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Unverified Commit c51756d5 authored by Kees Cook's avatar Kees Cook Committed by Maxime Ripard
Browse files

drm/sun4i: Remove VLA usage 

In the quest to remove all stack VLA usage from the kernel[1], this
switches to using a kmalloc allocation and moves all the size calculations
to the start to do an allocation. If an upper bounds on the mode timing
calculations could be determined, a fixed stack size could be used instead.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com



Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarMaxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180629184740.GA37415@beast
parent 968d72e6

drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c

+64 −43
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/pm_runtime.h>

#include <linux/regmap.h>

#include <linux/reset.h>

#include <linux/slab.h>



#include <linux/phy/phy.h>
@@ -247,10 +248,8 @@ static u16 sun6i_dsi_crc_compute(u8 const *buffer, size_t len) 
	return crc_ccitt(0xffff, buffer, len);

}



static u16 sun6i_dsi_crc_repeat_compute(u8 pd, size_t len)

static u16 sun6i_dsi_crc_repeat(u8 pd, u8 *buffer, size_t len)

{

	u8 buffer[len];



	memset(buffer, pd, len);



	return sun6i_dsi_crc_compute(buffer, len);
@@ -274,11 +273,11 @@ static u32 sun6i_dsi_build_blk0_pkt(u8 vc, u16 wc) 
					wc & 0xff, wc >> 8);

}



static u32 sun6i_dsi_build_blk1_pkt(u16 pd, size_t len)

static u32 sun6i_dsi_build_blk1_pkt(u16 pd, u8 *buffer, size_t len)

{

	u32 val = SUN6I_DSI_BLK_PD(pd);



	return val | SUN6I_DSI_BLK_PF(sun6i_dsi_crc_repeat_compute(pd, len));

	return val | SUN6I_DSI_BLK_PF(sun6i_dsi_crc_repeat(pd, buffer, len));

}



static void sun6i_dsi_inst_abort(struct sun6i_dsi *dsi)
@@ -452,6 +451,54 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi, 
	struct mipi_dsi_device *device = dsi->device;

	unsigned int Bpp = mipi_dsi_pixel_format_to_bpp(device->format) / 8;

	u16 hbp, hfp, hsa, hblk, vblk;

	size_t bytes;

	u8 *buffer;



	/* Do all timing calculations up front to allocate buffer space */



	/*

	 * A sync period is composed of a blanking packet (4 bytes +

	 * payload + 2 bytes) and a sync event packet (4 bytes). Its

	 * minimal size is therefore 10 bytes

	 */

#define HSA_PACKET_OVERHEAD	10

	hsa = max((unsigned int)HSA_PACKET_OVERHEAD,

		  (mode->hsync_end - mode->hsync_start) * Bpp - HSA_PACKET_OVERHEAD);



	/*

	 * The backporch is set using a blanking packet (4 bytes +

	 * payload + 2 bytes). Its minimal size is therefore 6 bytes

	 */

#define HBP_PACKET_OVERHEAD	6

	hbp = max((unsigned int)HBP_PACKET_OVERHEAD,

		  (mode->hsync_start - mode->hdisplay) * Bpp - HBP_PACKET_OVERHEAD);



	/*

	 * The frontporch is set using a blanking packet (4 bytes +

	 * payload + 2 bytes). Its minimal size is therefore 6 bytes

	 */

#define HFP_PACKET_OVERHEAD	6

	hfp = max((unsigned int)HFP_PACKET_OVERHEAD,

		  (mode->htotal - mode->hsync_end) * Bpp - HFP_PACKET_OVERHEAD);



	/*

	 * hblk seems to be the line + porches length.

	 */

	hblk = mode->htotal * Bpp - hsa;



	/*

	 * And I'm not entirely sure what vblk is about. The driver in

	 * Allwinner BSP is using a rather convoluted calculation

	 * there only for 4 lanes. However, using 0 (the !4 lanes

	 * case) even with a 4 lanes screen seems to work...

