linux-kernel - Re: [PATCH 2/4] drm/bridge: add Microchip DSI controller support for sam9x7 SoC series

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Message-ID: <4c1b7af7-e53c-492a-9c41-40cad78f7666@kernel.org>
Date: Thu, 11 Jul 2024 11:05:37 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Manikandan.M@...rochip.com
Cc: Hari.PrasathGE@...rochip.com, andrzej.hajda@...el.com,
 neil.armstrong@...aro.org, rfoss@...nel.org,
 Laurent.pinchart@...asonboard.com, jonas@...boo.se,
 jernej.skrabec@...il.com, airlied@...il.com, daniel@...ll.ch,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de,
 robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 linux@...linux.org.uk, Nicolas.Ferre@...rochip.com,
 alexandre.belloni@...tlin.com, claudiu.beznea@...on.dev, arnd@...db.de,
 Jason@...c4.com, palmer@...osinc.com, mpe@...erman.id.au,
 rdunlap@...radead.org, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] drm/bridge: add Microchip DSI controller support for
 sam9x7 SoC series

On 11/07/2024 10:30, Manikandan.M@...rochip.com wrote:
> Hi Krzysztof,
> 
> On 04/07/24 4:27 pm, Krzysztof Kozlowski wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> On 04/07/2024 10:48, Manikandan Muralidharan wrote:
>>> Add the Microchip's DSI controller wrapper driver that uses
>>> the Synopsys DesignWare MIPI DSI host controller bridge.
>>>
>>> Signed-off-by: Manikandan Muralidharan <manikandan.m@...rochip.com>
>>> ---
>>
>>
>> ...
>>
>>> +
>>> +#define HSTT(_maxfreq, _c_lp2hs, _c_hs2lp, _d_lp2hs, _d_hs2lp)       \
>>> +{                                    \
>>> +     .maxfreq = _maxfreq,            \
>>> +     .timing = {                     \
>>> +             .clk_lp2hs = _c_lp2hs,  \
>>> +             .clk_hs2lp = _c_hs2lp,  \
>>> +             .data_lp2hs = _d_lp2hs, \
>>> +             .data_hs2lp = _d_hs2lp, \
>>> +     }                               \
>>> +}
>>> +
>>> +struct hstt hstt_table[] = {
>>
>> So more globals? No.
> 
> In the sam9x7 datasheet, the high speed transition time for data and
> clock lane at different freq for the DSI controller ranges are tabulated
> with constant values.
> I referred other similar platforms for the functionality and found 
> similar way of implementation,  only a few had equations to derive the 
> low power and high speed timings.I am not able to come up with a more 
> efficient method. If there is something I am missing, please suggest.
> TIA

Yeah, this should not be a global. Nothing above suggests it.

BTW, no W=1 clang warnings? Are you sure?

Best regards,
Krzysztof