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From: Mark Brown <broonie@kernel.org>
To: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
	linux-riscv@lists.infradead.org, Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	devicetree@vger.kernel.org, Serge Semin <fancer.lancer@gmail.com>,
	linux-spi@vger.kernel.org, Stephen Boyd <sboyd@kernel.org>,
	linux-clk@vger.kernel.org,
	Linus Walleij <linus.walleij@linaro.org>,
	linux-gpio@vger.kernel.org,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Sean Anderson <seanga2@gmail.com>
Subject: Re: [PATCH 04/32] spi: dw: Introduce polling device tree property
Date: Mon, 9 Nov 2020 16:04:32 +0000	[thread overview]
Message-ID: <20201109160432.GF6380@sirena.org.uk> (raw)
In-Reply-To: <20201107081420.60325-5-damien.lemoal@wdc.com>

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On Sat, Nov 07, 2020 at 05:13:52PM +0900, Damien Le Moal wrote:

> With boards that have slow interrupts context switch, and a fast device
> connected to a spi master, e.g. an SD card through mmc-spi, using
> dw_spi_poll_transfer() intead of the regular interrupt based
> dw_spi_transfer_handler() function is more efficient and can avoid a lot
> of RX FIFO overflow errors while keeping the device SPI frequency
> reasonnably high (for speed). Introduce the "polling" device tree
> property to allow requesting polled processing of transfer depending on
> the connected device while keeping the spi master interrupts property
> unschanged. E.g. device trees such as:

This isn't something that looks like it should be configured via DT as a
separate property, this is more of a tuning property as far as I can see
- even on the same hardware there might be cases where people prefer to
keep using interrupts but for example allow transfers to stall while
waiting for the interrupt controller giving lower throughput but more
CPU cycles available for other things.

Unfortunately we don't have any information about how much interrupt
latency we should expect which makes this a bit annoying.  I do see that
there's already some existing attempt in the DMA code to tune burst
sizes to avoid FIFO overflows - it looks like the hardware is doing
something unusual and possibly unfortunate here though I've never
looked at it so I'm not sure exactly what is going on there but perhaps
ther's some tuning that can be done in there?  TBH I'm not clear what
the failure mode is where we need software to service interrupts
promptly in the middle of a DMA transfer in the first place, that seems
really strange.

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  reply	other threads:[~2020-11-09 16:04 UTC|newest]