	 */

	vblk = 0;



	/* How many bytes do we need to send all payloads? */

	bytes = max_t(size_t, max(max(hfp, hblk), max(hsa, hbp)), vblk);

	buffer = kmalloc(bytes, GFP_KERNEL);

	if (WARN_ON(!buffer))

		return;



	regmap_write(dsi->regs, SUN6I_DSI_BASIC_CTL_REG, 0);
@@ -485,63 +532,37 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi, 
		     SUN6I_DSI_BASIC_SIZE1_VACT(mode->vdisplay) |

		     SUN6I_DSI_BASIC_SIZE1_VT(mode->vtotal));



	/*

	 * A sync period is composed of a blanking packet (4 bytes +

	 * payload + 2 bytes) and a sync event packet (4 bytes). Its

	 * minimal size is therefore 10 bytes

	 */

#define HSA_PACKET_OVERHEAD	10

	hsa = max((unsigned int)HSA_PACKET_OVERHEAD,

		  (mode->hsync_end - mode->hsync_start) * Bpp - HSA_PACKET_OVERHEAD);

	/* sync */

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HSA0_REG,

		     sun6i_dsi_build_blk0_pkt(device->channel, hsa));

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HSA1_REG,

		     sun6i_dsi_build_blk1_pkt(0, hsa));

		     sun6i_dsi_build_blk1_pkt(0, buffer, hsa));



	/*

	 * The backporch is set using a blanking packet (4 bytes +

	 * payload + 2 bytes). Its minimal size is therefore 6 bytes

	 */

#define HBP_PACKET_OVERHEAD	6

	hbp = max((unsigned int)HBP_PACKET_OVERHEAD,

		  (mode->hsync_start - mode->hdisplay) * Bpp - HBP_PACKET_OVERHEAD);

	/* backporch */

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HBP0_REG,

		     sun6i_dsi_build_blk0_pkt(device->channel, hbp));

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HBP1_REG,

		     sun6i_dsi_build_blk1_pkt(0, hbp));

		     sun6i_dsi_build_blk1_pkt(0, buffer, hbp));



	/*

	 * The frontporch is set using a blanking packet (4 bytes +

	 * payload + 2 bytes). Its minimal size is therefore 6 bytes

	 */

#define HFP_PACKET_OVERHEAD	6

	hfp = max((unsigned int)HFP_PACKET_OVERHEAD,

		  (mode->htotal - mode->hsync_end) * Bpp - HFP_PACKET_OVERHEAD);

	/* frontporch */

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HFP0_REG,

		     sun6i_dsi_build_blk0_pkt(device->channel, hfp));

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HFP1_REG,

		     sun6i_dsi_build_blk1_pkt(0, hfp));

		     sun6i_dsi_build_blk1_pkt(0, buffer, hfp));



	/*

	 * hblk seems to be the line + porches length.

	 */

	hblk = mode->htotal * Bpp - hsa;

	/* hblk */

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HBLK0_REG,

		     sun6i_dsi_build_blk0_pkt(device->channel, hblk));

	regmap_write(dsi->regs, SUN6I_DSI_BLK_HBLK1_REG,

		     sun6i_dsi_build_blk1_pkt(0, hblk));

		     sun6i_dsi_build_blk1_pkt(0, buffer, hblk));



	/*

	 * And I'm not entirely sure what vblk is about. The driver in

	 * Allwinner BSP is using a rather convoluted calculation

	 * there only for 4 lanes. However, using 0 (the !4 lanes

	 * case) even with a 4 lanes screen seems to work...

	 */

	vblk = 0;

	/* vblk */

	regmap_write(dsi->regs, SUN6I_DSI_BLK_VBLK0_REG,

		     sun6i_dsi_build_blk0_pkt(device->channel, vblk));

	regmap_write(dsi->regs, SUN6I_DSI_BLK_VBLK1_REG,

		     sun6i_dsi_build_blk1_pkt(0, vblk));

		     sun6i_dsi_build_blk1_pkt(0, buffer, vblk));



	kfree(buffer);

}



static int sun6i_dsi_start(struct sun6i_dsi *dsi,