linux-kernel - Re: [PATCH] drm/bridge/synopsys: dsi: Add read feature

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Message-ID: <20180206015306.GA112054@ban.mtv.corp.google.com>
Date:   Mon, 5 Feb 2018 17:53:06 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Philippe Cornu <philippe.cornu@...com>
Cc:     Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Bhumika Goyal <bhumirks@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stubner <heiko@...ech.de>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org,
        Yannick Fertre <yannick.fertre@...com>,
        Vincent Abriou <vincent.abriou@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Lin Huang <hl@...k-chips.com>, mka@...omium.org
Subject: Re: [PATCH] drm/bridge/synopsys: dsi: Add read feature

Hi,

On Sun, Feb 04, 2018 at 10:31:04PM +0100, Philippe Cornu wrote:
> This patch adds the DCS/GENERIC DSI read feature.
> 
> Signed-off-by: Philippe Cornu <philippe.cornu@...com>
> ---
> Extra notes:
> DSI read tests have been performed with DCS & GENERIC, short & long
> commands, on two different panels.
> The maximum fifo size (32*32-bit = 128 bytes on stm32) has been
> verified too.

Seems OK to me, just comparing with work we've been borrowing from
Rockchip:

https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/863347

(And in fact, it looks much better than that.)

So FWIW:

Reviewed-by: Brian Norris <briannorris@...omium.org>

and thanks a bunch!

Brian

>  drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 58 +++++++++++++++++++++------
>  1 file changed, 45 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index e9422d05e897..65aeb3f78b48 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -397,18 +397,46 @@ static int dw_mipi_dsi_write(struct dw_mipi_dsi *dsi,
>  	return dw_mipi_dsi_gen_pkt_hdr_write(dsi, le32_to_cpu(word));
>  }
>  
> +static int dw_mipi_dsi_read(struct dw_mipi_dsi *dsi,
> +			    const struct mipi_dsi_msg *msg)
> +{
> +	int i, j, ret, len = msg->rx_len;
> +	u8 *buf = msg->rx_buf;
> +	u32 val;
> +
> +	/* Wait end of the read operation */
> +	ret = readl_poll_timeout(dsi->base + DSI_CMD_PKT_STATUS,
> +				 val, !(val & GEN_RD_CMD_BUSY),
> +				 1000, CMD_PKT_STATUS_TIMEOUT_US);
> +	if (ret) {
> +		dev_err(dsi->dev, "Timeout during read operation\n");
> +		return ret;
> +	}
> +
> +	for (i = 0; i < len; i += 4) {
> +		/* Read fifo must not be empty before all bytes are read */
> +		ret = readl_poll_timeout(dsi->base + DSI_CMD_PKT_STATUS,
> +					 val, !(val & GEN_PLD_R_EMPTY),
> +					 1000, CMD_PKT_STATUS_TIMEOUT_US);
> +		if (ret) {
> +			dev_err(dsi->dev, "Read payload FIFO is empty\n");
> +			return ret;
> +		}
> +
> +		val = dsi_read(dsi, DSI_GEN_PLD_DATA);
> +		for (j = 0; j < 4 && j + i < len; j++)
> +			buf[i + j] = val >> (8 * j);
> +	}
> +
> +	return ret;
> +}
> +
>  static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
>  					 const struct mipi_dsi_msg *msg)
>  {
>  	struct dw_mipi_dsi *dsi = host_to_dsi(host);
>  	struct mipi_dsi_packet packet;
> -	int ret;
> -
> -	if (msg->rx_buf || msg->rx_len) {
> -		/* TODO dw drv improvements: implement read feature */
> -		dev_warn(dsi->dev, "read operations not yet implemented\n");
> -		return -EINVAL;
> -	}
> +	int ret, nb_bytes;
>  
>  	ret = mipi_dsi_create_packet(&packet, msg);
>  	if (ret) {
> @@ -422,12 +450,16 @@ static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
>  	if (ret)
>  		return ret;
>  
> -	/*
> -	 * TODO Only transmitted size is returned as actual driver does
> -	 * not support dcs/generic reads. Please update return value when
> -	 * delivering the read feature.
> -	 */
> -	return packet.size;
> +	if (msg->rx_buf && msg->rx_len) {
> +		ret = dw_mipi_dsi_read(dsi, msg);
> +		if (ret)
> +			return ret;
> +		nb_bytes = msg->rx_len;
> +	} else {
> +		nb_bytes = packet.size;
> +	}
> +
> +	return nb_bytes;
>  }
>  
>  static const struct mipi_dsi_host_ops dw_mipi_dsi_host_ops = {
> -- 
> 2.15.1
>