On Tue, Feb 16, 2021 at 10:15 AM Jae Hyun Yoo <jae.hyun.yoo@xxxxxxxxxxxxxxx> wrote: > > This driver uses byte mode that makes lots of interrupt calls > so it's not good for performance. Also, it makes the driver very > timing sensitive. To improve performance of the driver, this commit > modifies I2C node to support buffer mode which uses I2C SRAM buffer > instead of using a single byte buffer. > > AST2400: > It has 2 KBytes (256 Bytes x 8 pages) of I2C SRAM buffer pool from > 0x1e78a800 to 0x1e78afff that can be used for all busses with > buffer pool manipulation. To simplify implementation for supporting > both AST2400 and AST2500, it assigns each 128 Bytes per bus without > using buffer pool manipulation so total 1792 Bytes of I2C SRAM > buffer will be used. > > AST2500: > It has 16 Bytes of individual I2C SRAM buffer per each bus and its > range is from 0x1e78a200 to 0x1e78a2df, so it doesn't have 'buffer > page selection' bit field in the Function control register, and > neither 'base address pointer' bit field in the Pool buffer control > register it has. To simplify implementation for supporting both > AST2400 and AST2500, it writes zeros on those register bit fields > but it's okay because it does nothing in AST2500. > > AST2600: > It has 32 Bytes of individual I2C SRAM buffer per each bus and its > range is from 0x1e78ac00 to 0x1e78adff. Works just like AST2500 > does. > > See Documentation/devicetree/bindings/i2c/i2c-aspeed.txt for > enabling buffer mode details. > > Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@xxxxxxxxxxxxxxx> > Reviewed-by: Cédric Le Goater <clg@xxxxxxxx> Reviewed-by: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
