Re: [PATCH] phy: mediatek: Avoid floating point constants

[Vinod Koul <vkoul@kernel.org>]

On 17-05-23, 12:59, Jon Hunter wrote:
> Hi Vinod,
> 
> On 19/04/2023 13:21, Thierry Reding wrote:
> > From: Thierry Reding <treding@nvidia.com>
> > 
> > When building with old versions of GCC (6.3 in this case), the compiler
> > stumbles over the floating point constants in this driver:
> > 
> > 	: In function ‘mtk_hdmi_pll_prepare’:
> > 	drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c:331:23: error: ‘-mgeneral-regs-only’ is incompatible with floating-point code
> > 	  } else if (pixel_clk >= 74.175 * MEGA && pixel_clk <= 300 * MEGA) {
> > 
> > 	drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c:361:12: error: ‘-mgeneral-regs-only’ is incompatible with floating-point code
> > 	 static int mtk_hdmi_pll_prepare(struct clk_hw *hw)
> > 		    ^~~~~~~~~~~~~~~~~~~~
> > 	drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c:361:12: error: ‘-mgeneral-regs-only’ is incompatible with floating-point code
> > 
> > Fix this by switching to the KILO macro instead and multiplying the
> > constants by 1000 to get rid of the floating point.
> > 
> > Fixes: 45810d486bb4 ("phy: mediatek: add support for phy-mtk-hdmi-mt8195")
> > Reported-by: Jonathan Hunter <jonathanh@nvidia.com>
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> >   drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> > index abfc077fb0a8..b10af26cad2f 100644
> > --- a/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> > +++ b/drivers/phy/mediatek/phy-mtk-hdmi-mt8195.c
> > @@ -239,9 +239,9 @@ static int mtk_hdmi_pll_calc(struct mtk_hdmi_phy *hdmi_phy, struct clk_hw *hw,
> >   		txposdiv = 8;
> >   	else if (tmds_clk >= 54 * MEGA && tmds_clk < 148.35 * MEGA)
> >   		txposdiv = 4;
> > -	else if (tmds_clk >= 148.35 * MEGA && tmds_clk < 296.7 * MEGA)
> > +	else if (tmds_clk >= 148350 * KILO && tmds_clk < 296700 * KILO)
> >   		txposdiv = 2;
> > -	else if (tmds_clk >= 296.7 * MEGA && tmds_clk <= 594 * MEGA)
> > +	else if (tmds_clk >= 296700 * KILO && 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 (pixel_clk >= 74175 * KILO && 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 && pixel_clk < 74175 * KILO) {
> >   		data_channel_bias = 0x14; /* 10mA */
> >   		clk_channel_bias = 0x14; /* 10mA */
> >   		impedance_en = 0x0;
> 
> 
> This is breaking kernel compilation with older compilers such as GCC7. This
> is now in the mainline and older compilers cannot build the kernel with this
> driver enabled. The kernel docs say the min version supported is GCC 5.1
> currently.
> 
> Can we get this merged as a fix for v6.4?

Sorry I missed this one but I have already applied 03262a3f5b5b ("phy:
mediatek: rework the floating point comparisons to fixed point") and
this is in linux-next and should be hopefully in Linus's tree in next rc

Thanks
-- 
~Vinod

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