Commits on May 22, 2024

1. drivers: irqsteer: adjust CHn_MASK index computation …

   For IRQ_STEER, lower CHn_MASK register indexes are used
   to mask higher interrupt IDs. For instance, in the case
   of i.MX8MP, the mapping is as follows:
   
   	CHn_MASK4 => masks interrupts [31:0]
   	CHn_MASK3 => masks interrupts [63:32]
   	CHn_MASK2 => masks interrupts [95:64]
   	CHn_MASK1 => masks interrupts [127:96]
   	CHn_MASK0 => masks interrupts [159:128]
   
   The `IRQSTEER_GetRegIndex()` function is used to fetch
   the CHn_MASK register index based on a given slice. The term
   "slice" is used to refer to an index of a CHn_MASK register in
   the set of CHn_MASK registers assigned to a certain master. Assuming
   the following partition scheme (i.MX8MP):
   
   	{ CHn_MASK4 } is assigned to MASTER0
   	{ CHn_MASK3, CHn_MASK2 } is assigned to MASTER1
   	{ CHn_MASK1, CHn_MASK0 } is assiged to MASTER2
   
   CHn_MASK3 would be at slice (index) 0, CHn_MASK2 would be at
   slice 1, CHn_MASK1 would be at slice 0 and so on.
   
   To compute the CHn_MASK register index found at a given slice,
   `IRQSTEER_GetRegIndex()` uses a base index, which is either
   the lowest or the highest CHn_MASK register index in a master's
   partition (for instance, for MASTER1 the higher would be 3 and
   the lowest would be 2).
   
   For IRQ_STEER instances with an uneven number of CHn_MASK registers
   the base is the lowest index, while in the case of instances with
   an even number of CHn_MASK registers it's exactly the opposite. This
   is an issue because the software using this function might expect
   the base to either be the lowest or the highest index ALL THE TIME
   (since this affects the order in which the CHn_MASK register indexes
   are returned).
   
   As such, fix this problem by making the base the highest CHn_MASK
   register index.
   
   Signed-off-by: Laurentiu Mihalcea <[email protected]>

   

   LaurentiuM1234 committed May 22, 2024
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