linux-kernel - Re: [PATCH v3 3/5] drm/mipi-dbi: Make bits per word configurable for pixel transfers

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Date: Mon, 3 Jun 2024 23:32:18 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: noralf@...nnes.org
Cc: Neil Armstrong <neil.armstrong@...aro.org>, 
	Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg <sam@...nborg.org>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	David Lechner <david@...hnology.com>, dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Kamlesh Gurudasani <kamlesh.gurudasani@...il.com>, 
	Tommaso Merciai <tommaso.merciai@...rulasolutions.com>
Subject: Re: [PATCH v3 3/5] drm/mipi-dbi: Make bits per word configurable for
 pixel transfers

On Mon, Jun 03, 2024 at 01:21:34PM +0200, Noralf Trønnes via B4 Relay wrote:
> From: Noralf Trønnes <noralf@...nnes.org>
> 
> This prepares for supporting other pixel formats than RGB565.

Yes, the patch is pretty simple, however could you please expand the
commit message by describing write_memory_bpw introduction.

> 
> Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> ---
>  drivers/gpu/drm/drm_mipi_dbi.c | 14 ++++++++++----
>  include/drm/drm_mipi_dbi.h     |  5 +++++
>  2 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
> index fa8aba6dc81c..77f8a828d6e0 100644
> --- a/drivers/gpu/drm/drm_mipi_dbi.c
> +++ b/drivers/gpu/drm/drm_mipi_dbi.c
> @@ -1079,7 +1079,7 @@ static int mipi_dbi_typec1_command_read(struct mipi_dbi *dbi, u8 *cmd,
>  static int mipi_dbi_typec1_command(struct mipi_dbi *dbi, u8 *cmd,
>  				   u8 *parameters, size_t num)
>  {
> -	unsigned int bpw = (*cmd == MIPI_DCS_WRITE_MEMORY_START) ? 16 : 8;
> +	unsigned int bpw = 8;
>  	int ret;
>  
>  	if (mipi_dbi_command_is_read(dbi, *cmd))
> @@ -1091,6 +1091,9 @@ static int mipi_dbi_typec1_command(struct mipi_dbi *dbi, u8 *cmd,
>  	if (ret || !num)
>  		return ret;
>  
> +	if (*cmd == MIPI_DCS_WRITE_MEMORY_START)
> +		bpw = dbi->write_memory_bpw;
> +
>  	return mipi_dbi_spi1_transfer(dbi, 1, parameters, num, bpw);
>  }
>  
> @@ -1184,8 +1187,8 @@ static int mipi_dbi_typec3_command(struct mipi_dbi *dbi, u8 *cmd,
>  	if (ret || !num)
>  		return ret;
>  
> -	if (*cmd == MIPI_DCS_WRITE_MEMORY_START && !dbi->swap_bytes)
> -		bpw = 16;
> +	if (*cmd == MIPI_DCS_WRITE_MEMORY_START)
> +		bpw = dbi->write_memory_bpw;
>  
>  	spi_bus_lock(spi->controller);
>  	gpiod_set_value_cansleep(dbi->dc, 1);
> @@ -1256,12 +1259,15 @@ int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *dbi,
>  
>  	dbi->spi = spi;
>  	dbi->read_commands = mipi_dbi_dcs_read_commands;
> +	dbi->write_memory_bpw = 16;
>  
>  	if (dc) {
>  		dbi->command = mipi_dbi_typec3_command;
>  		dbi->dc = dc;
> -		if (!spi_is_bpw_supported(spi, 16))
> +		if (!spi_is_bpw_supported(spi, 16)) {
> +			dbi->write_memory_bpw = 8;
>  			dbi->swap_bytes = true;
> +		}
>  	} else {
>  		dbi->command = mipi_dbi_typec1_command;
>  		dbi->tx_buf9_len = SZ_16K;
> diff --git a/include/drm/drm_mipi_dbi.h b/include/drm/drm_mipi_dbi.h
> index e8e0f8d39f3a..b36596efdcc3 100644
> --- a/include/drm/drm_mipi_dbi.h
> +++ b/include/drm/drm_mipi_dbi.h
> @@ -56,6 +56,11 @@ struct mipi_dbi {
>  	 */
>  	struct spi_device *spi;
>  
> +	/**
> +	 * @write_memory_bpw: Bits per word used on a MIPI_DCS_WRITE_MEMORY_START transfer
> +	 */
> +	unsigned int write_memory_bpw;
> +
>  	/**
>  	 * @dc: Optional D/C gpio.
>  	 */
> 
> -- 
> 2.45.1
> 
> 

-- 
With best wishes
Dmitry