linux-kernel - RE: [PATCH v3 2/2] drm: renesas: rz-du: Set DCS maximum return packet size

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Message-ID:
 <OS3PR01MB83195CC101339CA1ECDCD6C78A6CA@OS3PR01MB8319.jpnprd01.prod.outlook.com>
Date: Wed, 4 Jun 2025 12:08:49 +0000
From: Chris Brandt <Chris.Brandt@...esas.com>
To: Hugo Villeneuve <hugo@...ovil.com>, 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>
CC: "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,

Sorry, one more thing....

> +	/*
> +	 * The default value of 1 will result in long read commands payload
> +	 * not being saved to memory. Set to the DMA buffer size.
> +	 */

The comment is a bit wordy.

You just need to say:

/* Set read buffer size */

Or...no comment at all. It's pretty obvious what the code is doing because you are writing
RZG2L_DCS_BUF_SIZE to a register.

Chris


-----Original Message-----
From: Chris Brandt 
Sent: Wednesday, June 4, 2025 7:54 AM
To: Hugo Villeneuve <hugo@...ovil.com>; 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 Villeneuve <hvilleneuve@...onoff.com>
Subject: RE: [PATCH v3 2/2] drm: renesas: rz-du: Set DCS maximum return packet size

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.

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.

This also would prevent the merge conflict with my patch that also modifies rzg2l_mipi_dsi_atomic_enable().

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