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Message-ID:
<OS3PR01MB8319CB77A70EE45E7C5E17B48A6CA@OS3PR01MB8319.jpnprd01.prod.outlook.com>
Date: Wed, 4 Jun 2025 14:36:43 +0000
From: Chris Brandt <Chris.Brandt@...esas.com>
To: Hugo Villeneuve <hugo@...ovil.com>
CC: Biju Das <biju.das.jz@...renesas.com>, "maarten.lankhorst@...ux.intel.com"
<maarten.lankhorst@...ux.intel.com>, "mripard@...nel.org"
<mripard@...nel.org>, "tzimmermann@...e.de" <tzimmermann@...e.de>,
"airlied@...il.com" <airlied@...il.com>, "simona@...ll.ch" <simona@...ll.ch>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Hugo
Villeneuve <hvilleneuve@...onoff.com>
Subject: RE: [PATCH v3 2/2] drm: renesas: rz-du: Set DCS maximum return packet
size
Hi Hugo,
> Also, by default, most panels are configured to send a maximum of 1 byte, so it is not absolutely required by default and not really a bug.
Thanks. I found that I needed to call mipi_dsi_set_maximum_return_packet_size() first in my panel driver, then I could receive multiple bytes.
Chris
-----Original Message-----
From: Hugo Villeneuve <hugo@...ovil.com>
Sent: Wednesday, June 4, 2025 9:35 AM
To: Chris Brandt <Chris.Brandt@...esas.com>
Cc: Biju Das <biju.das.jz@...renesas.com>; maarten.lankhorst@...ux.intel.com; mripard@...nel.org; tzimmermann@...e.de; airlied@...il.com; simona@...ll.ch; dri-devel@...ts.freedesktop.org; linux-renesas-soc@...r.kernel.org; linux-kernel@...r.kernel.org; Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: Re: [PATCH v3 2/2] drm: renesas: rz-du: Set DCS maximum return packet size
On Wed, 4 Jun 2025 11:54:28 +0000
Chris Brandt <Chris.Brandt@...esas.com> wrote:
Hi Chris,
> Hi Hugo,
>
> I'm fine with the code, but maybe it should go in a different location.
>
> Since it's a register setup, it should probably go in rzg2l_mipi_dsi_startup() with the others.
It makes sense, I will move it there.
> Additionally, since it is required to make
> rzg2l_mipi_dsi_host_transfer() operate properly, my suggestion is to add this to your previous patch instead of making it separate.
> Otherwise, it's like you are submitting one patch with a known bug, then immediately fixing it with a second patch.
I made it a separate patch to clearly show why this is needed, because it took me a lot of time to figure this out, and I didn't want that knowledge to be lost :)
Also, by default, most panels are configured to send a maximum of 1 byte, so it is not absolutely required by default and not really a bug.
But sure I can merge it, anyway my comment will clearly indicate why it is needed.
> This also would prevent the merge conflict with my patch that also modifies rzg2l_mipi_dsi_atomic_enable().
Ok.
Hugo.
> Chris
>
>
> -----Original Message-----
> From: Hugo Villeneuve <hugo@...ovil.com>
> Sent: Thursday, May 22, 2025 10:39 AM
> To: Biju Das <biju.das.jz@...renesas.com>;
> maarten.lankhorst@...ux.intel.com; mripard@...nel.org;
> tzimmermann@...e.de; airlied@...il.com; simona@...ll.ch
> Cc: dri-devel@...ts.freedesktop.org;
> linux-renesas-soc@...r.kernel.org; linux-kernel@...r.kernel.org;
> hugo@...ovil.com; Hugo Villeneuve <hvilleneuve@...onoff.com>; Chris
> Brandt <Chris.Brandt@...esas.com>
> Subject: [PATCH v3 2/2] drm: renesas: rz-du: Set DCS maximum return
> packet size
>
> From: Hugo Villeneuve <hvilleneuve@...onoff.com>
>
> The default value of 1 will result in long read commands payload not being saved to memory.
>
> Fix by setting this value to the DMA buffer size.
>
> Cc: Biju Das <biju.das.jz@...renesas.com>
> Cc: Chris Brandt <chris.brandt@...esas.com>
> Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> ---
> drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c | 10 ++++++++++
> drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi_regs.h | 4 ++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> index a048d473db00b..745aae63af9d8 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> @@ -549,6 +549,7 @@ static void rzg2l_mipi_dsi_atomic_enable(struct drm_bridge *bridge,
> const struct drm_display_mode *mode;
> struct drm_connector *connector;
> struct drm_crtc *crtc;
> + u32 value;
> int ret;
>
> connector = drm_atomic_get_new_connector_for_encoder(state,
> bridge->encoder); @@ -561,6 +562,15 @@ static void
> rzg2l_mipi_dsi_atomic_enable(struct drm_bridge *bridge,
>
> rzg2l_mipi_dsi_set_display_timing(dsi, mode);
>
> + /*
> + * The default value of 1 will result in long read commands payload
> + * not being saved to memory. Set to the DMA buffer size.
> + */
> + value = rzg2l_mipi_dsi_link_read(dsi, DSISETR);
> + value &= ~DSISETR_MRPSZ;
> + value |= FIELD_PREP(DSISETR_MRPSZ, RZG2L_DCS_BUF_SIZE);
> + rzg2l_mipi_dsi_link_write(dsi, DSISETR, value);
> +
> ret = rzg2l_mipi_dsi_start_hs_clock(dsi);
> if (ret < 0)
> goto err_stop;
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi_regs.h
> b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi_regs.h
> index 0e432b04188d0..26d8a37ee6351 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi_regs.h
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi_regs.h
> @@ -81,6 +81,10 @@
> #define RSTSR_SWRSTLP (1 << 1)
> #define RSTSR_SWRSTHS (1 << 0)
>
> +/* DSI Set Register */
> +#define DSISETR 0x120
> +#define DSISETR_MRPSZ GENMASK(15, 0)
> +
> /* Rx Result Save Slot 0 Register */
> #define RXRSS0R 0x240
> #define RXRSS0R_RXPKTDFAIL BIT(28)
> --
> 2.39.5
>
>
--
Hugo Villeneuve
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