linux-kernel - Re: [PATCH 14/31] video: fbdev: aty: mach64_ct: Remove some set but unused variables

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Date:   Wed, 13 Jan 2021 16:24:22 +0100 (CET)
From:   Daniël Mantione 
        <daniel.mantione@...epascal.org>
To:     Lee Jones <lee.jones@...aro.org>
cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 14/31] video: fbdev: aty: mach64_ct: Remove some set but
 unused variables

Hi,

If I remember well, the removed lines have to do with the VGA/accelerator 
mode of the chip. The current driver always runs the chip in accelerator 
mode. Suppose you would want to support high resolution hardware text 
modes with the driver (fbdev bpp=0), then you would need to switch the 
chip into VGA mode mode and then the removed lines become relevant.

I did some experiments with this when I was working on the driver, but 
because the documentation was silent about the behaviour of extended 
CRTC registers in VGA mode, I failed to make hardware text modes to work 
properly.

The #if 0 was there so code was already there in case me or someone else 
would pick it up again.

Best regards,

Daniël Mantione

Op Wed, 13 Jan 2021, schreef Lee Jones:

> Fixes the following W=1 kernel build warning(s):
>
> drivers/video/fbdev/aty/mach64_ct.c: In function ‘aty_init_pll_ct’:
> drivers/video/fbdev/aty/mach64_ct.c:405:46: warning: variable ‘vga_dsp_on_off’ set but not used [-Wunused-but-set-variable]
> drivers/video/fbdev/aty/mach64_ct.c:405:30: warning: variable ‘vga_dsp_config’ set but not used [-Wunused-but-set-variable]
> drivers/video/fbdev/aty/mach64_ct.c:405:18: warning: variable ‘dsp_on_off’ set but not used [-Wunused-but-set-variable]
>
> Cc: daniel.mantione@...epascal.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-fbdev@...r.kernel.org
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
> drivers/video/fbdev/aty/mach64_ct.c | 19 ++-----------------
> 1 file changed, 2 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/video/fbdev/aty/mach64_ct.c b/drivers/video/fbdev/aty/mach64_ct.c
> index f87cc81f4fa2b..23eececa1e9d7 100644
> --- a/drivers/video/fbdev/aty/mach64_ct.c
> +++ b/drivers/video/fbdev/aty/mach64_ct.c
> @@ -402,7 +402,7 @@ static int aty_init_pll_ct(const struct fb_info *info, union aty_pll *pll)
> 	struct atyfb_par *par = (struct atyfb_par *) info->par;
> 	u8 mpost_div, xpost_div, sclk_post_div_real;
> 	u32 q, memcntl, trp;
> -	u32 dsp_config, dsp_on_off, vga_dsp_config, vga_dsp_on_off;
> +	u32 dsp_config;
> #ifdef DEBUG
> 	int pllmclk, pllsclk;
> #endif
> @@ -488,25 +488,10 @@ static int aty_init_pll_ct(const struct fb_info *info, union aty_pll *pll)
>
> 	/* Allow BIOS to override */
> 	dsp_config = aty_ld_le32(DSP_CONFIG, par);
> -	dsp_on_off = aty_ld_le32(DSP_ON_OFF, par);
> -	vga_dsp_config = aty_ld_le32(VGA_DSP_CONFIG, par);
> -	vga_dsp_on_off = aty_ld_le32(VGA_DSP_ON_OFF, par);
>
> 	if (dsp_config)
> 		pll->ct.dsp_loop_latency = (dsp_config & DSP_LOOP_LATENCY) >> 16;
> -#if 0
> -	FIXME: is it relevant for us?
> -	if ((!dsp_on_off && !M64_HAS(RESET_3D)) ||
> -		((dsp_on_off == vga_dsp_on_off) &&
> -		(!dsp_config || !((dsp_config ^ vga_dsp_config) & DSP_XCLKS_PER_QW)))) {
> -		vga_dsp_on_off &= VGA_DSP_OFF;
> -		vga_dsp_config &= VGA_DSP_XCLKS_PER_QW;
> -		if (ATIDivide(vga_dsp_on_off, vga_dsp_config, 5, 1) > 24)
> -			pll->ct.fifo_size = 32;
> -		else
> -			pll->ct.fifo_size = 24;
> -	}
> -#endif
> +
> 	/* Exit if the user does not want us to tamper with the clock
> 	rates of her chip. */
> 	if (par->mclk_per == 0) {
> -- 
> 2.25.1
>