor = clk_get_rate(priv->clk) / clk_freq;
> -
> -       while ((clk_divisor >> 1) && (clk_div_val < ASPEED_PECI_CLK_DIV_MAX))
> -               clk_div_val++;
> -
> -       ret = device_property_read_u32(priv->dev, "msg-timing", &msg_timing);
> -       if (ret || msg_timing > ASPEED_PECI_MSG_TIMING_MAX) {
> +       if (ret ||
> +       clk_freq > ASPEED_PECI_BUS_FREQ_MAX ||
> +       clk_freq < ASPEED_PECI_BUS_FREQ_MIN) {
>                 if (!ret)
>                         dev_warn(priv->dev,
> -                                "Invalid msg-timing : %u, Use default : %u\n",
> -                                msg_timing, ASPEED_PECI_MSG_TIMING_DEFAULT);
> -               msg_timing = ASPEED_PECI_MSG_TIMING_DEFAULT;
> -       }
> -
> -       ret = device_property_read_u32(priv->dev, "addr-timing", &addr_timing);
> -       if (ret || addr_timing > ASPEED_PECI_ADDR_TIMING_MAX) {
> -               if (!ret)
> -                       dev_warn(priv->dev,
> -                                "Invalid addr-timing : %u, Use default : %u\n",
> -                                addr_timing, ASPEED_PECI_ADDR_TIMING_DEFAULT);
> -               addr_timing = ASPEED_PECI_ADDR_TIMING_DEFAULT;
> +                                "Invalid clock-frequency : %u, Use default : %u\n",
> +                                clk_freq, ASPEED_PECI_BUS_FREQ_DEFAULT);
> +               clk_freq = ASPEED_PECI_BUS_FREQ_DEFAULT;
>         }
> +       /*
> +        * PECI bus clock = (Ref. clk) / (1 << PECI00[10:8])
> +        * PECI operation clock = (PECI bus clock)/ 4*(PECI04[15:8]*4+1)
> +        * (1 << PECI00[10:8]) * (PECI04[15:8]*4+1) =
> +        * (Ref. clk) / (4 * PECI operation clock)
> +        */
> +       clk_divisor = clk_get_rate(priv->clk) / (4*clk_freq);
> +       delta_value = clk_divisor;
> +       /* Find the closest divisor for clock-frequency */
> +       for (msg_timing_idx = 1; msg_timing_idx <= 255; msg_timing_idx++)
> +               for (clk_div_val_idx = 0; clk_div_val_idx < 7;
> +                       clk_div_val_idx++) {
> +                       clk_divisor_tmp = (1 << clk_div_val_idx) *
> +                                       (msg_timing_idx * 4 + 1);
> +                       delta_tmp = abs(clk_divisor - clk_divisor_tmp);
> +                       if (delta_tmp < delta_value) {
> +                               delta_value = delta_tmp;
> +                               msg_timing = msg_timing_idx;
> +                               clk_div_val = clk_div_val_idx;
> +                       }
> +               }
> +       addr_timing = msg_timing;
> +       dev_info(priv->dev, "Expect frequency: %d Real frequency is about: %lu",
> +               clk_freq,
> +               clk_get_rate(priv->clk) /
> +               (4 * (1 << clk_div_val) * (msg_timing * 4 + 1)));
>
>         ret = device_property_read_u32(priv->dev, "rd-sampling-point",
>                                        &rd_sampling_point);
> @@ -463,6 +464,18 @@ static int aspeed_peci_probe(struct platform_device *pdev)
>         priv->adapter->xfer = aspeed_peci_xfer;
>         priv->adapter->use_dma = false;
>
> +       priv->clk = devm_clk_get(priv->dev, NULL);
> +       if (IS_ERR(priv->clk)) {
> +               dev_err(priv->dev, "Failed to get clk source.\n");
> +               return PTR_ERR(priv->clk);
> +       }
> +
> +       ret = clk_prepare_enable(priv->clk);
> +       if (ret) {
> +               dev_err(priv->dev, "Failed to enable clock.\n");
> +               return ret;
> +       }
> +
>         priv->rst = devm_reset_control_get(&pdev->dev, NULL);
>         if (IS_ERR(priv->rst)) {
>                 dev_err(&pdev->dev,
> --
> 2.17.1
>



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