linux-kernel - Re: [PATCH] drm/stm: dsi: compute the transition time from LP to HS and back

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Date:   Mon, 19 Jul 2021 15:40:39 +0200
From:   Philippe CORNU <philippe.cornu@...s.st.com>
To:     Antonio Borneo <antonio.borneo@...s.st.com>,
        Yannick Fertre <yannick.fertre@...s.st.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/stm: dsi: compute the transition time from LP to HS
 and back



On 7/13/21 6:47 PM, Philippe CORNU wrote:
> Hi Antonio,
> 
> On 7/13/21 4:49 PM, Antonio Borneo wrote:
>> The driver uses a conservative set of hardcoded values for the
>> maximum time delay of the transitions between LP and HS, either
>> for data and clock lanes.
>>
>> By using the info in STM32MP157 datasheet, valid also for other ST
>> devices, compute the actual delay from the lane's bps.
>>
>> Signed-off-by: Antonio Borneo <antonio.borneo@...s.st.com>
>> ---
>> To: Yannick Fertre <yannick.fertre@...s.st.com>
>> To: Philippe Cornu <philippe.cornu@...s.st.com>
>> To: Benjamin Gaignard <benjamin.gaignard@...aro.org>
>> To: David Airlie <airlied@...ux.ie>
>> To: Daniel Vetter <daniel@...ll.ch>
>> To: Maxime Coquelin <mcoquelin.stm32@...il.com>
>> To: Alexandre Torgue <alexandre.torgue@...s.st.com>
>> To: Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>
>> To: dri-devel@...ts.freedesktop.org
>> To: linux-stm32@...md-mailman.stormreply.com
>> To: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>>
>>   drivers/gpu/drm/stm/dw_mipi_dsi-stm.c | 17 +++++++++++++----
>>   1 file changed, 13 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c 
>> b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
>> index 8399d337589d..32cb41b2202f 100644
>> --- a/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
>> +++ b/drivers/gpu/drm/stm/dw_mipi_dsi-stm.c
>> @@ -309,14 +309,23 @@ dw_mipi_dsi_get_lane_mbps(void *priv_data, const 
>> struct drm_display_mode *mode,
>>       return 0;
>>   }
>> +#define DSI_PHY_DELAY(fp, vp, mbps) DIV_ROUND_UP((fp) * (mbps) + 1000 
>> * (vp), 8000)
>> +
>>   static int
>>   dw_mipi_dsi_phy_get_timing(void *priv_data, unsigned int lane_mbps,
>>                  struct dw_mipi_dsi_dphy_timing *timing)
>>   {
>> -    timing->clk_hs2lp = 0x40;
>> -    timing->clk_lp2hs = 0x40;
>> -    timing->data_hs2lp = 0x40;
>> -    timing->data_lp2hs = 0x40;
>> +    /*
>> +     * From STM32MP157 datasheet, valid for STM32F469, STM32F7x9, 
>> STM32H747
>> +     * phy_clkhs2lp_time = (272+136*UI)/(8*UI)
>> +     * phy_clklp2hs_time = (512+40*UI)/(8*UI)
>> +     * phy_hs2lp_time = (192+64*UI)/(8*UI)
>> +     * phy_lp2hs_time = (256+32*UI)/(8*UI)
>> +     */
>> +    timing->clk_hs2lp = DSI_PHY_DELAY(272, 136, lane_mbps);
>> +    timing->clk_lp2hs = DSI_PHY_DELAY(512, 40, lane_mbps);
>> +    timing->data_hs2lp = DSI_PHY_DELAY(192, 64, lane_mbps);
>> +    timing->data_lp2hs = DSI_PHY_DELAY(256, 32, lane_mbps);
> 
> Many thanks for your patch.
> 
> Reviewed-by: Philippe Cornu <philippe.cornu@...s.st.com>
> Acked-by: Philippe Cornu <philippe.cornu@...s.st.com>
> 
> I will apply it on drm-misc-next early next week,
> 
> Philippe :-)
> 
>>       return 0;
>>   }
>>
>> base-commit: 35d283658a6196b2057be562096610c6793e1219
>>

Applied on drm-misc-next.
Many thanks for your patch,
Philippe :-)