Re: [PATCH] spi: meson-spicc: add DMA support

[neil.armstrong@linaro.org]

On 14/04/2025 05:56, Da Xue wrote:
> On Sun, Apr 13, 2025 at 11:14 PM Xianwei Zhao <xianwei.zhao@amlogic.com> wrote:
>>
>> Hi Neil,
>>      Thanks for your reply.
>>
>> On 2025/4/9 20:35, neil.armstrong@linaro.org wrote:
>>>
>>> Hi,
>>>
>>> On 09/04/2025 03:49, Xianwei Zhao wrote:
>>>> Hi Neil,
>>>>      Thanks for your reply.
>>>>
>>>> On 2025/4/8 15:41, Neil Armstrong wrote:
>>>>> [ EXTERNAL EMAIL ]
>>>>>
>>>>> Hi,
>>>>>
>>>>> On 08/04/2025 09:04, Xianwei Zhao via B4 Relay wrote:
>>>>>> From: Xianwei Zhao <xianwei.zhao@amlogic.com>
>>>>>>
>>>>>> Add DMA support for spicc driver.
>>>>>>
>>>>>> DMA works if the transfer meets the following conditions:
>>>>>> 1. 64 bits per word;
>>>>>> 2. The transfer length must be multiples of the dma_burst_len,
>>>>>>      and the dma_burst_len should be one of 8,7...2,
>>>>>>      otherwise, it will be split into several SPI bursts.
>>>>>>
>>>>>> Signed-off-by: Sunny Luo <sunny.luo@amlogic.com>
>>>>>> Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
>>>>>> ---
>>>>>>    drivers/spi/spi-meson-spicc.c | 243
>>>>>> ++++++++++++++++++++++++++++++++++++++++--
>>>>>>    1 file changed, 232 insertions(+), 11 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/spi/spi-meson-spicc.c
>>>>>> b/drivers/spi/spi-meson-spicc.c
>>>>>> index df74ad5060f8..81e263bceba9 100644
>>>>>> --- a/drivers/spi/spi-meson-spicc.c
>>>>>> +++ b/drivers/spi/spi-meson-spicc.c
>>>>>> @@ -21,6 +21,7 @@
>>>>>>    #include <linux/interrupt.h>
>>>>>>    #include <linux/reset.h>
>>>>>>    #include <linux/pinctrl/consumer.h>
>>>>>> +#include <linux/dma-mapping.h>
>>>>>>
>>>>>>    /*
>>>>>>     * The Meson SPICC controller could support DMA based transfers,
>>>>>> but is not
>>>>>> @@ -33,6 +34,20 @@
>>>>>>     * - CS management is dumb, and goes UP between every burst, so is
>>>>>> really a
>>>>>>     *   "Data Valid" signal than a Chip Select, GPIO link should be
>>>>>> used instead
>>>>>>     *   to have a CS go down over the full transfer
>>>>>> + *
>>>>>> + * DMA achieves a transfer with one or more SPI bursts, each SPI
>>>>>> burst is made
>>>>>> + * up of one or more DMA bursts. The DMA burst implementation
>>>>>> mechanism is,
>>>>>> + * For TX, when the number of words in TXFIFO is less than the preset
>>>>>> + * reading threshold, SPICC starts a reading DMA burst, which reads
>>>>>> the preset
>>>>>> + * number of words from TX buffer, then writes them into TXFIFO.
>>>>>> + * For RX, when the number of words in RXFIFO is greater than the
>>>>>> preset
>>>>>> + * writing threshold, SPICC starts a writing request burst, which
>>>>>> reads the
>>>>>> + * preset number of words from RXFIFO, then write them into RX buffer.
>>>>>> + * DMA works if the transfer meets the following conditions,
>>>>>> + * - 64 bits per word
>>>>>> + * - The transfer length in word must be multiples of the
>>>>>> dma_burst_len, and
>>>>>> + *   the dma_burst_len should be one of 8,7...2, otherwise, it will
>>>>>> be split
>>>>>> + *   into several SPI bursts by this driver
>>>>>
>>>>> Fine, but then also rephrase the previous paragraph since you're
>>>>> adding DMA.
>>>>>
>>>> Will do.
>>>>
>>>>> Could you precise on which platform you tested the DMA ?
>>>>>
>>>>
>>>> aq222(S4)
>>>
>>> Will you be able to test on other platforms ?
>>>
>>
>> I tested it on other platforms over the last few days. G12A and C3 and
>> T7(T7 CLOCK use local source).
>>
>> My board SPI does not connect peripherals and is tested through a
>> hardware loop.
> 
> I can test it on GXL and SM1 in the next two weeks against a SPI
> display and some WS2812B LCDs.

Would be great, thx !

Neil

> 
>> cmd:
>> spi_test -D /dev/spidev0.0 -v -s 5000000 -b 64 -l
>>
>>>>
>>>>>>     */
>>>>>>
<snip>