From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Anderson Date: Thu, 4 Feb 2021 23:43:36 -0500 Subject: [RFC PATCH 00/13] spi: dw: Add support for XIP mode In-Reply-To: <20210205043924.149504-1-seanga2@gmail.com> References: <20210205043924.149504-1-seanga2@gmail.com> Message-ID: <65bfe543-d9bf-ca5e-e1f9-6483ebe9049f@gmail.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 2/4/21 11:39 PM, Sean Anderson wrote: > This adds support for memory-mapped ("DIRMAP") reads (called XIP by the > datasheet). In theory, these have better performance than regular reads. In > practice, the CPU is already fast enough to max out the performance of this > peripheral. > > The real end-goal is to be able to boot a XIP kernel. This SoC has just barely > enough SRAM to boot Linux, and using a XIP kernel would decrease the memory > pressure to something tolerable. It would also probably absolutely *tank* the > performance, since not only is SPI flash ~8x slower than regular memory, there > is no cache to mitigate that latency. So it remains to be seen whether this is > worth it at all. > > This series is RFC because it currently reads all 1s on one board I have. On the > other board I have, it reads and writes fine. I will try and investigate this, > but I expect any changes to occur in "spi: dw: Add support for DIRMAP". Forgot to mention, but this series depends on [1]. A git branch with this complete series is available at [2]. [1] https://patchwork.ozlabs.org/project/uboot/list/?series=228123 [2] https://github.com/Forty-Bot/u-boot/tree/maix_xip > > Sean Anderson (13): > linux err: Synchronize with Linux 5.10 > spi-mem: Add dirmap API from Linux > mtd: spi-nor: use spi-mem dirmap API > core: ofnode: Fix inconsistent returns of *_read_u32_array > mux: Inline mux functions when CONFIG_MUX is disabled > mux: Define a stub for mux_get_by_index if CONFIG_MUX is disabled > mux: mmio: Only complain about idle-states if it is malformed > spi: dw: Define XIP registers > spi: dw: Add XIP and XIP_CONCURRENT caps > spi: dw: Use a mux to access registers > spi: dw: Add support for DIRMAP > riscv: k210: Increase SPI3 bus clock to CPU speed > riscv: k210: Add bindings for SPI XIP > > arch/riscv/dts/k210.dtsi | 25 ++- > drivers/core/ofnode.c | 15 +- > drivers/mtd/spi/sf_probe.c | 79 ++++++++ > drivers/mtd/spi/spi-nor-core.c | 45 +++-- > drivers/mux/mmio.c | 5 +- > drivers/spi/Kconfig | 10 + > drivers/spi/designware_spi.c | 337 +++++++++++++++++++++++++++++++-- > drivers/spi/spi-mem.c | 270 ++++++++++++++++++++++++++ > include/linux/err.h | 21 +- > include/linux/mtd/spi-nor.h | 6 + > include/mux.h | 25 ++- > include/spi-mem.h | 99 ++++++++++ > 12 files changed, 889 insertions(+), 48 deletions(-) >