linux-kernel - Re: [PATCH v2] phy: mediatek: rework the floating point comparisons to fixed point

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Date:   Thu, 4 May 2023 07:53:33 +0000
From:   Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>
To:     "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "trix@...hat.com" <trix@...hat.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "kishon@...nel.org" <kishon@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] phy: mediatek: rework the floating point comparisons
 to fixed point

On Tue, 2023-05-02 at 10:50 -0400, Tom Rix wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> gcc on aarch64 reports
> drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c: In function
> ‘mtk_hdmi_pll_set_rate’:
> drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c:240:52: error: ‘-mgeneral-
> regs-only’
>   is incompatible with the use of floating-point types
>   240 |         else if (tmds_clk >= 54 * MEGA && tmds_clk < 148.35 *
> MEGA)
> 
> Floating point should not be used, so rework the floating point
> comparisons
> to fixed point.
> 
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
> v2: silence robot by casting types to u64
> 
> ---
> drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> index abfc077fb0a8..093c4d1da557 100644
> --- a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> +++ b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> @@ -237,11 +237,11 @@ static int mtk_hdmi_pll_calc(struct
> mtk_hdmi_phy *hdmi_phy, struct clk_hw *hw,
>          */
>         if (tmds_clk < 54 * MEGA)
>                 txposdiv = 8;
> -       else if (tmds_clk >= 54 * MEGA && tmds_clk < 148.35 * MEGA)
> +       else if (tmds_clk >= 54 * MEGA && (tmds_clk * 100) < 14835 *
> MEGA)
>                 txposdiv = 4;
> -       else if (tmds_clk >= 148.35 * MEGA && tmds_clk < 296.7 *
> MEGA)
> +       else if ((tmds_clk * 100) >= 14835 * MEGA && (tmds_clk * 10)
> < 2967 * MEGA)
>                 txposdiv = 2;
> -       else if (tmds_clk >= 296.7 * MEGA && tmds_clk <= 594 * MEGA)
> +       else if ((tmds_clk * 10) >= 2967 * MEGA && tmds_clk <= 594 *
> MEGA)
>                 txposdiv = 1;
>         else
>                 return -EINVAL;
> @@ -328,12 +328,12 @@ static int mtk_hdmi_pll_drv_setting(struct
> clk_hw *hw)
>                 clk_channel_bias = 0x34; /* 20mA */
>                 impedance_en = 0xf;
>                 impedance = 0x36; /* 100ohm */
> -       } else if (pixel_clk >= 74.175 * MEGA && pixel_clk <= 300 *
> MEGA) {
> +       } else if (((u64)pixel_clk * 1000) >= 74175 * MEGA &&
> pixel_clk <= 300 * MEGA) {
>                 data_channel_bias = 0x34; /* 20mA */
>                 clk_channel_bias = 0x2c; /* 16mA */
>                 impedance_en = 0xf;
>                 impedance = 0x36; /* 100ohm */
> -       } else if (pixel_clk >= 27 * MEGA && pixel_clk < 74.175 *
> MEGA) {
> +       } else if (pixel_clk >= 27 * MEGA && ((u64)pixel_clk * 1000)
> < 74175 * MEGA) {
>                 data_channel_bias = 0x14; /* 10mA */
>                 clk_channel_bias = 0x14; /* 10mA */
>                 impedance_en = 0x0;
> --
> 2.27.0

Reviewed-by: Chunfeng Yun <chunfeng.yun@...iatek.com>

Thanks
>