linux-kernel - Re: [PATCH V5 3/3] spi: spi-geni-qcom: Add SPI driver support for GENI based QUP

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Date:   Thu, 11 Oct 2018 12:43:56 +0530
From:   alokc@...eaurora.org
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     broonie@...nel.org, dianders@...omium.org,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        mka@...omium.org, linux-arm-msm@...r.kernel.org,
        Girish Mahadevan <girishm@...eaurora.org>,
        Dilip Kota <dkota@...eaurora.org>
Subject: Re: [PATCH V5 3/3] spi: spi-geni-qcom: Add SPI driver support for
 GENI based QUP

>> +static irqreturn_t geni_spi_isr(int irq, void *data)
>> +{
>> +       struct spi_master *spi = data;
>> +       struct spi_geni_master *mas = spi_master_get_devdata(spi);
>> +       struct geni_se *se = &mas->se;
>> +       u32 m_irq;
>> +       unsigned long flags;
>> +       irqreturn_t ret = IRQ_HANDLED;
>> +
>> +       if (mas->cur_mcmd == CMD_NONE)
>> +               return IRQ_NONE;
>> +
>> +       spin_lock_irqsave(&mas->lock, flags);
>> +       m_irq = readl(se->base + SE_GENI_M_IRQ_STATUS);
>> +
>> +       if ((m_irq & M_RX_FIFO_WATERMARK_EN) || (m_irq & 
>> M_RX_FIFO_LAST_EN))
>> +               geni_spi_handle_rx(mas);
>> +
>> +       if (m_irq & M_TX_FIFO_WATERMARK_EN)
>> +               geni_spi_handle_tx(mas);
>> +
>> +       if (m_irq & M_CMD_DONE_EN) {
>> +               if (mas->cur_mcmd == CMD_XFER)
>> +                       spi_finalize_current_transfer(spi);
>> +               else if (mas->cur_mcmd == CMD_CS)
>> +                       complete(&mas->xfer_done);
>> +               mas->cur_mcmd = CMD_NONE;
>> +               /*
>> +                * If this happens, then a CMD_DONE came before all 
>> the Tx
>> +                * buffer bytes were sent out. This is unusual, log 
>> this
>> +                * condition and disable the WM interrupt to prevent 
>> the
>> +                * system from stalling due an interrupt storm.
>> +                * If this happens when all Rx bytes haven't been 
>> received, log
>> +                * the condition.
>> +                * The only known time this can happen is if 
>> bits_per_word != 8
>> +                * and some registers that expect xfer lengths in num 
>> spi_words
>> +                * weren't written correctly.
>> +                */
>> +               if (mas->tx_rem_bytes) {
>> +                       writel(0, se->base + 
>> SE_GENI_TX_WATERMARK_REG);
>> +                       dev_err(mas->dev, "Premature done. tx_rem = %d 
>> bpw%d\n",
>> +                               mas->tx_rem_bytes, 
>> mas->cur_bits_per_word);
>> +               }
>> +               if (mas->rx_rem_bytes)
>> +                       dev_err(mas->dev, "Premature done. rx_rem = %d 
>> bpw%d\n",
>> +                               mas->rx_rem_bytes, 
>> mas->cur_bits_per_word);
>> +       }
>> +
>> +       if ((m_irq & M_CMD_CANCEL_EN) || (m_irq & M_CMD_ABORT_EN)) {
>> +               mas->cur_mcmd = CMD_NONE;
>> +               complete(&mas->xfer_done);
>> +       }
>> +
>> +       writel(m_irq, se->base + SE_GENI_M_IRQ_CLEAR);
>> +       spin_unlock_irqrestore(&mas->lock, flags);
>> +       return ret;
> 
> Nitpick: Now this always returns IRQ_HANDLED, and we assign ret just to
> do that. Perhaps only return IRQ_HANDLED if one of the above if
> conditions is taken?

Not always. If ISR get triggered without setting proper cur_mcmd then it 
will return IRQ_NONE.