linux-kernel - Re: [PATCH 3/6] drm/meson: venc: add ENCL encoder setup for MIPI-DSI output

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Message-ID: <6f62eeaa-1feb-274a-e1e8-377c582c428f@baylibre.com>
Date:   Mon, 10 Jan 2022 10:45:58 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] drm/meson: venc: add ENCL encoder setup for MIPI-DSI
 output

On 07/01/2022 23:33, Martin Blumenstingl wrote:
>  Hi Neil,
> 
> On Fri, Jan 7, 2022 at 3:57 PM Neil Armstrong <narmstrong@...libre.com> wrote:
>>
>> This adds supports for the ENCL encoder connected to a MIPI-DSI transceiver on the
>> Amlogic AXG SoCs> Should this be "AXG and newer SoCs" or is this really AXG specific?

Yup should be, thanks for noting

> 
> [...]
>> +#define GAMMA_VCOM_POL    7     /* RW */
>> +#define GAMMA_RVS_OUT     6     /* RW */
>> +#define ADR_RDY           5     /* Read Only */
>> +#define WR_RDY            4     /* Read Only */
>> +#define RD_RDY            3     /* Read Only */
>> +#define GAMMA_TR          2     /* RW */
>> +#define GAMMA_SET         1     /* RW */
>> +#define GAMMA_EN          0     /* RW */
>> +
>> +#define H_RD              12
>> +#define H_AUTO_INC        11
>> +#define H_SEL_R           10
>> +#define H_SEL_G           9
>> +#define H_SEL_B           8
> I think all values above can be wrapped in the BIT() macro, then you
> don't need that below.

yep

> 
>> +#define HADR_MSB          7            /* 7:0 */
>> +#define HADR              0            /* 7:0 */
> Here GENMASK(7, 0) can be used for HADR
> 
> Also I think prefixing all macros above with their register name
> (L_GAMMA_CNTL_PORT_ or L_GAMMA_ADDR_PORT_) will make the code easier
> to read.
> 
> [...]
>> +       writel_relaxed(0x8000, priv->io_base + _REG(ENCL_VIDEO_MODE));
> The public S905 datasheet calls 0x8000 ENCL_PX_LN_CNT_SHADOW_EN

Thanks for searching !

> 
>> +       writel_relaxed(0x0418, priv->io_base + _REG(ENCL_VIDEO_MODE_ADV));
> According to the public S905 datasheet this is:
> - BIT(3): ENCL_VIDEO_MODE_ADV_VFIFO_EN
> - BIT(4): ENCL_VIDEO_MODE_ADV_GAIN_HDTV
> - BIT(10): ENCL_SEL_GAMMA_RGB_IN
> 
>> +       writel_relaxed(0x1000, priv->io_base + _REG(ENCL_VIDEO_FILT_CTRL));
> I don't know the exact name but the 32-bit vendor kernel sources have
> a comment [0] saying that 0x1000 is "bypass filter"
> But maybe we can simply call it ENCL_VIDEO_FILT_CTRL_BYPASS_FILTER

Yep

> 
> [...]
>> +       writel_relaxed(3, priv->io_base + _REG(ENCL_VIDEO_RGBIN_CTRL));
> The public S905 datasheet says:
> - BIT(0): USE RGB data from VIU, furthermore a comment in the 3.10
> kernel sources make this more clear: bit[0] 1:RGB, 0:YUV
> - BIT(1): CFG_VIDEO_RGBIN_ZBLK
> 
>> +       /* default black pattern */
>> +       writel_relaxed(0, priv->io_base + _REG(ENCL_TST_MDSEL));
>> +       writel_relaxed(0, priv->io_base + _REG(ENCL_TST_Y));
>> +       writel_relaxed(0, priv->io_base + _REG(ENCL_TST_CB));
>> +       writel_relaxed(0, priv->io_base + _REG(ENCL_TST_CR));
>> +       writel_relaxed(1, priv->io_base + _REG(ENCL_TST_EN));
>> +       writel_bits_relaxed(BIT(3), 0, priv->io_base + _REG(ENCL_VIDEO_MODE_ADV));
> same as above: ENCL_VIDEO_MODE_ADV_VFIFO_EN
> 
>> +
>> +       writel_relaxed(1, priv->io_base + _REG(ENCL_VIDEO_EN));
>> +
>> +       writel_relaxed(0, priv->io_base + _REG(L_RGB_BASE_ADDR));
>> +       writel_relaxed(0x400, priv->io_base + _REG(L_RGB_COEFF_ADDR));
> note to self: L_RGB_COEFF_ADDR seems to contain some "magic" value,
> there's no further info in the 3.10 kernel sources or datasheet
> 
>> +       writel_relaxed(0x400, priv->io_base + _REG(L_DITH_CNTL_ADDR));
> According to the public S905 datasheet BIT(10) is DITH10_EN (10-bits
> Dithering to 8 Bits Enable).
> I am not sure if this would belong to the selected video mode/bit depth.
> I'll let other reviewers decide if this is relevant or not because I don't know.


it would probably for pre-GXL when the pipeline was 8bit, would probably need to add
a comment if someone wants to us DPI/LVDS on pre-GXL.

> 
> [...]
>> +       writel_relaxed(0, priv->io_base + _REG(L_INV_CNT_ADDR));
>> +       writel_relaxed(BIT(4) | BIT(5),
>> +                      priv->io_base + _REG(L_TCON_MISC_SEL_ADDR));
> the public S905 datasheet states:
> - BIT(4): STV1_SEL (STV1 is frame Signal)
> - BIT(5): STV2_SEL (STV2 is frame Signal)
> This doesn't seem helpful to me though, but maybe you can still create
> preprocessor macros for this (for consistency)?

yep

> 
> [...]
>> +       switch (priv->venc.current_mode) {
>> +       case MESON_VENC_MODE_MIPI_DSI:
>> +               writel_relaxed(0x200,
>> +                              priv->io_base + _REG(VENC_INTCTRL));
> the public S905 datasheet documents this as:
> - BIT(9): ENCP_LNRST_INT_EN (Progressive encoder filed change interrupt enable)
> Please add a preprocessor macro to make it consistent with
> VENC_INTCTRL_ENCI_LNRST_INT_EN which already exists and is used below.

Yep

Thanks for the review :-)

Neil

> 
> 
> Best regards,
> Martin
>