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[PATCH v2 11/26] drm/rockchip: dw-mipi-dsi: don't assume buffer is aligned

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  [PATCH v2 11/26] drm/rockchip: dw-mipi-dsi: don't assume buffer is aligned John Keeping <john@metanate.com> - 2017-01-21 17:40 +0100
    Re: [PATCH v2 11/26] drm/rockchip: dw-mipi-dsi: don't assume buffer  is aligned Chris Zhong <zyw@rock-chips.com> - 2017-01-22 09:20 +0100

#1564161 — [PATCH v2 11/26] drm/rockchip: dw-mipi-dsi: don't assume buffer is aligned

By dereferencing the MIPI command buffer as a u32* we rely on it being
correctly aligned on ARM, but this may not be the case.  Copy it into a
stack variable that will be correctly aligned.

Signed-off-by: John Keeping <john@metanate.com>
---
Unchanged in v2
---
 drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
index 03fc096fe1bd..ddbc037e7ced 100644
--- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
@@ -607,10 +607,10 @@ static int dw_mipi_dsi_dcs_short_write(struct dw_mipi_dsi *dsi,
 static int dw_mipi_dsi_dcs_long_write(struct dw_mipi_dsi *dsi,
 				      const struct mipi_dsi_msg *msg)
 {
-	const u32 *tx_buf = msg->tx_buf;
-	int len = msg->tx_len, pld_data_bytes = sizeof(*tx_buf), ret;
+	const u8 *tx_buf = msg->tx_buf;
+	int len = msg->tx_len, pld_data_bytes = sizeof(u32), ret;
 	u32 hdr_val = GEN_HDATA(msg->tx_len) | GEN_HTYPE(msg->type);
-	u32 remainder = 0;
+	u32 remainder;
 	u32 val;
 
 	if (msg->tx_len < 3) {
@@ -621,12 +621,14 @@ static int dw_mipi_dsi_dcs_long_write(struct dw_mipi_dsi *dsi,
 
 	while (DIV_ROUND_UP(len, pld_data_bytes)) {
 		if (len < pld_data_bytes) {
+			remainder = 0;
 			memcpy(&remainder, tx_buf, len);
 			dsi_write(dsi, DSI_GEN_PLD_DATA, remainder);
 			len = 0;
 		} else {
-			dsi_write(dsi, DSI_GEN_PLD_DATA, *tx_buf);
-			tx_buf++;
+			memcpy(&remainder, tx_buf, pld_data_bytes);
+			dsi_write(dsi, DSI_GEN_PLD_DATA, remainder);
+			tx_buf += pld_data_bytes;
 			len -= pld_data_bytes;
 		}
 
-- 
2.11.0.197.gb556de5.dirty

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#1564327 — Re: [PATCH v2 11/26] drm/rockchip: dw-mipi-dsi: don't assume buffer is aligned

Hi John

Reviewed-by: Chris Zhong <zyw@rock-chips.com>


On 01/22/2017 12:31 AM, John Keeping wrote:
> By dereferencing the MIPI command buffer as a u32* we rely on it being
> correctly aligned on ARM, but this may not be the case.  Copy it into a
> stack variable that will be correctly aligned.
>
> Signed-off-by: John Keeping <john@metanate.com>
> ---
> Unchanged in v2
> ---
>   drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> index 03fc096fe1bd..ddbc037e7ced 100644
> --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi.c
> @@ -607,10 +607,10 @@ static int dw_mipi_dsi_dcs_short_write(struct dw_mipi_dsi *dsi,
>   static int dw_mipi_dsi_dcs_long_write(struct dw_mipi_dsi *dsi,
>   				      const struct mipi_dsi_msg *msg)
>   {
> -	const u32 *tx_buf = msg->tx_buf;
> -	int len = msg->tx_len, pld_data_bytes = sizeof(*tx_buf), ret;
> +	const u8 *tx_buf = msg->tx_buf;
> +	int len = msg->tx_len, pld_data_bytes = sizeof(u32), ret;
>   	u32 hdr_val = GEN_HDATA(msg->tx_len) | GEN_HTYPE(msg->type);
> -	u32 remainder = 0;
> +	u32 remainder;
>   	u32 val;
>   
>   	if (msg->tx_len < 3) {
> @@ -621,12 +621,14 @@ static int dw_mipi_dsi_dcs_long_write(struct dw_mipi_dsi *dsi,
>   
>   	while (DIV_ROUND_UP(len, pld_data_bytes)) {
>   		if (len < pld_data_bytes) {
> +			remainder = 0;
>   			memcpy(&remainder, tx_buf, len);
>   			dsi_write(dsi, DSI_GEN_PLD_DATA, remainder);
>   			len = 0;
>   		} else {
> -			dsi_write(dsi, DSI_GEN_PLD_DATA, *tx_buf);
> -			tx_buf++;
> +			memcpy(&remainder, tx_buf, pld_data_bytes);
> +			dsi_write(dsi, DSI_GEN_PLD_DATA, remainder);
> +			tx_buf += pld_data_bytes;
>   			len -= pld_data_bytes;
>   		}
>   

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