On Thu, 07 Apr 2022, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote:
> On Wed, 06 Apr 2022, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
>> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>>
>> Modern VBTs no longer contain the LFP data table pointers
>> block (41). We are expecting to have one in order to be able
>> to parse the LFP data block (42), so let's make one up.
>>
>> Since the fp_timing table has variable size we must somehow
>> determine its size. Rather than just hardcode it we look for
>> the terminator bytes (0xffff) to figure out where each table
>> entry starts. dvo_timing, panel_pnp_id, and panel_name are
>> expected to have fixed size.
>>
>> This has been observed on various machines, eg. TGL with BDB
>> version 240, CML with BDB version 231, etc. The most recent
>> VBT I've observed that still had block 41 had BDB version
>> 228. So presumably the cutoff (if an exact cutoff even exists)
>> is somewhere around BDB version 229-231.
>>
>> v2: kfree the thing we allocated, not the thing+3 bytes
>> v3: Do the debugprint only if we found the LFP data block
>>
>> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/display/intel_bios.c | 136 +++++++++++++++++++++-
>> 1 file changed, 135 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
>> index 8b118c54314d..d32091dad1b0 100644
>> --- a/drivers/gpu/drm/i915/display/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
>> @@ -310,16 +310,146 @@ static bool fixup_lfp_data_ptrs(const void *bdb, void *ptrs_block)
>> return validate_lfp_data_ptrs(bdb, ptrs);
>> }
>>
>> +static const void *find_fp_timing_terminator(const u8 *data, int size)
>> +{
>> + int i;
>> +
>> + if (!data)
>> + return NULL;
>> +
>> + for (i = 0; i < size - 1; i++) {
>> + if (data[i] == 0xff && data[i+1] == 0xff)
>> + return &data[i];
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> +static int make_lfp_data_ptr(struct lvds_lfp_data_ptr_table *table,
>> + int table_size, int total_size)
>> +{
>> + if (total_size < table_size)
>> + return total_size;
>> +
>> + table->table_size = table_size;
>> + table->offset = total_size - table_size;
>> +
>> + return total_size - table_size;
>> +}
>> +
>> +static void next_lfp_data_ptr(struct lvds_lfp_data_ptr_table *next,
>> + const struct lvds_lfp_data_ptr_table *prev,
>> + int size)
>> +{
>> + next->table_size = prev->table_size;
>> + next->offset = prev->offset + size;
>> +}
>> +
>> +static void *generate_lfp_data_ptrs(struct drm_i915_private *i915,
>> + const void *bdb)
>> +{
>> + int i, size, table_size, block_size, offset;
>> + const void *t0, *t1, *block;
>> + struct bdb_lvds_lfp_data_ptrs *ptrs;
>> + void *ptrs_block;
>> +
>> + block = find_raw_section(bdb, BDB_LVDS_LFP_DATA);
>> + if (!block)
>> + return NULL;
>> +
>> + drm_dbg_kms(&i915->drm, "Generating LFP data table pointers\n");
>> +
>> + block_size = get_blocksize(block);
>> +
>> + size = block_size;
>> + t0 = find_fp_timing_terminator(block, size);
>> +
>> + size -= t0 - block - 2;
>> + t1 = find_fp_timing_terminator(t0 + 2, size);
>
> Need to NULL check t0 before using it.
>
> I'll still keep trying to wrap my head around the below stuff.
I guess I'll try again tomorrow with fresh eyes, but I have a hard time
following what's going on here. x_X
BR,
Jani.
