drm/amd/display: Enforce DPCD Address ranges

[WHY]
Some DPCD addresses, notably LTTPR Capability registers, are expected to
be read all together in a single DPCD transaction. Rather than force callers to
read registers they don't need, we want to quietly extend the addresses
read, and only return back the values the caller asked for.
This does not affect DPCD writes.

[HOW]
Create an additional layer above AUX to perform 'checked' DPCD
transactions.
Iterate through an array of DPCD address ranges that are marked as being
contiguous. If a requested read falls within one of those ranges, extend
the read to include the entire range.
After DPCD has been queried, copy the requested bytes into the caller's
data buffer, and deallocate all resources used.

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/Makefile

@@ -60,7 +60,7 @@ include $(AMD_DC)
 
 DISPLAY_CORE = dc.o  dc_stat.o dc_link.o dc_resource.o dc_hw_sequencer.o dc_sink.o \
 dc_surface.o dc_link_hwss.o dc_link_dp.o dc_link_ddc.o dc_debug.o dc_stream.o \
-dc_link_enc_cfg.o
+dc_link_enc_cfg.o dc_link_dpcd.o
 
 ifdef CONFIG_DRM_AMD_DC_DCN
 DISPLAY_CORE += dc_vm_helper.o

drivers/gpu/drm/amd/display/dc/core/dc_link.c

@@ -49,6 +49,7 @@
 #include "dmub/dmub_srv.h"
 #include "inc/hw/panel_cntl.h"
 #include "inc/link_enc_cfg.h"
+#include "inc/link_dpcd.h"
 
 #define DC_LOGGER_INIT(logger)
 

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -25,6 +25,8 @@ static const uint8_t DP_VGA_LVDS_CONVERTER_ID_3[] = "dnomlA";
 	link->ctx->logger
 #define DC_TRACE_LEVEL_MESSAGE(...) /* do nothing */
 
+#include "link_dpcd.h"
+
 	/* maximum pre emphasis level allowed for each voltage swing level*/
 	static const enum dc_pre_emphasis
 	voltage_swing_to_pre_emphasis[] = { PRE_EMPHASIS_LEVEL3,

drivers/gpu/drm/amd/display/dc/core/dc_link_dpcd.c

@@ -0,0 +1,135 @@
+#include <inc/core_status.h>
+#include <dc_link.h>
+#include <inc/link_hwss.h>
+#include <inc/link_dpcd.h>
+#include "drm/drm_dp_helper.h"
+#include <dc_dp_types.h>
+#include "dm_helpers.h"
+
+#define END_ADDRESS(start, size) (start + size - 1)
+#define ADDRESS_RANGE_SIZE(start, end) (end - start + 1)
+struct dpcd_address_range {
+	uint32_t start;
+	uint32_t end;
+};
+
+static enum dc_status internal_link_read_dpcd(
+	struct dc_link *link,
+	uint32_t address,
+	uint8_t *data,
+	uint32_t size)
+{
+	if (!link->aux_access_disabled &&
+			!dm_helpers_dp_read_dpcd(link->ctx,
+			link, address, data, size)) {
+		return DC_ERROR_UNEXPECTED;
+	}
+
+	return DC_OK;
+}
+
+static enum dc_status internal_link_write_dpcd(
+	struct dc_link *link,
+	uint32_t address,
+	const uint8_t *data,
+	uint32_t size)
+{
+	if (!link->aux_access_disabled &&
+			!dm_helpers_dp_write_dpcd(link->ctx,
+			link, address, data, size)) {
+		return DC_ERROR_UNEXPECTED;
+	}
+
+	return DC_OK;
+}
+
+/*
+ * Ranges of DPCD addresses that must be read in a single transaction
+ * XXX: Do not allow any two address ranges in this array to overlap
+ */
+static const struct dpcd_address_range mandatory_dpcd_blocks[] = {
+	{ DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV, DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT }};
+
+/*
+ * extend addresses to read all mandatory blocks together
+ */
+static void dpcd_extend_address_range(
+		const uint32_t in_address,
+		uint8_t * const in_data,
+		const uint32_t in_size,
+		uint32_t *out_address,
+		uint8_t **out_data,
+		uint32_t *out_size)
+{
+	const uint32_t end_address = END_ADDRESS(in_address, in_size);
+	const struct dpcd_address_range *addr_range;
+	struct dpcd_address_range new_addr_range;
+	uint32_t i;
+
+	new_addr_range.start = in_address;
+	new_addr_range.end = end_address;
+	for (i = 0; i < ARRAY_SIZE(mandatory_dpcd_blocks); i++) {
+		addr_range = &mandatory_dpcd_blocks[i];
+		if (addr_range->start <= in_address && addr_range->end >= in_address)
+			new_addr_range.start = addr_range->start;
+
+		if (addr_range->start <= end_address && addr_range->end >= end_address)
+			new_addr_range.end = addr_range->end;
+	}
+	*out_address = in_address;
+	*out_size = in_size;
+	*out_data = in_data;
+	if (new_addr_range.start != in_address || new_addr_range.end != end_address) {
+		*out_address = new_addr_range.start;
+		*out_size = ADDRESS_RANGE_SIZE(new_addr_range.start, new_addr_range.end);
+		*out_data = kzalloc(*out_size * sizeof(**out_data), GFP_KERNEL);
+	}
+}
+
+/*
+ * Reduce the AUX reply down to the values the caller requested
+ */
+static void dpcd_reduce_address_range(
+		const uint32_t extended_address,
+		uint8_t * const extended_data,
+		const uint32_t extended_size,
+		const uint32_t reduced_address,
+		uint8_t * const reduced_data,
+		const uint32_t reduced_size)
+{
+	const uint32_t reduced_end_address = END_ADDRESS(reduced_address, reduced_size);
+	const uint32_t extended_end_address = END_ADDRESS(reduced_address, extended_size);
+	const uint32_t offset = reduced_address - extended_address;
+
+	if (extended_end_address == reduced_end_address && extended_address == reduced_address)
+		return; /* extended and reduced address ranges point to the same data */
+
+	memcpy(&extended_data[offset], reduced_data, reduced_size);
+	kfree(extended_data);
+}
+
+enum dc_status core_link_read_dpcd(
+	struct dc_link *link,
+	uint32_t address,
+	uint8_t *data,
+	uint32_t size)
+{
+	uint32_t extended_address;
+	uint8_t *extended_data;
+	uint32_t extended_size;
+	enum dc_status status;
+
+	dpcd_extend_address_range(address, data, size, &extended_address, &extended_data, &extended_size);
+	status = internal_link_read_dpcd(link, extended_address, extended_data, extended_size);
+	dpcd_reduce_address_range(extended_address, extended_data, extended_size, address, data, size);
+	return status;
+}
+
+enum dc_status core_link_write_dpcd(
+	struct dc_link *link,
+	uint32_t address,
+	const uint8_t *data,
+	uint32_t size)
+{
+	return internal_link_write_dpcd(link, address, data, size);
+}

drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c

@@ -16,6 +16,7 @@
 #include "resource.h"
 #include "link_enc_cfg.h"
 #include "clk_mgr.h"
+#include "inc/link_dpcd.h"
 
 static uint8_t convert_to_count(uint8_t lttpr_repeater_count)
 {
@@ -47,36 +48,6 @@ static inline bool is_immediate_downstream(struct dc_link *link, uint32_t offset
 	return (convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt) == offset);
 }
 
-enum dc_status core_link_read_dpcd(
-	struct dc_link *link,
-	uint32_t address,
-	uint8_t *data,
-	uint32_t size)
-{
-	if (!link->aux_access_disabled &&
-			!dm_helpers_dp_read_dpcd(link->ctx,
-			link, address, data, size)) {
-		return DC_ERROR_UNEXPECTED;
-	}
-
-	return DC_OK;
-}
-
-enum dc_status core_link_write_dpcd(
-	struct dc_link *link,
-	uint32_t address,
-	const uint8_t *data,
-	uint32_t size)
-{
-	if (!link->aux_access_disabled &&
-			!dm_helpers_dp_write_dpcd(link->ctx,
-			link, address, data, size)) {
-		return DC_ERROR_UNEXPECTED;
-	}
-
-	return DC_OK;
-}
-
 void dp_receiver_power_ctrl(struct dc_link *link, bool on)
 {
 	uint8_t state;

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c

@@ -55,6 +55,7 @@
 #include "dc_trace.h"
 #include "dce/dmub_outbox.h"
 #include "inc/dc_link_dp.h"
+#include "inc/link_dpcd.h"
 
 #define DC_LOGGER_INIT(logger)
 

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c

@@ -49,6 +49,7 @@
 #include "link_hwss.h"
 #include "dpcd_defs.h"
 #include "inc/dc_link_dp.h"
+#include "inc/link_dpcd.h"
 
 
 

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_hwseq.c

@@ -46,6 +46,7 @@
 #include "dpcd_defs.h"
 #include "dce/dmub_outbox.h"
 #include "dc_link_dp.h"
+#include "inc/link_dpcd.h"
 
 #define DC_LOGGER_INIT(logger)
 

drivers/gpu/drm/amd/display/dc/hdcp/hdcp_msg.c

@@ -33,6 +33,7 @@
 #include "core_types.h"
 #include "dc_link_ddc.h"
 #include "link_hwss.h"
+#include "inc/link_dpcd.h"
 
 #define DC_LOGGER \
 	link->ctx->logger

drivers/gpu/drm/amd/display/dc/inc/link_dpcd.h

@@ -0,0 +1,18 @@
+#ifndef __LINK_DPCD_H__
+#define __LINK_DPCD_H__
+#include <inc/core_status.h>
+#include <dc_link.h>
+#include <inc/link_hwss.h>
+
+enum dc_status core_link_read_dpcd(
+		struct dc_link *link,
+		uint32_t address,
+		uint8_t *data,
+		uint32_t size);
+
+enum dc_status core_link_write_dpcd(
+		struct dc_link *link,
+		uint32_t address,
+		const uint8_t *data,
+		uint32_t size);
+#endif

drivers/gpu/drm/amd/display/dc/inc/link_hwss.h

@@ -26,20 +26,6 @@
 #ifndef __DC_LINK_HWSS_H__
 #define __DC_LINK_HWSS_H__
 
-#include "inc/core_status.h"
-
-enum dc_status core_link_read_dpcd(
-	struct dc_link *link,
-	uint32_t address,
-	uint8_t *data,
-	uint32_t size);
-
-enum dc_status core_link_write_dpcd(
-	struct dc_link *link,
-	uint32_t address,
-	const uint8_t *data,
-	uint32_t size);
-
 struct gpio *get_hpd_gpio(struct dc_bios *dcb,
 		struct graphics_object_id link_id,
 		struct gpio_service *gpio_service);