Thread overview: 132+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-07  8:13 [PATCH 00/32] RISC-V Kendryte K210 support improvments Damien Le Moal
2020-11-07  8:13 ` [PATCH 01/32] of: Fix property supplier parsing Damien Le Moal
2020-11-09 15:05   ` Serge Semin
2020-11-09 15:14   ` Andy Shevchenko
2020-11-09 17:44     ` Serge Semin
2020-11-09 20:52       ` Rob Herring
2020-11-07  8:13 ` [PATCH 02/32] spi: dw: Add support for 32-bits ctrlr0 layout Damien Le Moal
2020-11-07 13:28   ` Sean Anderson
2020-11-09 14:25   ` Serge Semin
2020-11-09 14:33     ` Sean Anderson
2020-11-09 14:35       ` Sean Anderson
2020-11-09 14:40       ` Andy Shevchenko
2020-11-09 14:41         ` Andy Shevchenko
2020-11-09 14:49           ` Sean Anderson
2020-11-09 15:10             ` Andy Shevchenko
2020-11-09 14:36     ` Andy Shevchenko
2020-11-09 17:56       ` Serge Semin
2020-11-07  8:13 ` [PATCH 03/32] spi: dw: Fix driving MOSI low while recieving Damien Le Moal
2020-11-07 13:30   ` Sean Anderson
2020-11-09 13:29   ` Mark Brown
2020-11-09 13:47     ` Sean Anderson
2020-11-09 14:14       ` Mark Brown
2020-11-09 14:48         ` Serge Semin
2020-11-09 16:45           ` Mark Brown
2020-11-09 19:19         ` Serge Semin
2020-11-09 19:40           ` Sean Anderson
2020-11-09 20:17             ` Serge Semin
2020-11-09 20:29               ` Mark Brown
2020-11-09 20:20           ` Mark Brown
2020-11-09 21:05             ` Serge Semin
2020-11-10 13:43               ` Mark Brown
2020-11-07  8:13 ` [PATCH 04/32] spi: dw: Introduce polling device tree property Damien Le Moal
2020-11-09 16:04   ` Mark Brown [this message]
2020-11-09 19:59   ` Serge Semin
2020-11-13  9:22     ` Damien Le Moal
2020-11-15 16:01       ` Serge Semin
2020-11-16  7:47         ` Damien Le Moal
2020-11-16 12:33           ` Mark Brown
2020-11-16 21:55           ` Serge Semin
2020-11-17 14:44             ` Damien Le Moal
2020-11-17 18:26               ` Serge Semin
2020-11-18  4:41                 ` Damien Le Moal
2020-11-18 15:16                   ` Serge Semin
2020-11-19  5:12                     ` Damien Le Moal
2020-11-19  8:51                       ` Serge Semin
2020-11-19  8:57                         ` Damien Le Moal
2020-11-07  8:13 ` [PATCH 05/32] spi: dw: Introduce DW_SPI_CAP_POLL_NODELAY Damien Le Moal
2020-11-09 14:03   ` Mark Brown
2020-11-09 20:45   ` Serge Semin
2020-11-07  8:13 ` [PATCH 06/32] spi: dw: Add support for the Kendryte K210 SoC Damien Le Moal
2020-11-07 13:31   ` Sean Anderson
2020-11-07 13:42     ` Damien Le Moal
2020-11-07 13:52       ` Sean Anderson
2020-11-09 14:15         ` Mark Brown
2020-11-13  8:00     ` Damien Le Moal
2020-11-09 21:21   ` Serge Semin
2020-11-09 21:39     ` Damien Le Moal
2020-11-09 21:55       ` Rob Herring
2020-11-09 22:00         ` Damien Le Moal
2020-11-09 23:07           ` Rob Herring
2020-11-10  0:35             ` Damien Le Moal
2020-11-07  8:13 ` [PATCH 07/32] dt-bindings: Update DW SPI device tree bindings Damien Le Moal
2020-11-07  8:13 ` [PATCH 08/32] riscv: Fix kernel time_init() Damien Le Moal
2020-11-12  7:21   ` Atish Patra
2020-11-13  7:31   ` Stephen Boyd
2020-11-07  8:13 ` [PATCH 09/32] riscv: Fix SiFive gpio probe Damien Le Moal
2020-11-10 14:39   ` Linus Walleij
2020-11-07  8:13 ` [PATCH 10/32] riscv: Fix sifive serial driver Damien Le Moal
2020-11-07  8:13 ` [PATCH 11/32] riscv: Enable interrupts during syscalls with M-Mode Damien Le Moal
2020-11-07  8:14 ` [PATCH 12/32] riscv: Automatically select sysctl config options Damien Le Moal
2020-11-07  8:14 ` [PATCH 13/32] riscv: Fix builtin DTB handling Damien Le Moal
2020-11-15  4:17   ` kernel test robot
2020-11-07  8:14 ` [PATCH 14/32] dt-bindings: Define all Kendryte K210 clock IDs Damien Le Moal
2020-11-07 13:33   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 15/32] dt-bindings: Define Kendryte K210 sysctl registers Damien Le Moal
2020-11-07 13:34   ` Sean Anderson
2020-11-09 21:59   ` Rob Herring
2020-11-09 22:10     ` Sean Anderson
2020-11-09 23:01       ` Rob Herring
2020-11-07  8:14 ` [PATCH 16/32] dt-bindings: Define Kendryte K210 pin functions Damien Le Moal
2020-11-07 13:38   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 17/32] dt-bindings: Define Kendryte K210 reset signals Damien Le Moal
2020-11-07 13:38   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 18/32] riscv: Add Kendryte K210 SoC clock driver Damien Le Moal
2020-11-07 13:48   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 19/32] riscv: Add Kendryte K210 SoC reset controller Damien Le Moal
2020-11-07 13:58   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 20/32] riscv: Add Kendryte K210 FPIOA pinctrl driver Damien Le Moal
2020-11-09 18:48   ` kernel test robot
2020-11-15  0:28   ` kernel test robot
2020-11-24  8:43   ` Linus Walleij
2020-11-24  8:53     ` Damien Le Moal
2020-11-29 21:33       ` Linus Walleij
2020-11-30  3:13         ` Damien Le Moal
2020-11-30  7:05           ` Serge Semin
2020-11-30  7:27             ` Damien Le Moal
2020-11-24  8:56     ` Damien Le Moal
2020-11-07  8:14 ` [PATCH 21/32] dt-bindings: Add Kendryte and Canaan vendor prefix Damien Le Moal
2020-11-07 14:03   ` Sean Anderson
2020-11-13  8:17     ` Damien Le Moal
2020-11-09 22:01   ` Rob Herring
2020-11-09 22:04     ` Damien Le Moal
2020-11-07  8:14 ` [PATCH 22/32] dt-binding: Document kendryte,k210-sysctl bindings Damien Le Moal
2020-11-07 14:05   ` Sean Anderson
2020-11-09 15:32   ` Rob Herring
2020-11-07  8:14 ` [PATCH 23/32] dt-binding: Document kendryte,k210-clk bindings Damien Le Moal
2020-11-07 14:05   ` Sean Anderson
2020-11-09 21:58   ` Rob Herring
2020-11-07  8:14 ` [PATCH 24/32] dt-bindings: Document kendryte,k210-fpioa bindings Damien Le Moal
2020-11-07 14:06   ` Sean Anderson
2020-11-09 15:32   ` Rob Herring
2020-11-09 15:36   ` Rob Herring
2020-11-09 15:45     ` Sean Anderson
2020-11-11 14:32       ` Rob Herring
2020-11-19 10:57       ` Geert Uytterhoeven
2020-11-19 11:22         ` Damien Le Moal
2020-11-07  8:14 ` [PATCH 25/32] dt-bindings: Document kendryte,k210-rst bindings Damien Le Moal
2020-11-07 14:07   ` Sean Anderson
2020-11-09 15:37   ` Rob Herring
2020-11-09 15:41   ` Rob Herring
2020-11-07  8:14 ` [PATCH 26/32] riscv: Update Kendryte K210 device tree Damien Le Moal
2020-11-07 14:08   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 27/32] riscv: Add SiPeed MAIX BiT board " Damien Le Moal
2020-11-07 14:13   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 28/32] riscv: Add SiPeed MAIX DOCK " Damien Le Moal
2020-11-07  8:14 ` [PATCH 29/32] riscv: Add SiPeed MAIX GO " Damien Le Moal
2020-11-07  8:14 ` [PATCH 30/32] riscv: Add SiPeed MAIXDUINO " Damien Le Moal
2020-11-07 14:14   ` Sean Anderson
2020-11-07  8:14 ` [PATCH 31/32] riscv: Add Kendryte KD233 " Damien Le Moal
2020-11-07  8:14 ` [PATCH 32/32] riscv: Update Kendryte K210 defconfig Damien Le Moal
2020-11-09 12:51 ` [PATCH 00/32] RISC-V Kendryte K210 support improvments Mark Brown
2020-11-09 12:55   ` Damien Le Moal

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