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

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Date:   Mon, 8 May 2023 10:57:55 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Tom Rix <trix@...hat.com>, chunkuang.hu@...nel.org,
        p.zabel@...gutronix.de, chunfeng.yun@...iatek.com,
        vkoul@...nel.org, kishon@...nel.org,
        angelogioacchino.delregno@...labora.com
Cc:     dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] phy: mediatek: rework the floating point comparisons
 to fixed point



On 02/05/2023 16:50, Tom Rix wrote:
> 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>

I think this is worth a fixes tag.

Regards,
Matthias

> ---
> 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;