linux-kernel - Re: [PATCH][next] drm/amd/pp: initialized result to zero before or'ing in data

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Date:   Wed, 6 Jun 2018 13:19:25 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Zhou <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>, Rex Zhu <Rex.Zhu@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] drm/amd/pp: initialized result to zero before
 or'ing in data

On 06/06/18 13:18, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The current use of result is or'ing in values and checking for
> a non-zero result, however, result is not initialized to zero
> so it potentially contains garbage to start with. Fix this by
> initializing it to the first return from the call to
> vega10_program_didt_config_registers.
> 
> Detected by cppcheck:
> "(error) Uninitialized variable: result"
> 
> Fixes: 9b7b8154cdb8 ("drm/amd/powerplay: added didt support for vega10")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/amd/powerplay/hwmgr/vega10_powertune.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_powertune.c b/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_powertune.c
> index a9efd8554fbc..dbe4b1f66784 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_powertune.c
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_powertune.c
> @@ -1104,7 +1104,7 @@ static int vega10_enable_psm_gc_edc_config(struct pp_hwmgr *hwmgr)
>  	for (count = 0; count < num_se; count++) {
>  		data = GRBM_GFX_INDEX__INSTANCE_BROADCAST_WRITES_MASK | GRBM_GFX_INDEX__SH_BROADCAST_WRITES_MASK | ( count << GRBM_GFX_INDEX__SE_INDEX__SHIFT);
>  		WREG32_SOC15(GC, 0, mmGRBM_GFX_INDEX, data);
> -		result |= vega10_program_didt_config_registers(hwmgr, PSMSEEDCStallPatternConfig_Vega10, VEGA10_CONFIGREG_DIDT);
> +		result = vega10_program_didt_config_registers(hwmgr, PSMSEEDCStallPatternConfig_Vega10, VEGA10_CONFIGREG_DIDT);
>  		result |= vega10_program_didt_config_registers(hwmgr, PSMSEEDCStallDelayConfig_Vega10, VEGA10_CONFIGREG_DIDT);
>  		result |= vega10_program_didt_config_registers(hwmgr, PSMSEEDCCtrlResetConfig_Vega10, VEGA10_CONFIGREG_DIDT);
>  		result |= vega10_program_didt_config_registers(hwmgr, PSMSEEDCCtrlConfig_Vega10, VEGA10_CONFIGREG_DIDT);
> 

Oops, subject should be "initialize result to before or'ing in data"