>
>> +
>> + if (!t0 || !t1)
>> + return NULL;
>> +
>> + size = t1 - t0;
>> + if (size * 16 > block_size)
>> + return NULL;
>> +
>> + ptrs_block = kzalloc(sizeof(*ptrs) + 3, GFP_KERNEL);
>> + if (!ptrs_block)
>> + return NULL;
>> +
>> + *(u8 *)(ptrs_block + 0) = BDB_LVDS_LFP_DATA_PTRS;
>> + *(u16 *)(ptrs_block + 1) = sizeof(*ptrs);
>> + ptrs = ptrs_block + 3;
>> +
>> + table_size = sizeof(struct lvds_pnp_id);
>> + size = make_lfp_data_ptr(&ptrs->ptr[0].panel_pnp_id, table_size, size);
>> +
>> + table_size = sizeof(struct lvds_dvo_timing);
>> + size = make_lfp_data_ptr(&ptrs->ptr[0].dvo_timing, table_size, size);
>> +
>> + table_size = t0 - block + 2;
>> + size = make_lfp_data_ptr(&ptrs->ptr[0].fp_timing, table_size, size);
>> +
>> + if (ptrs->ptr[0].fp_timing.table_size)
>> + ptrs->lvds_entries++;
>> + if (ptrs->ptr[0].dvo_timing.table_size)
>> + ptrs->lvds_entries++;
>> + if (ptrs->ptr[0].panel_pnp_id.table_size)
>> + ptrs->lvds_entries++;
>> +
>> + if (size != 0 || ptrs->lvds_entries != 3) {
>> + kfree(ptrs);
>> + return NULL;
>> + }
>> +
>> + size = t1 - t0;
>> + for (i = 1; i < 16; i++) {
>> + next_lfp_data_ptr(&ptrs->ptr[i].fp_timing, &ptrs->ptr[i-1].fp_timing, size);
>> + next_lfp_data_ptr(&ptrs->ptr[i].dvo_timing, &ptrs->ptr[i-1].dvo_timing, size);
>> + next_lfp_data_ptr(&ptrs->ptr[i].panel_pnp_id, &ptrs->ptr[i-1].panel_pnp_id, size);
>> + }
>> +
>> + size = t1 - t0;
>> + table_size = sizeof(struct lvds_lfp_panel_name);
>> +
>> + if (16 * (size + table_size) <= block_size) {
>> + ptrs->panel_name.table_size = table_size;
>> + ptrs->panel_name.offset = size * 16;
>> + }
>> +
>> + offset = block - bdb;
>> +
>> + for (i = 0; i < 16; i++) {
>> + ptrs->ptr[i].fp_timing.offset += offset;
>> + ptrs->ptr[i].dvo_timing.offset += offset;
>> + ptrs->ptr[i].panel_pnp_id.offset += offset;
>> + }
>> +
>> + if (ptrs->panel_name.table_size)
>> + ptrs->panel_name.offset += offset;
>> +
>> + return ptrs_block;
>> +}
>> +
>> static void
>> init_bdb_block(struct drm_i915_private *i915,
>> const void *bdb, enum bdb_block_id section_id,
>> size_t min_size)
>> {
>> struct bdb_block_entry *entry;
>> + void *temp_block = NULL;
>> const void *block;
>> size_t block_size;
>>
>> block = find_raw_section(bdb, section_id);
>> +
>> + /* Modern VBTs lack the LFP data table pointers block, make one up */
>> + if (!block && section_id == BDB_LVDS_LFP_DATA_PTRS) {
>> + temp_block = generate_lfp_data_ptrs(i915, bdb);
>> + if (temp_block)
>> + block = temp_block + 3;
>> + }
>> if (!block)
>> return;
>>
>> @@ -330,12 +460,16 @@ init_bdb_block(struct drm_i915_private *i915,
>>
>> entry = kzalloc(struct_size(entry, data, max(min_size, block_size) + 3),
>> GFP_KERNEL);
>> - if (!entry)
>> + if (!entry) {
>> + kfree(temp_block);
>> return;
>> + }
>>
>> entry->section_id = section_id;
>> memcpy(entry->data, block - 3, block_size + 3);
>>
>> + kfree(temp_block);
>> +
>> drm_dbg_kms(&i915->drm, "Found BDB block %d (size %zu, min size %zu)\n",
>> section_id, block_size, min_size);
--
Jani Nikula, Intel Open Source Graphics Center
