From: Akash Asthana <akashast@codeaurora.org>
To: Stephen Boyd <swboyd@chromium.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Douglas Anderson <dianders@chromium.org>,
Wolfram Sang <wsa@kernel.org>
Cc: linux-arm-msm@vger.kernel.org, linux-i2c@vger.kernel.org,
Andy Gross <agross@kernel.org>,
Girish Mahadevan <girishm@codeaurora.org>,
Karthikeyan Ramasubramanian <kramasub@codeaurora.org>,
Mukesh Kumar Savaliya <msavaliy@codeaurora.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] soc: qcom: geni: More properly switch to DMA mode
Date: Mon, 12 Oct 2020 14:35:23 +0530 [thread overview]
Message-ID: <2ccc26a0-5d54-e06c-5a73-7eb353c393d2@codeaurora.org> (raw)
In-Reply-To: <160229038385.310579.7502548054994849649@swboyd.mtv.corp.google.com>
Hi Stephen,
>>
>> static void geni_se_select_dma_mode(struct geni_se *se)
>> {
>> + u32 proto = geni_se_read_proto(se);
>> u32 val;
>>
>> geni_se_irq_clear(se);
>>
>> + val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN);
>> + if (proto != GENI_SE_UART) {
> Not a problem with this patch but it would be great if there was a
> comment here (and probably in geni_se_select_fifo_mode() too) indicating
> why GENI_SE_UART is special. Is it because GENI_SE_UART doesn't use the
> main sequencer? I think that is the reason, but I forgot and reading
> this code doesn't tell me that.
>
> Splitting the driver in this way where the logic is in the geni wrapper
> and in the engine driver leads to this confusion.
GENI_SE_UART uses main sequencer for TX and secondary for RX transfers
because it is asynchronous in nature.
That's why RX related bits (M_RX_FIFO_WATERMARK_EN |
M_RX_FIFO_LAST_EN) are not enable in main sequencer for UART.
(M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN) bits are controlled from UART
driver, it's gets enabled and disabled multiple times from start_tx
,stop_tx respectively.
Regards,
Akash
>
>> + val &= ~(M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN);
>> + val &= ~(M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN);
>> + }
>> + writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN);
>> +
>> + val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN);
>> + if (proto != GENI_SE_UART)
>> + val &= ~S_CMD_DONE_EN;
>> + writel_relaxed(val, se->base + SE_GENI_S_IRQ_EN);
>> +
>> val = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN);
>> val |= GENI_DMA_MODE_EN;
>> writel_relaxed(val, se->base + SE_GENI_DMA_MODE_EN);
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,\na Linux Foundation Collaborative Project
next prev parent reply other threads:[~2020-10-12 9:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-08 22:52 [PATCH 0/3] i2c: i2c-qcom-geni: More properly fix the DMA race Douglas Anderson
2020-10-08 22:52 ` [PATCH 1/3] soc: qcom: geni: More properly switch to DMA mode Douglas Anderson
2020-10-10 0:39 ` Stephen Boyd
2020-10-12 9:05 ` Akash Asthana [this message]
2020-10-13 21:35 ` Doug Anderson
2020-10-12 8:09 ` Akash Asthana
2020-10-08 22:52 ` [PATCH 2/3] Revert "i2c: i2c-qcom-geni: Fix DMA transfer race" Douglas Anderson
2020-10-10 0:39 ` Stephen Boyd
2020-10-12 8:12 ` Akash Asthana
2020-10-08 22:52 ` [PATCH 3/3] soc: qcom: geni: Optimize select fifo/dma mode Douglas Anderson
2020-10-10 0:32 ` Stephen Boyd
2020-10-13 21:38 ` Doug Anderson
2020-10-10 0:26 ` [PATCH 0/3] i2c: i2c-qcom-geni: More properly fix the DMA race Stephen Boyd
2020-10-10 13:16 ` Dmitry Baryshkov
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